#### Sample records for fatigue life expenditure

1. Long-Term Fatigue Life Expenditure of Turbine Shafts Owing to Noncharacteristic Harmonics Produced by Slip Energy Recovery Induction Motor Drives

Science.gov (United States)

Tsai, Jong-Ian

In this paper, the long-term effect of noncharacteristic harmonics resulting from a slip energy recovery induction motor drive (SERIMD) on the fatigue life expenditure of turbine-generator shafts is analyzed. A feed-water pump (FP) in power plants is one of the most essential pieces of auxiliary equipment and consumes considerably large quantities of energy. An SERIMD has many advantages and is an adequate candidate for the purpose of variable speed control. However, it gives rise to sustainable variable frequency subharmonics which induce electromechanical subsynchronous oscillations in turbine shafts through proposed deductions. Accordingly, the author has determined that the long-term effect of these subharmonics is a cause of fatigue damage on turbine shafts even under normal operating conditions through fatigue life estimation.

2. Fatigue life extension

Science.gov (United States)

Matejczyk, D. E.; Lin, J.

1985-01-01

Potential fatigue rejuvenation processes were carried out on fatigue-damaged material both with and without observable surface-connected fatigue cracks. The fatigue life of fatigue-damaged MAR-M246(Hf)(DS), a directionally solidified nickel-base superalloy used in turbine airfoils, was extended by reheat treatment. The fatigue life of fatigue-cracked Inconel 718, a wrought nickel-base superalloy used in a wide variety of advanced rocket engine components, was extended by electron-beam welding to close off the surface-connected crack, followed by hot isostatic pressing and reheat treatment.

3. Energy expenditure characteristics of weight lifting: 2 sets to fatigue.

Science.gov (United States)

Scott, Christopher B; Leary, Michael P; Tenbraak, Andrew J

2011-02-01

We investigated the work performed and energy expenditure characteristics within and among 2 sets of the bench press at 70%, 80%, and 90% of 1 repetition maximum (1RM). For both sets fatigue was the end point. We asked: do multiple sets affect subsequent work output along with aerobic, anaerobic, and excess postexercise oxygen consumption (EPOC) contributions? Ten males participated. Work was significantly less for the 2nd set within the 70% and 80% protocols, but not the 90% protocol. Anaerobic (glycolytic) energy expenditure was less for the 2nd set within all protocols. However, within all protocols, the work / energy expenditure ratio was not different between sets. Overall work was significantly different among protocols, becoming less as the weight lifted was increased: 70%, 637.1 ± 122.4 J; 80%, 512.4 ± 93.4 J; 90%, 324.7 ± 92.6 J (p EPOC was not different among protocols after the 1st set, 2nd set, or combined overall. Moreover, the overall EPOC did not correlate with overall work performed (r = 0.31, p = 0.11). EPOC overall did correlate with aerobic (r = 0.68, p EPOC that is similar for all. As more work is completed (i.e., lower weight, more repetitions), aerobic and anaerobic exercise energy expenditures appear to increase accordingly, yet absolute EPOC remains essentially unchanged, contributing less to the overall energy expenditure.

4. MODELS OF FATIGUE LIFE CURVES IN FATIGUE LIFE CALCULATIONS OF MACHINE ELEMENTS – EXAMPLES OF RESEARCH

Directory of Open Access Journals (Sweden)

Grzegorz SZALA

2014-03-01

Full Text Available In the paper there was attempted to analyse models of fatigue life curves possible to apply in calculations of fatigue life of machine elements. The analysis was limited to fatigue life curves in stress approach enabling cyclic stresses from the range of low cycle fatigue (LCF, high cycle fatigue (HCF, fatigue limit (FL and giga cycle fatigue (GCF appearing in the loading spectrum at the same time. Chosen models of the analysed fatigue live curves will be illustrated with test results of steel and aluminium alloys.

5. Fatigue life prediction in composites

CSIR Research Space (South Africa)

Huston, RJ

1994-01-01

Full Text Available as the modulus is measured accurately. Its main disadvantage is that it can be applied only to constant amplitude fatigue loadings. REFERENCES 1. Mandell, J. F., Huang, D. D. & McGarry, F. J., Tensile fatigue performance...

6. Terminal costs, improved life expectancy and future public health expenditure.

Science.gov (United States)

Bjørner, Thomas Bue; Arnberg, Søren

2012-06-01

This paper presents an empirical analysis of public health expenditure on individuals in Denmark. The analysis separates out the individual effects of age and proximity to death (reflecting terminal costs of dying) and employs unique micro data from the period 2000 to 2009, covering a random sample of 10% of the Danish population. Health expenditure includes treatment in hospitals, subsidies to prescribed medication and health care provided by general practitioners and specialists and covers about 80% of public health care expenditure on individuals. The results confirm findings from previous studies showing that proximity to death has a significant impact on health care expenditure. However, it is also found that cohort effects (the baby boom generation) as well as improvements in life expectancy have a substantial effect on future health care expenditure even when proximity to death is controlled for. These results are obtained by combining the empirical estimates with a long term population forecast. When life expectancy increases, terminal costs are postponed but the increases in health expenditure that follow from longer life expectancy are not as large as the increase in the number of elderly persons would suggest (due to "healthy ageing"). Based on the empirical estimates, healthy ageing is expected to reduce the impact of increased life expectancy on real health expenditure by 50% compared to a situation without healthy ageing.

7. LIFE PREDICTION APPROACH FOR RANDOM MULTIAXIAL FATIGUE

Institute of Scientific and Technical Information of China (English)

Wang Lei; Wang Dejun

2005-01-01

According to the concept of critical plane, a life prediction approach for random multiaxial fatigue is presented. First, the critical plane under the multiaxial random loading is determined based on the concept of the weight-averaged maximum shear strain direction. Then the shear and normal strain histories on the determined critical plane are calculated and taken as the subject of multiaxial load simplifying and multiaxial cycle counting. Furthermore, a multiaxial fatigue life prediction model including the parameters resulted from multiaxial cycle counting is presented and applied to calculating the fatigue damage generated from each cycle. Finally, the cumulative damage is added up using Miner's linear rule, and the fatigue prediction life is given. The experiments under multiaxial loading blocks are used for the verification of the proposed method. The prediction has a good correction with the experimental results.

8. The probability distribution of fatigue damage and the statistical moment of fatigue life

Institute of Scientific and Technical Information of China (English)

熊峻江; 高镇同

1997-01-01

The randomization of deterministic fatigue damage equation leads to the stochastic differential equation and the Fokker-Planck equation affected by random fluctuation. By means of the solution of equation, the probability distribution of fatigue damage with the change of time is obtained. Then the statistical moment of fatigue life in consideration of the stationary random fluctuation is derived. Finally, the damage probability distributions during the fatigue crack initiation and fatigue crack growth are given

9. Fatigue Analysis and Life Prediction of Dumpers with Cumulative Fatigue Damage Approach

Institute of Scientific and Technical Information of China (English)

LI Shouju; LIU Yingxi; SUN Huiling

2004-01-01

A fatigue damage model is developed for evaluating accumulative fatigue damage of dumpers. The loading spectrums acted on dumpers are created according to measured strain data in field. The finite element analysis is carried out for assessing stress distribution and strength characteristics of dumpers. Fatigue damage indexes and service life are calculated by a modified Palmgren-Miner rule. The investigation shows that fatigue notch factor has a significant influence on the calculation of fatigue damage of dumpers.

10. Low-Cycle Fatigue Life and Fatigue Crack Propagation of Sintered Ag Nanoparticles

Science.gov (United States)

Shioda, Ryutaro; Kariya, Yoshiharu; Mizumura, Noritsuka; Sasaki, Koji

2017-02-01

The low-cycle fatigue life and fatigue crack propagation behavior of sintered silver nanoparticles were investigated using miniature specimens sintered at two different temperatures. The fatigue crack initiation life and fatigue crack propagation rate of sintered Ag nanoparticles were extremely sensitive to changes in the range of inelastic energy density and the cyclic J integral, exhibiting brittle characteristics, in contrast to tin-based lead-free solder alloys. With increasing sintering temperature, the fatigue crack propagation rate decreased. On the other hand, the effect of sintering temperature on the fatigue crack initiation life differed depending on the use of either a smooth specimen (low-cycle fatigue test) or notched specimen (fatigue crack propagation test). For the notched specimens, the probability of grain boundaries around the notch decreased due to increased sintering temperature. Therefore, the fatigue crack initiation life was increased with an increase in sintering temperature in the fatigue crack propagation test. In the smooth specimen, however, the fatigue life decreased with an increase in sintering temperature, as the elastic modulus of the specimen increased with increasing sintering temperature. In the low-cycle fatigue test, the specimen sintered with high internal stress started to develop crack initiation early, causing a decrease in the crack initiation life.

11. A predictive fatigue life model for anodized 7050 aluminium alloy

OpenAIRE

2013-01-01

International audience; The objective of this study is to predict fatigue life of anodized 7050 aluminum alloy specimens. In the case of anodized 7050-T7451 alloy, fractographic observations of fatigue tested specimens showed that pickling pits were the predominant sites for crack nucleation and subsequent failure. It has been shown that fatigue failure was favored by the presence of multiple cracks. From these experimental results, a fatigue life predictive model has been developed including...

12. Fatigue life of metal treated by magnetic field

Institute of Scientific and Technical Information of China (English)

Liu Zhao-Long; Hu Hai-Yun; Fan Tian-You; Xing Xiu-San

2009-01-01

This paper investigates theoretically the influence of magnetization on fatigue life by using non-equilibrium statis-tical theory of fatigue fracture for metals. The fatigue microcrack growth rate is obtained from the dynamic equation of microcrack growth, where the influence of magnetization is described by an additional term in the potential energy of microcrack. The statistical value of fatigue life of metal under magnetic field is derived, which is expressed in terms of magnetic field and macrophysical as well as microphysical quantities. The fatigue life of AISI 4140 steel in static magnetic field from this theory is basically consistent with the experimental data.

13. Research on fatigue life expenditure and torsional vibration check of a 600 MW unit under subsynchronous oscillation%600 MW机组次同步振荡下轴系扭振校核及疲劳寿命损耗计算

Institute of Scientific and Technical Information of China (English)

崔亚辉; 张俊杰; 顾煜炯; 金铁铮; 孙鹏; 渠福来; 范景利

2016-01-01

Low-amplitude subsynchronous oscillation (SSO)problem occurred frequently during operation of a supercritical 600 MW unit.To solve this problem,the Riccati transfer matrix method was applied to es-tablish lumped-mass model for this unit.The torsional vibration natural frequency of shafting was solved, and the result was compared with the actual measured torsional vibration natural frequency of shafting.It was proved that the calculation results agreed well with the actual measured results,this model could be used to analyze the torsional vibration of this unit.Moreover,the relative value of torsional vibration stress shafting was solved based on the torsional vibration mode of this unit shafting,and the dangerous section of shafting was determined under SSO.The relationship between speed difference of the unit head and the fa-tigue life of the most dangerous section under SSO was established,the torsional vibration safety and fa-tigue life expenditure of the unit when the low-amplitude SSO occurred were evaluated.It provides impor-tant references for the same type units to analyze SSO.%针对某超临界600 MW机组在运行过程中经常出现的低振幅次同步振荡(SSO)问题，本文采用Riccati传递矩阵法建立了该机组的集中质量模型，求解了轴系的扭振固有频率，并与轴系的实测扭振固有频率进行了对比，证明了该模型计算结果与实测结果相符，可用于机组扭振分析。同时，应用本文模型，根据该机组轴系的扭振振型求解了轴系的扭振应力相对值，确定了SSO下轴系的危险截面；建立了次同步振荡下机头转速差与最危险截面疲劳寿命之间的关系，可对该机组发生低振幅SSO时的扭振安全性和疲劳寿命损耗进行评估。

Institute of Scientific and Technical Information of China (English)

Y.Noguchi; M.Miyahara

2004-01-01

A new method was proposed for the multiaxial creep-fatigue life evaluation under proportional loadings. Because this method was derived from the strain range partitioning method with a multiaxiality factor, it was possible to consider the influence of both creep-fatigue interaction and multiaxial stress state on fatigue life. In order to predict the combined axial-torsional fatigue life the damage under combined loading was defined as linear summation of the damages under axial loading and torsional loading.Axial-torsional creep-fatigue tests were carried out using tubular specimens of 316LC austenitic stainless steel and the ferritic rotor steel. This rotor steel was developed for the permanent magnet type eddy current retarder in heavy trucks. Experimentally obtained lives of both steels were well corresponded with the lives predicted by the proposed method. It was found that the proposed method was effective in multiaxial fatigue life evaluation under proportional creep-fatigue loadings.

15. Forecasting method of fatigue life test data for metal materials

Institute of Scientific and Technical Information of China (English)

张怀亮; 邱显焱; 谭冠军

2001-01-01

GM(1, 1) model of grey system theory is used to forecast fatigue life test data for metal materials. The method can reduce test time and save test cost, and reliability indexes of metal materials can be obtained quickly. The results of an example show that grey system theory has a high precision for forecasting fatigue life test data for metal materials. A valuable method is put forward, which can effectively reduce the fatigue life test time for metal materials.

16. Towards a unified fatigue life prediction method for marine structures

CERN Document Server

Cui, Weicheng; Wang, Fang

2014-01-01

In order to apply the damage tolerance design philosophy to design marine structures, accurate prediction of fatigue crack growth under service conditions is required. Now, more and more people have realized that only a fatigue life prediction method based on fatigue crack propagation (FCP) theory has the potential to explain various fatigue phenomena observed. In this book, the issues leading towards the development of a unified fatigue life prediction (UFLP) method based on FCP theory are addressed. Based on the philosophy of the UFLP method, the current inconsistency between fatigue design and inspection of marine structures could be resolved. This book presents the state-of-the-art and recent advances, including those by the authors, in fatigue studies. It is designed to lead the future directions and to provide a useful tool in many practical applications. It is intended to address to engineers, naval architects, research staff, professionals and graduates engaged in fatigue prevention design and survey ...

17. Conductor fatigue-life research. Final report

Energy Technology Data Exchange (ETDEWEB)

Ramey, G.E.

1981-07-01

This is the final report of Research Project RP 1278-1 sponsored by the Electric Power Research Institute and carried out at the Civil Engineering Department of Auburn University (Auburn, Alabama). The objective of this study was to evaluate the effects of reducing vibration amplitudes of ACSR conductors which had been minimally damaged by aeolian vibration. The aeolian vibration was simulated by mechanical means in a controlled laboratory situation and the reduction in vibration amplitudes was a simulation of the addition of amplitude limiting devices (dampers). Conductors were vibrated at high amplitudes until a predetermined number of strand breaks occurred, after which the vibration was continued at reduced amplitudes. Three different ACSB conductors were tested: 795 KCM 26/7, 795 KCM 45/7, and 397.5 KCM 26/7. These conductors were chosen to establish the effects of conductor size and stranding on the amplitude reduction tests. Two different amplitude reductions were used to establish a threshold value for a maximum reduced amplitude. Previous preliminary research by others indicated that amplitude reductions extended the working life of conductors. This research expanded the amplitude reduction values and conductor sizes and strandings tested. For each set of parameters, four duplicative tests were performed to give statistical credence to the data. The results of the investigation indicated that amplitude reductions arrested fatigue strand breakage in each case. Electric utilities can utilize the results of this EPRI project in assessing the fatigue life of minimally damaged transmisson lines and in evaluating techniques for mitigating fatigue damage.

18. Calculation of the fatigue life distribution of a composite laminate

Energy Technology Data Exchange (ETDEWEB)

Anderson, IA.A.; Limonov, V.A. (AN LSSR, Institut Mekhaniki Polimerov, Riga, Latvian (USSR))

1991-02-01

A method based on a probabilistic interpretation of the Hashin criterion is proposed for calculating the fatigue life distributions of a unidirectional composite under conditions of a plane stressed state from test results obtained for simple loading schemes. By using the linear damage accumulation law, an estimate is obtained of the scatter of the composite fatigue life related to the scatter of the material fatigue strength. A procedure is then presented for estimating the fatigue life distribution of a composite laminate in the plane stressed state based on layer-by-layer fracture analysis using the linear damage summation law and the determining layer concept. 26 refs.

19. Fatigue life characterization for piezoelectric macrofiber composites

Science.gov (United States)

Henslee, Isaac A.; Miller, David A.; Tempero, Tyler

2012-10-01

In an effort to aid the investigation into lightweight and reliable materials for actuator design, a study was developed to characterize the temperature-dependent lifetime performance of a piezoelectric macrofiber composite (MFC). MFCs are thin rectangular patches of polyimide film, epoxy and a single layer of rectangular lead zirconium titanate (PZT) fibers. In this study, the useful life of the MFC is characterized to determine the effect of temperature on the performance of the composite as it is fatigued by cyclic piezoelectric excitation. The test specimen consists of the MFC laminated to a cantilevered stainless steel beam. Beam strain and tip displacement measurements are used as a basis for determining the performance of the MFC as it is cyclically actuated under various operating temperatures. The temperature of the beam laminate is held constant and then cycled to failure, or 250 million cycles, in order to determine the useful life of the MFC over a temperature range from - 15 to 145 °C. The results of the experiments show a strong temperature dependence of the operational life for the MFC. Damage inside the composite was identified through in situ visual inspection and during post-test microstructural observation; however, no degradation in operational performance was identified as it was cyclically actuated up to the point of failure, regardless of temperature or actuation cycle number.

20. How surface damage removal affects fatigue life

Science.gov (United States)

Jeelani, S.; Scott, M. A.

1988-01-01

The effect of the removal of work hardened surface layers from specimens of 2024-T4 aluminum alloy and AISI-4130 steel on their fatigue lives has been investigated. Specimens were fatigued at selected stress levels for a given number of cycles, and the surface layer was removed followed by subsequent fatigue cycling. Results confirm that when a material is subjected to fatigue loading, damage accumulates in the surface layers in the form of work hardening. Removal of the surface layer brings the specimen back to its pre-fatigued condition.

1. Fracture Mechanics Prediction of Fatigue Life of Aluminum Highway Bridges

DEFF Research Database (Denmark)

Rom, Søren; Agerskov, Henning

2015-01-01

Fracture mechanics prediction of the fatigue life of aluminum highway bridges under random loading is studied. The fatigue life of welded joints has been determined from fracture mechanics analyses and the results obtained have been compared with results from experimental investigations. The fati......Fracture mechanics prediction of the fatigue life of aluminum highway bridges under random loading is studied. The fatigue life of welded joints has been determined from fracture mechanics analyses and the results obtained have been compared with results from experimental investigations...... against fatigue in aluminum bridges, may give results which are unconservative. Furthermore, it was in both investigations found that the validity of the results obtained from Miner's rule will depend on the distribution of the load history in tension and compression....

2. Flexural fatigue life prediction of closed hat-section using materially nonlinear axial fatigue characteristics

Science.gov (United States)

Razzaq, Zia

1989-01-01

Straight or curved hat-section members are often used as structural stiffeners in aircraft. For instance, they are employed as stiffeners for the dorsal skin as well as in the aerial refueling adjacent area structure in F-106 aircraft. The flanges of the hat-section are connected to the aircraft skin. Thus, the portion of the skin closing the hat-section interacts with the section itself when resisting the stresses due to service loads. The flexural fatigue life of such a closed section is estimated using materially nonlinear axial fatigue characteristics. It should be recognized that when a structural shape is subjected to bending, the fatigue life at the neutral axis is infinity since the normal stresses are zero at that location. Conversely, the fatigue life at the extreme fibers where the normal bending stresses are maximum can be expected to be finite. Thus, different fatigue life estimates can be visualized at various distances from the neural axis. The problem becomes compounded further when significant portions away from the neutral axis are stressed into plastic range. A theoretical analysis of the closed hat-section subjected to flexural cyclic loading is first conducted. The axial fatigue characteristics together with the related axial fatigue life formula and its inverted form given by Manson and Muralidharan are adopted for an aluminum alloy used in aircraft construction. A closed-form expression for predicting the flexural fatigue life is then derived for the closed hat-section including materially nonlinear action. A computer program is written to conduct a study of the variables such as the thicknesses of the hat-section and the skin, and the type of alloy used. The study has provided a fundamental understanding of the flexural fatigue life characteristics of a practical structural component used in aircraft when materially nonlinear action is present.

3. Bayesian inference model for fatigue life of laminated composites

DEFF Research Database (Denmark)

Dimitrov, Nikolay Krasimirov; Kiureghian, Armen Der; Berggreen, Christian

2016-01-01

A probabilistic model for estimating the fatigue life of laminated composite plates is developed. The model is based on lamina-level input data, making it possible to predict fatigue properties for a wide range of laminate configurations. Model parameters are estimated by Bayesian inference...

4. Reducing Uncertainty in Fatigue Life Limits of Turbine Engine Alloys

Science.gov (United States)

2014-03-01

this behavior in turbine engine alloys , we have developed a physically- based approach for describing fatigue var- iability, and this approach has been...of competing mechanisms in the fatigue life variability of a nearly fully-lamellar c-TiAl based alloy . Acta Mater 2005;53:1293–304. [50] Buchanan DJ...Burns JT, Larsen JM, Gangloff RP. Driving forces for localized corrosion -to- fatigue crack transition in Al–Zn– Mg –Cu. Fatigue Fract Eng Mater Struct

5. Fatigue Life of High-Strength Steel Offshore Tubular Joints

DEFF Research Database (Denmark)

Petersen, Rasmus Ingomar; Agerskov, Henning; Lopez Martinez, Luis

1996-01-01

In the present investigation, the fatigue life of tubular joints in offshore steel structures is studied. Two test series on full-scale tubular joints have been carried through. One series was on joints in conventional offshore structural steel, and the other series was on joints in high-strength...... steel with a yield stress of 820-830 MPa and with high weldability and toughness properties. The test specimens of both series had the same geometry. The present report concentrates on the results obtained in the investigation on the high-strength steel tubular joints.The test specimens were fabricated...... amplitude fatigue test results showed shorter fatigue lives in variable amplitude loading than should be expected from the linear fatigue damage accumulation formula. Furthermore, the fatigue tests on high-strength steel tubular joints showed slightly longer fatigue lives than those obtained...

6. Effect of undernutrition in foetal life on energy expenditure during gestation in ewes

DEFF Research Database (Denmark)

Kiani, Alishir; Chwalibog, André; Tygesen, Malin P;

2008-01-01

The long-term effect of early life undernutrition on late gestation energy expenditure (EEgest) was investigated in sheep. Ewes were fed either adequate (100%) or restricted (60%) energy and protein during late foetal life as well as during last trimester of gestation later in life, resulting in ...... nutrient restriction in early life impairs the ability of ewes to respond to nutritional restriction in terms of energy expenditure of gestation....

7. Fatigue Life Analysis of Cantilever Probe on Wafer Test

Directory of Open Access Journals (Sweden)

Hsiao Te-Ching

2016-01-01

Full Text Available This research utilizes the finite element analysis software (ANSYS to stimulate the different probe material quality (tungsten, SUS304 stainless steel, SUS316L stainless steel and SKD11 tool steel, respectively during wafer tests. Under a room temperature of (25°C, the stress and fatigue life (cycles of probing test of the cantilever probe were measured with an OverDriver (OD of 20µm, 40µm, 50µm, 60µm and 80µm, respectively. First, to obtain the magnitude of pinpoint shift of the probe under wafer test and the OverDriver is 50µm. And, calculate the fatigue life of the probe. Then, a probe model with the same characteristics as the experiment is created and the probe fatigue life analyzed with the ANSYS. After the reliability of the model is ascertained, the wafer tests of different probe materials are stimulated under different OverDriver circumstances to calculate its stress and fatigue life. The results indicate that the greatest stress measured during the wafer test of the tungsten, SUS304 stainless steel, SUS316L stainless steel and SKD11 tool steel cantilever probe are all smaller than the yield strength, and the fatigue life could reach over one hundred K cycles. When catalogued by the cantilever probe fatigue life during one hundred K cycles, the life span, in order, is tungsten < SUS316L stainless steel < SUS304 stainless steel < SKD11 tool steel.

8. Enhanced Prediction of Gear Tooth Surface Fatigue Life Project

Data.gov (United States)

National Aeronautics and Space Administration — Sentient will develop an enhanced prediction of gear tooth surface fatigue life with rigorous analysis of the tribological phenomena that contribute to pitting...

9. FATIGUE LIFE PREDICTION THEORY OF COMPOSITE LAMINATES AND EXPERIMENTAL VERIFICATION

Institute of Scientific and Technical Information of China (English)

2003-01-01

According to traditional phenomenological fatigue methodology and modern continuum damage mechanics theory, dual fatigue cumulative damage rules to predict fatigue damage formation and propagation lives of the notched composite laminates are presented.A 3-dimensional damage constitutive equation of anisotropic composites is also established.Damage strain energy release rate is interpreted as a driving force of the fatigue delamination damage propagation.A new damage evolution equation and a damage propagation (a-(m-N( surface (stress amplitude-mean stress-life surface) are derived.Hence, using the method above, the fatigue life of composite components can be predicted.Finally, theoretically predicted results are compared with experimental data.It is found that the deviation of theoretic prediction from experimental results is about 22%.

10. GENERALIZED FATIGUE CONSTANT LIFE CURVE AND TWO-DIMENSIONAL PROBABILITY DISTRIBUTION OF FATIGUE LIMIT

Institute of Scientific and Technical Information of China (English)

熊峻江; 武哲; 高镇同

2002-01-01

According to the traditional fatigue constant life curve, the concept and the universal expression of the generalized fatigue constant life curve were proposed.Then, on the basis of the optimization method of the correlation coefficient, the parameter estimation formulas were induced and the generalized fatigue constant life curve with the reliability level p was given.From P-Sa-Sm curve, the two-dimensional probability distribution of the fatigue limit was derived.After then, three set of tests of LY11 CZ corresponding to the different average stress were carried out in terms of the two-dimensional up-down method.Finally, the methods are used to analyze the test results, and it is found that the analyzedresults with the high precision may be obtained.

11. FATIGUE LIFE EVALUATION OF SUSPENSION KNUCKLE USING MULTIBODY SIMULATION TECHNIQUE

Directory of Open Access Journals (Sweden)

A.G.A. Rahman

2012-12-01

Full Text Available Suspension is part of automotive systems, providing both vehicle control and passenger comfort. The knuckle is an important part within the suspension system, constantly encountering the cyclic loads subjecting it to fatigue failure. This paper presents an evaluation of the fatigue characteristics of a knuckle using multibody simulation (MBS techniques. Load time history extracted from the MBS is used for stress analysis. An actual road profile of road bumps was used as the input to MBS. The stress fluctuations for fatigue simulations are considered with the road profile. The strain-life method is utilized to assess the fatigue life. The instantaneous stress distributions and maximum principal stress are used for fatigue life predictions. Mesh sensitivity analysis has been performed. The results show that the steering link in the knuckle is found to be the most susceptible region for fatigue failure. The number of times the knuckle can manage a road bump at 40 km/hr is determined to be approximately 371 times with a 50% certainty of survival. The proposed method of using the loading time history extracted from MBS simulation for fatigue life estimation is found to be very promising for the accurate evaluation of the performance of suspension system components.

12. APPLICATION OF MULTIBODY SIMULATION FOR FATIGUE LIFE ESTIMATION

Directory of Open Access Journals (Sweden)

M. Kamal

2013-06-01

Full Text Available In automobile design, the safety of passengers is of prime concern to the manufacturers. Suspension is one of the safety-related automotive systems which is responsible for maintaining traction between the road and tires, and offers a comfortable ride experience to the passengers by absorbing disturbances. One of the critical components of the suspension system is the knuckle, which constantly faces cyclic loads subjecting it to fatigue failure. This paper presents an evaluation of the fatigue characteristics of a knuckle using a gravel road profile acquired using a data acquisition system and standard SAE profiles for the suspension (SAESUS, bracket (SAEBRAKT and transmission (SAETRN. The gravel road profile was applied as the input to a multi body simulation (MBS, and the load history for various mounting points of the knuckle is extracted. Fatigue life is predicted using the strain-life method. The instantaneous stress distributions and maximum principal stress are used for fatigue life predictions. From the results, the strut connection is found to be the critical region for fatigue failure. The fatigue life from loading extracted from gravel road MBS agreed well with the life prediction when standard SAE profiles were used. This close agreement shows the effectiveness of the load extraction technique from MBS. This method can also be effectively used for more complex loading conditions that occur during real driving environments.

13. A comparison of fatigue life prediction methodologies for rotorcraft

Science.gov (United States)

Everett, R. A., Jr.

1990-01-01

Because of the current U.S. Army requirement that all new rotorcraft be designed to a 'six nines' reliability on fatigue life, this study was undertaken to assess the accuracy of the current safe life philosophy using the nominal stress Palmgrem-Miner linear cumulative damage rule to predict the fatigue life of rotorcraft dynamic components. It has been shown that this methodology can predict fatigue lives that differ from test lives by more than two orders of magnitude. A further objective of this work was to compare the accuracy of this methodology to another safe life method called the local strain approach as well as to a method which predicts fatigue life based solely on crack growth data. Spectrum fatigue tests were run on notched (k(sub t) = 3.2) specimens made of 4340 steel using the Felix/28 tests fairly well, being slightly on the unconservative side of the test data. The crack growth method, which is based on 'small crack' crack growth data and a crack-closure model, also predicted the fatigue lives very well with the predicted lives being slightly longer that the mean test lives but within the experimental scatter band. The crack growth model was also able to predict the change in test lives produced by the rainflow reconstructed spectra.

14. Dramatic increase in fatigue life in hierarchical graphene composites.

Science.gov (United States)

Yavari, F; Rafiee, M A; Rafiee, J; Yu, Z-Z; Koratkar, N

2010-10-01

We report the synthesis and fatigue characterization of fiberglass/epoxy composites with various weight fractions of graphene platelets infiltrated into the epoxy resin as well as directly spray-coated on to the glass microfibers. Remarkably only ∼0.2% (with respect to the epoxy resin weight and ∼0.02% with respect to the entire laminate weight) of graphene additives enhanced the fatigue life of the composite in the flexural bending mode by up to 1200-fold. By contrast, under uniaxial tensile fatigue conditions, the graphene fillers resulted in ∼3-5-fold increase in fatigue life. The fatigue life increase (in the flexural bending mode) with graphene additives was ∼1-2 orders of magnitude superior to those obtained using carbon nanotubes. In situ ultrasound analysis of the nanocomposite during the cyclic fatigue test suggests that the graphene network toughens the fiberglass/epoxy-matrix interface and prevents the delamination/buckling of the glass microfibers under compressive stress. Such fatigue-resistant hierarchical materials show potential to improve the safety, reliability, and cost effectiveness of fiber-reinforced composites that are increasingly the material of choice in the aerospace, automotive, marine, sports, biomedical, and wind energy industries.

15. Life prediction of thermal-mechanical fatigue using strainrange partitioning

Science.gov (United States)

Halford, G. R.; Manson, S. S.

1975-01-01

This paper describes the applicability of the method of Strainrange Partitioning to the life prediction of thermal-mechanical strain-cycling fatigue. An in-phase test on 316 stainless steel is analyzed as an illustrative example. The observed life is in excellent agreement with the life predicted by the method using the recently proposed Step-Stress Method of experimental partitioning, the Interaction Damage Rule, and the life relationships determined at an isothermal temperature of 705 C. Implications of the present study are discussed relative to the general thermal fatigue problem.

16. a Study on the Fretting Fatigue Life of Zircaloy Alloys

Science.gov (United States)

Kwon, Jae-Do; Park, Dae-Kyu; Woo, Seung-Wan; Chai, Young-Suck

Studies on the strength and fatigue life of machines and structures have been conducted in accordance with the development of modern industries. In particular, fine and repetitive cyclic damage occurring in contact regions has been known to have an impact on fretting fatigue fractures. The main component of zircaloy alloy is Zr, and it possesses good mechanical characteristics at high temperatures. This alloy is used in the fuel rod material of nuclear power plants because of its excellent resistance. In this paper, the effect of the fretting damage on the fatigue behavior of the zircaloy alloy is studied. Further, various types of mechanical tests such as tension and plain fatigue tests are performed. Fretting fatigue tests are performed with a flat-flat contact configuration using a bridge-type contact pad and plate-type specimen. Through these experiments, it is found that the fretting fatigue strength decreases by about 80% as compared to the plain fatigue strength. Oblique cracks are observed in the initial stage of the fretting fatigue, in which damaged areas are found. These results can be used as the basic data for the structural integrity evaluation of corrosion-resisting alloys considering the fretting damages.

17. Rolling contact fatigue life of ion-implanted GCr15

Institute of Scientific and Technical Information of China (English)

2000-01-01

Presents an experimental research into the rooling contact fatigue life of GCr15 steel with Tix N, TiX N + Ag and Tix N + DLC layers ion-implanted using the plasma ion-implantation technology on a ball-rod style high-speed con tact fatigue tester, and concludes with test results that the fatigue life increases to varying degrees with Tix N, Tix N + Ag, and Tix N + DLC layers implanted, and increases 1.8 times with Tix N + Ag layer implanted, hairline cracks grow continuously into fatigue pits under the action of shear stress in the superficial layer of material, and ion-implantation acts to prevent initiation of cracks and slow down propagation of cracks.

18. A methodology to evaluate the fatigue life of flexible pipes

Energy Technology Data Exchange (ETDEWEB)

Sousa, Fernando J.M. de; Sousa, Jose Renato M. de; Siqueira, Marcos Q. de; Sagrilo, Luis V.S. [Coordenacao dos Programas de Pos-graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil); Lemos, Carlos Alberto D. de [Petroleo Brasileiro S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil)

2009-07-01

This paper focus on a methodology to perform the fatigue analysis of flexible pipes. This methodology employs functions that convert forces and moments obtained in global analyses into stresses. The stresses are then processed by well-known cycle counting methods, and S-N curves evaluate the damage at several points in the pipe cross-section. Palmgren-Miner linear damage hypothesis is assumed in order to calculate the accumulated fatigue damage. A parametric study on the fatigue life of a flexible pipe employing this methodology is presented. The main points addressed in the study are the influence of friction between layers in the results, the importance of evaluating the fatigue life in various points of the pipe cross-section and the effect of different mean stress levels. The obtained results suggest that the consideration of friction effects strongly influences the fatigue life of flexible risers and these effects have to be accounted both in the global and local analyses of the riser. Moreover, mean stress effects are also significant and at least 8 equally spaced wires in each analyzed section of the riser must be considered in fatigue analyses. (author)

19. A criterion for high-cycle fatigue life and fatigue limit prediction in biaxial loading conditions

Institute of Scientific and Technical Information of China (English)

ukasz Pejkowski; Dariusz Skibicki

2016-01-01

This paper presents a criterion for high-cycle fatigue life and fatigue strength estimation under periodic proportional and non-proportional cyclic loading. The cri-terion is based on the mean and maximum values of the second invariant of the stress deviator. Important elements of the criterion are: function of the non-proportionality of fatigue loading and the materials parameter that expresses the materials sensitivity to non-proportional loading. The methods for the materials parameters determination uses three S–N curves: tension–compression, torsion, and any non-proportional loading proposed. The criterion has been verified using experimental data, and the results are included in the paper. These results should be considered as promis-ing. The paper also includes a proposal for multiaxial fatigue models classification due to the approach for the non-proportionality of loading.

20. STUDY ON FATIGUE SHORT CRACK GROWTH LAW AND FATIGUE LIFE FOR MEDIUM CARBON STEELS

Institute of Scientific and Technical Information of China (English)

1998-01-01

The fatigue crack initiation from notch root and the short-crack growth laws of two medium carbon alloying structural steels-35CrMo and 42CrMo are investigated under the different stress ratios R=0.1, 0.3) and three-point bending condition. The relationships between the maximum stress range at the notch root Δσmax and the number of cycles before fatigue crack initiation Ni are determined. The threshold stresses of fatigue crack initiation (Δσmax)th are got, and the smallcrack growth laws are obtained for these steels. An effective and convenient method is proposed for predicting the fatigue life of the notch specimens.

1. On Fatigue Life Under Stationary Gaussian Random Loads (A)

DEFF Research Database (Denmark)

Talreja, R.

1973-01-01

Power spectra are taken to represent stationary Gaussian random loads. Location, scale, and shape parameters are defined for power spectra and proposed as a convenient set of load parameters for random loads. The center frequency of a power spectrum, defined as its weighted average frequency......, is proposed as a measure of fatigue life. A servohydraulic closed loop testing machine is used to load specimens of carbon steel under six different power spectral shapes. Test results are utilized to evaluate a fatigue life function formulated in terms of the load parameters. The concept of a shape operator...

2. Fatigue life prediction of crankshaft repaired by twin arc spraying

Institute of Scientific and Technical Information of China (English)

ZHANG Guo-qing; WANG Cheng-tao; PU Geng-qiang

2005-01-01

This paper used Baumel Jr. and Seeger's approach estimating fatigue parameters of 48MnV with 3Cr13coatings. The fatigue life of the crankshaft of a six-cylinder engine, repaired by twin arc spraying 3cr13 deposits, is respectively calculated using different damage model such as S-N method, normal strain approaches, SWT-Bannantine approaches, shear strain approaches, and fatemi-Socie method based on dynamical simulation and FE analysis of crankshaft. The results indicate that the traditional calculation is conservative and that the life of crankshaft repaired by arc spraying is sufficient.

3. Fatigue in high-speed aluminium craft: A design methodology for predicting the fatigue life

NARCIS (Netherlands)

Tuitman, J.T.; Hoogendoorn, D.

2013-01-01

Within the VOMAS project, a methodology has been developed to predict the fatigue life of high-speed aluminium crafts. This paper describes this methodology and its implementation into a computational tool. This methodology computes the seakeeping and resulting pressure at the structure for all cond

4. Fatigue life of ablation-cast 6061-T6 components

Energy Technology Data Exchange (ETDEWEB)

Tiryakioglu, Murat, E-mail: m.tiryakioglu@unf.edu [School of Engineering. University of North Florida, Jacksonville, FL 32224 (United States); Eason, Paul D. [School of Engineering. University of North Florida, Jacksonville, FL 32224 (United States); Campbell, John [Department of Metallurgy and Materials, University of Birmingham, Edgbaston B15 2TT (United Kingdom)

2013-01-01

The fatigue life of 6061-T6 alloy, normally used in its wrought form, was investigated in this study in cast form from parts produced by the new ablation casting process. All specimens were excised from military castings. Unidirectional tensile test results yielded elongation values comparable to forgings and extrusions. A total of 39 fatigue specimens were tested by the rotating cantilever beam technique at five maximum stress levels. Moreover nine specimens excised from a forging were also tested for comparison. Results revealed that the fatigue life of ablation-cast 6061-T6 (i) follows a three-parameter Weibull distribution, and (ii) is comparable to data from the 6061 forging and is superior to conventionally cast Al-7% Si-Mg alloy castings published in the literature. Analysis of the fracture surfaces of ablation-cast 6061-T6 via scanning electron microscopy showed the existence of fracture surface facets and multiple cracks propagating in different directions.

5. Effect of adjusting pulse durations of functional electrical stimulation cycling on energy expenditure and fatigue after spinal cord injury

Directory of Open Access Journals (Sweden)

Ashraf S. Gorgey, MPT, PhD, FACSM

2015-02-01

Full Text Available The purpose of the current study was to determine the effects of three different pulse durations (200, 350, and 500 microseconds [P200, P350, and P500, respectively] on oxygen uptake, cycling performance, and energy expenditure (EE percentage of fatigue of the knee extensor muscle group immediately and 48 to 72 h after cycling in persons with spinal cord injury (SCI. A convenience sample of 10 individuals with motor complete SCI participated in a repeated-measures design using a functional electrical stimulation (FES cycle ergometer over a 3 wk period. There was no difference among the three FES protocols on relative oxygen uptake or cycling EE. Delta EE between exercise and rest was 42% greater in both P500 and P350 than in P200 (p = 0.07, whereas recovery oxygen uptake was 23% greater in P350 than in P200 (p = 0.03. There was no difference in the outcomes of the three pulse durations on muscle fatigue. Knee extensor torque significantly decreased immediately after (p < 0.001 and 48 to 72 h after (p < 0.001 FES leg cycling. Lengthening pulse duration did not affect submaximal or relative oxygen uptake or EE, total EE, and time to fatigue. Greater recovery oxygen updake and delta EE were noted in P350 and P500 compared with P200. An acute bout of FES leg cycling resulted in torque reduction that did not fully recover 48 to 72 h after cycling.

6. Fatigue Life Assessment of Selected Engineering Materials Based on Modified Low-Cycle Fatigue Test

Directory of Open Access Journals (Sweden)

M. Maj

2013-01-01

Full Text Available In this study, the mechanical tests were carried out on ductile iron of EN-GJS-600-3 grade and on grey cast iron of EN-GJL-250 grade.The fatigue life was evaluated in a modified low-cycle fatigue test (MLCF, which enables the determination of parameters resulting fromthe Manson-Coffin-Morrow relationship.The qualitative and quantitative metallographic studies conducted by light microscopy on selected samples of ductile iron with spheroidalgraphite and grey cast iron with lamellar graphite (showing only small variations in mechanical properties, confirmed also smallvariations in the geometrical parameters of graphite related with its content and morphological features.

7. Relationship between fatigue life in the creep-fatigue region and stress-strain response

Science.gov (United States)

1988-01-01

On the basis of mechanical tests and metallographic studies, strainrange partitioned lives were predicted by introducing stress-strain materials parameters into the Universal Slopes Equation. This was the result of correlating fatigue damage mechanisms and deformation mechanisms operating at elevated temperatures on the basis of observed mechanical and microstructural behavior. Correlation between high temperature fatigue and stress strain properties for nickel base superalloys and stainless steel substantiated the method. Parameters which must be evaluated for PP- and CC- life are the maximum stress achievable under entirely plastic and creep conditions respectively and corresponding inelastic strains, and the two more pairs of stress strain parameters must be ascertained.

8. Multi-Axial Damage Index and Accumulation Model for Predicting Fatigue Life of CMC Materials Project

Data.gov (United States)

National Aeronautics and Space Administration — The fatigue life of CMCs must be well characterized for the safe and reliable use of these materials as integrated TPS components. Existing fatigue life prediction...

9. Survey on damage mechanics models for fatigue life prediction

NARCIS (Netherlands)

Silitonga, S.; Maljaars, J.; Soetens, F.; Snijder, H.H.

2013-01-01

Engineering methods to predict the fatigue life of structures have been available since the beginning of the 20th century. However, a practical problem arises from complex loading conditions and a significant concern is the accuracy of the methods under variable amplitude loading. This paper provide

10. Fatigue Life Analysis of Rolling Bearings Based on Quasistatic Modeling

Directory of Open Access Journals (Sweden)

Wei Guo

2015-01-01

Full Text Available Rolling bearings are widely used in aeroengine, machine tool spindles, locomotive wheelset, and so forth. Rolling bearings are usually the weakest components that influence the remaining life of the whole machine. In this paper, a fatigue life prediction method is proposed based on quasistatic modeling of rolling bearings. With consideration of radial centrifugal expansion and thermal deformations on the geometric displacement in the bearings, the Jones’ bearing model is updated, which can predict the contact angle, deformation, and load between rolling elements and bearing raceways more accurately. Based on Hertz contact theory and contact mechanics, the contact stress field between rolling elements and raceways is calculated. A coupling model of fatigue life and damage for rolling bearings is given and verified through accelerated life test. Afterwards, the variation of bearing life is investigated under different working conditions, that is, axial load, radial load, and rotational speed. The results suggested that the working condition had a great influence on fatigue life of bearing parts and the order in which the damage appears on bearing parts.

11. Fatigue in cold-forging dies: Tool life analysis

DEFF Research Database (Denmark)

Skov-Hansen, P.; Bay, Niels; Grønbæk, J.;

1999-01-01

In the present investigation it is shown how the tool life of heavily loaded cold-forging dies can be predicted. Low-cycle fatigue and fatigue crack growth testing of the tool materials are used in combination with finite element modelling to obtain predictions of tool lives. In the models...... the number of forming cycles is calculated first to crack initiation and then during crack growth to fatal failure. An investigation of a critical die insert in an industrial cold-forging tool as regards the influence of notch radius, the amount and method of pre-stressing and the selected tool material...

12. Fatigue Life of Postbuckled Structures with Indentation Damages

Science.gov (United States)

Davila, Carlos G.; Bisagni, Chiara

2016-01-01

The fatigue life of composite stiffened panels with indentation damage was investigated experimentally using single stringer compression specimens. Indentation damage was induced on one of the two flanges of each stringer. The experiments were conducted using advanced instrumentation, including digital image correlation, passive thermography, and in-situ ultrasonic scanning. Specimens with initial indentation damage lengths of 32 millimeters to 56 millimeters were tested quasi-statically and in fatigue, and the effects of cyclic load amplitude and damage size were studied. A means of comparison of the damage propagation rates and collapse loads based on a stress intensity measure and the Paris law is proposed.

13. Fatigue Life of Postbuckled Structures with Indentation Damage

Science.gov (United States)

Davila, Carlos G.; Bisagni, Chiara

2016-01-01

The fatigue life of composite stiffened panels with indentation damage was investigated experimentally using single stringer compression specimens. Indentation damage was induced on one of the two flanges of the stringer. The experiments were conducted using advanced instrumentation, including digital image correlation, passive thermography, and in-situ ultrasonic scanning. Specimens with initial indentation damage lengths of 37 millimeters to 56 millimeters were tested in fatigue and the effects of cyclic load amplitude and damage size were studied. A means of comparison of the damage propagation rates and collapse loads based on a stress intensity measure and the Paris law is proposed.

14. Blade Group Fatigue Life Calculation under Resonant Stresses

Directory of Open Access Journals (Sweden)

Zlatko Petreski

2017-02-01

Full Text Available The results of the simulations of the blade group resonant stresses in a FE environment and fatigue life calculation are presented in this paper. Numerical calculation for determination of natural frequencies, mode shapes and dynamic stresses, based on FEM and NISA package is used. Analyses are made on the blade group with three blades with rectangular cross section and typical turbine blades with taper, pretwist and asymmetric airfoil as well. The influence of the position of the lacing wire on the resonant stresses is analyzed. Three-dimensional finite element models of the blade group are made by using twenty node isoparametric solid elements. The number of degrees of freedom is different for each model (more than 30000 DOF. The fatigue life and consequent life prediction according the stress load history of the blades is made. The results of the investigation are given in tables and graphics.

15. A State-of-the-Art Review on Fatigue Life Assessment of Steel Bridges

Directory of Open Access Journals (Sweden)

X. W. Ye

2014-01-01

Full Text Available Fatigue is among the most critical forms of damage potentially occurring in steel bridges, while accurate assessment or prediction of the fatigue damage status as well as the remaining fatigue life of steel bridges is still a challenging and unsolved issue. There have been numerous investigations on the fatigue damage evaluation and life prediction of steel bridges by use of deterministic or probabilistic methods. The purpose of this review is devoted to presenting a summary on the development history and current status of fatigue condition assessment of steel bridges, containing basic aspects of fatigue, classical fatigue analysis methods, data-driven fatigue life assessment, and reliability-based fatigue condition assessment.

16. The Study on Fatigue Experiment and Reliability Life of Submarine Pipeline Steel

OpenAIRE

Yan Yifei; Shao Bing; Liu Jinkun; Cheng Lufeng

2013-01-01

The aim of the fatigue experiment study is to solve the fatigue fracture problem of X70 submarine tubing when it is under the scouring effect of offshore current. The multilevel fatigue experiments are carried out following the internation (GB4337-84) recommended method. The standard round bar fatigue specimen was made by the material of submarine pipeline steel. The fatigue life of submarine pipeline steel in different survival probability and P-S-N curve were achieved. According to reliabil...

17. A Sensitivity Analysis on Component Reliability from Fatigue Life Computations

Science.gov (United States)

1992-02-01

AD-A247 430 MTL TR 92-5 AD A SENSITIVITY ANALYSIS ON COMPONENT RELIABILITY FROM FATIGUE LIFE COMPUTATIONS DONALD M. NEAL, WILLIAM T. MATTHEWS, MARK G...HAGI OR GHANI NUMBI:H(s) Donald M. Neal, William T. Matthews, Mark G. Vangel, and Trevor Rudalevige 9. PERFORMING ORGANIZATION NAME AND ADDRESS lU...Technical Information Center, Cameron Station, Building 5, 5010 Duke Street, Alexandria, VA 22304-6145 2 ATTN: DTIC-FDAC I MIAC/ CINDAS , Purdue

18. An Analytical Model for Fatigue Life Prediction Based on Fracture Mechanics and Crack Closure

DEFF Research Database (Denmark)

Ibsø, Jan Behrend; Agerskov, Henning

1996-01-01

Fatigue in steel structures subjected to stochastic loading is studied. Of special interest is the problem of fatigue damage accumulation and in this connection, a comparison between experimental results and results obtained using fracture mechanics. Fatigue test results obtained for welded plate...... test specimens are compared with fatigue life predictions using a fracture mechanics approach. In the calculation of the fatigue life, the influence of the welding residual stresses and crack closure on the fatigue crack growth is considered. A description of the crack closure model for analytical...... determination of the fatigue life is included. Furthermore, the results obtained in studies of the various parameters that have an influence on the fatigue life, are given. A very good agreement between experimental and analytical results is obtained, when the crack closure model is used in determination...

19. Fatigue Life Estimation of Medium-Carbon Steel with Different Surface Roughness

Directory of Open Access Journals (Sweden)

Changyou Li

2017-03-01

Full Text Available Medium-carbon steel is commonly used for the rail, wire ropes, tire cord, cold heading, forging steels, cold finished steel bars, machinable steel and so on. Its fatigue behavior analysis and fatigue life estimation play an important role in the machinery industry. In this paper, the estimation of fatigue life of medium-carbon steel with different surface roughness using established S-N and P-S-N curves is presented. To estimate the fatigue life, the effect of the average surface roughness on the fatigue life of medium-carbon steel has been investigated using 75 fatigue tests in three groups with average surface roughness (Ra: 0.4 μm, 0.8 μm, and 1.6 μm, respectively. S-N curves and P-S-N curves have been established based on the fatigue tests. The fatigue life of medium-carbon steel is then estimated based on Tanaka-Mura crack initiation life model, the crack propagation life model using Paris law, and material constants of the S-N curves. Six more fatigue tests have been conducted to validate the presented fatigue life estimation formulation. The experimental results have shown that the presented model could estimate well the mean fatigue life of medium-carbon steel with different surface roughness.

20. A Modified Fatigue Damage Model for High-Cycle Fatigue Life Prediction

Directory of Open Access Journals (Sweden)

Meng Wang

2016-01-01

Full Text Available Based on the assumption of quasibrittle failure under high-cycle fatigue for the metal material, the damage constitutive equation and the modified damage evolution equation are obtained with continuum damage mechanics. Then, finite element method (FEM is used to describe the failure process of metal material. The increment of specimen’s life and damage state can be researched using damage mechanics-FEM. Finally, the lifetime of the specimen is got at the given stress level. The damage mechanics-FEM is inserted into ABAQUS with subroutine USDFLD and the Python language is used to simulate the fatigue process of titanium alloy specimens. The simulation results have a good agreement with the testing results under constant amplitude loading, which proves the accuracy of the method.

1. An Analytical Model for Fatigue Life Prediction Based on Fracture Mechanics and Crack Closure

DEFF Research Database (Denmark)

Ibsø, Jan Behrend; Agerskov, Henning

1996-01-01

Fatigue in steel structures subjected to stochastic loading is studied. Of special interest is the problem of fatigue damage accumulation and in this connection, a comparison between experimental results and results obtained using fracture mechanics. Fatigue test results obtained for welded plate...... test specimens are compared with fatigue life predictions using a fracture mechanics approach. In the calculation of the fatigue life, the influence of the welding residual stresses and crack closure on the fatigue crack growth is considered. A description of the crack closure model for analytical...... of the analytical fatigue lives. Both the analytical and experimental results obtained show that the Miner rule may give quite unconservative predictions of the fatigue life for the types of stochastic loading studied....

2. The Effect of Structural Quality on Fatigue Life in 319 Aluminum Alloy Castings

Science.gov (United States)

Özdeş, Hüseyin; Tiryakioğlu, Murat

2016-12-01

Tensile and fatigue life data for 319 aluminum alloy from seventeen datasets reported in four independent studies from the literature have been reanalyzed. Analysis of fatigue life data involved mean stress correction for different R ratios used in fatigue testing, inclusion of survival (runout) data along with failure data, as well as volumetric correction for Weibull distributions for different specimen sizes used in these studies. Tensile data have been transformed into the structural quality index, Q T, which is used as a measure of the structural quality of castings. A distinct relationship has been observed between the expected fatigue life and mean quality index. Moreover, fatigue strengths at 104 and 106 cycles have been found increase with quality index, providing further evidence about the relationship observed between structural quality and fatigue performance. Empirical equations between Basquin parameters and structural quality index have been developed. The use of the comprehensive methodology to estimate fatigue life is demonstrated with an example.

3. The Effect of Structural Quality on Fatigue Life in 319 Aluminum Alloy Castings

Science.gov (United States)

Özdeş, Hüseyin; Tiryakioğlu, Murat

2017-02-01

Tensile and fatigue life data for 319 aluminum alloy from seventeen datasets reported in four independent studies from the literature have been reanalyzed. Analysis of fatigue life data involved mean stress correction for different R ratios used in fatigue testing, inclusion of survival (runout) data along with failure data, as well as volumetric correction for Weibull distributions for different specimen sizes used in these studies. Tensile data have been transformed into the structural quality index, Q T, which is used as a measure of the structural quality of castings. A distinct relationship has been observed between the expected fatigue life and mean quality index. Moreover, fatigue strengths at 104 and 106 cycles have been found increase with quality index, providing further evidence about the relationship observed between structural quality and fatigue performance. Empirical equations between Basquin parameters and structural quality index have been developed. The use of the comprehensive methodology to estimate fatigue life is demonstrated with an example.

4. Evaluation of corrosion fatigue and life prediction of lower arm for automotive suspension component

Science.gov (United States)

Kim, Yong-Sang; Kim, Jung-Gu

2017-01-01

Lower arm is one of the suspension components of automobile. It is suffered from driving vibration and corrosive environment, namely corrosion fatigue. In this study, corrosion fatigue property of lower arm was investigated, and a modified model based on Palmgren-Miner rule was developed to predict the lifetimes of corrosion fatigue. The corrosion fatigue life of lower arm was about 1/6 times shorter than fatigue life. Based on the results of corrosion fatigue tests and meteorological data in Seoul and Halifax, the corrosion fatigue life of lower arm was predicted. The satisfaction of 10-year and 300,000 km warranty was dominated by the climate of automobile driving. This prediction indicates that the weather condition or driving condition influences the life of automotive parts. Therefore, to determine the warranty of automotive parts, the driving condition has to be carefully considered.

5. Study on effect of mean stress on fatigue life prediction of thin film structure

Energy Technology Data Exchange (ETDEWEB)

Shin, Myung Soo [Ahtti Co., Seongnam (Korea, Republic of); Park, Jun Hyu [Tongmyong University, Busan (Korea, Republic of); Kim, Jung Yup [Korea Institute of Machinery and Materials, Daejeon (Korea, Republic of)

2016-04-15

This paper describes the effect of mean stress on fatigue life prediction of structure made with thin film. It is well known that the mean stress influences fatigue life prediction of mechanical structure. We investigated a reasonable method for considering mean stress when fatigue strength assessment of micro structure of thin film should be performed. Fatigue tests of smooth specimen of beryllium-copper (BeCu) thin film were performed in ambient air at R = 0.1 with 5 Hz. A micro probe was designed and made with BeCu thin film by the precision press process. Fatigue tests of micro structure were performed with 5 Hz frequency, in ambient air to verify the fatigue life predicted by computer simulation through FE analysis. The fatigue life predicted by the Sa -N curve modified by Goodman method with principal stress through FE analysis shows a more reasonable result than other methods.

6. Development of a Generic Creep-Fatigue Life Prediction Model

Science.gov (United States)

Goswami, Tarun

2002-01-01

The objective of this research proposal is to further compile creep-fatigue data of steel alloys and superalloys used in military aircraft engines and/or rocket engines and to develop a statistical multivariate equation. The newly derived model will be a probabilistic fit to all the data compiled from various sources. Attempts will be made to procure the creep-fatigue data from NASA Glenn Research Center and other sources to further develop life prediction models for specific alloy groups. In a previous effort [1-3], a bank of creep-fatigue data has been compiled and tabulated under a range of known test parameters. These test parameters are called independent variables, namely; total strain range, strain rate, hold time, and temperature. The present research attempts to use these variables to develop a multivariate equation, which will be a probabilistic equation fitting a large database. The data predicted by the new model will be analyzed using the normal distribution fits, the closer the predicted lives are with the experimental lives (normal line 1 to 1 fit) the better the prediction. This will be evaluated in terms of a coefficient of correlation, R 2 as well. A multivariate equation developed earlier [3] has the following form, where S, R, T, and H have specific meaning discussed later.

7. In-situ fatigue life prognosis for composite laminates based on stiffness degradation

Data.gov (United States)

National Aeronautics and Space Administration — In this paper, a real-time composite fatigue life prognosis framework is proposed. The proposed methodology combines Bayesian inference, piezoelectric sensor...

8. Statistical Distribution of Fatigue Life for Cast TiAl Alloy

Directory of Open Access Journals (Sweden)

WAN Wenjuan

2016-08-01

Full Text Available Statistic distribution of fatigue life data and its controls of cast Ti-47.5Al-2.5V-1.0Cr-0.2Zr (atom fraction/% alloy were investigated. Fatigue tests were operated by means of load-controlled rotating bending fatigue tests (R=-1 performed at a frequency of 100 Hz at 750 ℃ in air. The fracture mechanism was analyzed by observing the fracture surface morphologies through scanning electron microscope,and the achieved fatigue life data were analyzed by Weibull statistics. The results show that the fatigue life data present a remarkable scatter ranging from 103 to 106 cycles, and distribute mainly in short and long life regime. The reason for this phenomenon is that the fatigue crack initiators are different with different specimens. The crack initiators for short-life specimens are caused by shrinkage porosity, and for long-life ones are caused by bridged porosity interface and soft-oriented lamellar interface. Based on the observation results of fracture surface, two-parameter Weibull distribution model for fatigue life data can be used for the prediction of fatigue life at a certain failure probability. It has also shown that the shrinkage porosity causes the most detrimental effect to fatigue life.

9. The Study on Fatigue Experiment and Reliability Life of Submarine Pipeline Steel

Directory of Open Access Journals (Sweden)

Yan Yifei

2013-02-01

Full Text Available The aim of the fatigue experiment study is to solve the fatigue fracture problem of X70 submarine tubing when it is under the scouring effect of offshore current. The multilevel fatigue experiments are carried out following the internation (GB4337-84 recommended method. The standard round bar fatigue specimen was made by the material of submarine pipeline steel. The fatigue life of submarine pipeline steel in different survival probability and P-S-N curve were achieved. According to reliability numerical analysis method, the reliability fatigue life of pipeline steel in different stress level is got. The results show that the fatigue life of X70 submarine pipeline steel obeys the normal distribution. The detection of submarine pipeline scouring condation should be enhanced and the pipeline zone which was scoured seriously should be repaired and controlled effectively in order to reduce the scouring effect of ocean current.

10. Structural health monitoring of wind towers: residual fatigue life estimation

Science.gov (United States)

Benedetti, M.; Fontanari, V.; Battisti, L.

2013-04-01

In a recent paper (Benedetti et al 2011 Smart Mater. Struct. 20 055009), the authors investigated the possibility of detecting cracks in critical sites of onshore wind towers using a radial arrangement of strain sensors around the tower periphery in the vicinity of the base welded joint. Specifically, the strain difference between adjacent strain sensors is used as a damage indicator. The number of sensors to be installed is determined by the minimum crack size to be detected, which in turn depends on the expected extreme wind conditions and programmed inspection/repair schedule. In this companion paper, we address these issues by investigating possible strategies for residual fatigue life assessment and management of onshore wind towers once the crack has been detected. For this purpose, fracture mechanics tests are carried out using welded samples to quantify the resistance to fatigue crack growth as well as the elastic-plastic fracture toughness of the welded joint at the tower base. These material strength characteristics are used to estimate (i) the critical crack size for structural integrity on the basis of fracture toughness tests, elastoplastic finite element analyses and loading spectra under extreme wind conditions, (ii) the residual life before structural collapse, applying a frequency-domain method to typical in-service wind actions and wind directionality.

11. Fatigue life of organic fiber/epoxy pressure vessels

Science.gov (United States)

Hamstad, M. A.; Chiao, T. T.; Patterson, R. G.

1975-01-01

The cyclic fatigue life of 10.2-cm-diam cylindrical pressure vessels has been studied. The vessels were made of an organic fiber/epoxy composite. To determine the typical strength distribution of the vessels, 25 of them were internally pressurized until they burst. Twenty-five vessels were then tested under sinusoidal cycling at 1 Hz between 4% and 91% of the mean burst strength. An additional twenty-five vessels were tested between 4% and 91% with a rectangular pressure pulse at 1/3 Hz. A limited number of vessels were tested for stress rupture at the 91% level. Cyclic life was found to depend on time at peak load as well as the number of stress cycles.

12. A Model of the Fatigue Life Distribution of Composite Laminates Based on Their Static Strength Distribution

Institute of Scientific and Technical Information of China (English)

Wu Fuqiang; Yao Weixing

2008-01-01

The reasons of the static strength dispersion and the fatigue life dispersion of composite laminates are analyzed in this article.It is concluded that the inner original defects,which derived from the manufacturing process of composite laminates,are the common and major reason of causing the random distributions of the static strength and the fatigue life.And there is a correlative relation between the two distributions.With the study of statistical relationship between the fatigue loading and the fatigue life in the uniform confidence level and the same survival rate S-N curves of material,the relationship between the static strength distribution and the fatigue life distribution through a material S-N curve model has been obtained.And then the model which is used to describe the distributions of fatigue life of composites,based on their distributions of static strength,is set up.This model reasonably reflects the effects of the inner original defects on the static strength dispersion and on the fatigue life dispersion of composite laminates.The experimental data of three kinds of composite laminates are employed to verify this model,and the results show that this model can predict the random distributions of fatigue life for composites under any fatigue loads fairly well.

13. Prediction of Fatigue Life of a Continuous Bridge Girder Based on Vehicle Induced Stress History

Directory of Open Access Journals (Sweden)

V.G. Rao

2003-01-01

Full Text Available The fatigue damage assessment of bridge components by conducting a full scale fatigue testing is often prohibitive. A need, therefore, exists to estimate the fatigue damage in bridge components by a simulation of bridge-vehicle interaction dynamics due to the action of the actual traffic. In the present paper, a systematic method has been outlined to find the fatigue damage in the continuous bridge girder based on stress range frequency histogram and fatigue strength parameters of the bridge materials. Vehicle induced time history of maximum flexural stresses has been obtained by Monte Carlo simulation process and utilized to develop the stress range frequency histogram taking into consideration of the annual traffic volume. The linear damage accumulation theory is then applied to calculate cumulative damage index and fatigue life of the bridge. Effect of the bridge span, pavement condition, increase of vehicle operating speed, weight and suspension characteristics on fatigue life of the bridge have been examined.

14. Fatigue life prediction and strength degradation of wind turbine rotor blade composites

NARCIS (Netherlands)

Nijssen, R.P.L.

2006-01-01

Wind turbine rotor blades are subjected to a large number of highly variable loads, but life predictions are typically based on constant amplitude fatigue behaviour. Therefore, it is important to determine how service life under variable amplitude fatigue can be estimated from constant amplitude fat

15. Effect of higher strain range cycling on near fatigue-limit fatigue life

Energy Technology Data Exchange (ETDEWEB)

Fukuoka, Chie; Nakagawa, Y.G. [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan). Research Inst; Rosinski, S.T.

1999-04-01

The objective of this study is to clarify the effects of pre-cycling above the fatigue limit on near the fatigue-limit fatigue behaviors of SA508, low alloy steel for nuclear pressure vessels, correlating fatigue lifetime with microstructural changes in the bulk. It has been observed that dislocation cell structure is well developed in an as-received SA508 sample and the misorientation among cells increases with fatigue accumulation during fatigue tests. The cell to cell misorientation was measured and statistically quantified by the Selected Area electron beam Diffraction (SAD). It was shown that a fatigue crack started growing abruptly when the SAD value (the mean misorientation among cells) exceeded a critical angle, 4-5 degrees. Fatigue tests were performed for SA508 samples, first at a high total strain range (0.62%) to 10, 100, and 6000 cycles followed by cycling at near the fatigue-limit strain range (0.40%). The sample with pre-cycling for 100 and 6000 cycles failed while ones with pre-cycling for 10 cycles and without pre-cycling did not rupture till about 10{sup 6} cycles where the tests were terminated. Small surface cracks were found all samples pre-cycled at the high strain range but the cracks were arrested for a long time at the near fatigue limit cycling followed by an abrupt growth at the failure. It was found by the SAD that samples failed at the fatigue limit when the average misorientation among cells exceeds the critical angle regardless of pre-cycling histories. The SAD value changed even during cycling below the fatigue limit, and the change in SAD value was strongly influenced by the number of pre-cycling above the fatigue limit. These changes well agreed with fatigue lifetime of the samples. (author)

16. The application of strain field intensity method in the steel bridge fatigue life evaluation

Science.gov (United States)

Zhao, Xuefeng; Wang, Yanhong; Cui, Yanjun; Cao, Kaisheng

2012-04-01

Asce's survey shows that 80%--90% bridge damage were associated with fatigue and fracture problems. With the operation of vehicle weight and traffic volume increases constantly, the fatigue of welded steel bridge is becoming more and more serious in recent years. A large number of studies show that most prone to fatigue damage of steel bridge is part of the welding position. Thus, it's important to find a more precise method to assess the fatigue life of steel bridge. Three kinds of fatigue analysis method is commonly used in engineering practice, such as nominal stress method, the local stress strain method and field intensity method. The first two methods frequently used for fatigue life assessment of steel bridge, but field intensity method uses less ,and it widely used in fatigue life assessment of aerospace and mechanical. Nominal stress method and the local stress strain method in engineering has been widely applied, but not considering stress gradient and multiaxial stress effects, the accuracy of calculation stability is relatively poor, so it's difficult to fully explain the fatigue damage mechanism. Therefore, it used strain field intensity method to evaluate the fatigue life of steel bridge. The fatigue life research of the steel bridge based on the strain field method and the fatigue life of the I-section plate girder was analyzed. Using Ansys on the elastoplastic finite element analysis determined the dangerous part of the structure and got the stress-strain history of the dangerous point. At the same time, in order to divide the unit more elaborate introduced the sub-structure technology. Finally, it applies K.N. Smith damage equation to calculate the fatigue life of the dangerous point. In order to better simulating the actual welding defects, it dug a small hole in the welding parts. It dug different holds from different view in the welding parts and plused the same load to calculate its fatigue life. Comparing the results found that the welding

17. Prediction of multiaxial fatigue life for notched specimens of titanium alloy TC4

Energy Technology Data Exchange (ETDEWEB)

Wu, Z. R.; Li, Z. X. [Southeast University, Nanjing (China); Hu, X. T.; Song, Y. D. [Nanjing University, Nanjing (China)

2016-05-15

Both the proportional and nonproportional multiaxial fatigue tests were conducted on two kinds of notched specimens of titanium alloy TC4. The multiaxial fatigue critical area of notched specimen is considered as the location experiencing the maximum damage. It is unsatisfactory to predict the multiaxial fatigue life with the local stress and strain in the fatigue critical area. The critical distance concepts are employed in the multiaxial life prediction method for notched specimens. The proposed method was checked by the test data of TC4 notched specimens. The prediction results are almost within a factor of three scatter band of the test results.

18. Study on Contact Fatigue Life and Failure Mechanism of Subquenched 42CrMo Steel

Institute of Scientific and Technical Information of China (English)

HE Bo-lin; YU Ying-xia; SHAO Er-yu

2004-01-01

The effect of undissolved ferrite amount in subcritically quenched 42CrMo steel on contact fatigue properties and failure mechanism were studied. The amount of undissolved ferrite in the steel were 0%,3%,10%,15% and 20% in volume fraction, respectively. The experimental results show that the existence of undissolved ferrite can increase the contact fatigue life The contact fatigue life can be prolonged with increasing the amounts of undissolved ferrite The grain size can be fined by using subcritical quenching process and the area of phase boundaries can also be greatly increased. The stress relaxation and grain refinement due to occurring of plastic deformation are main reasons for improving the fatigue life. The existence of undissolved ferrite can increase the crack initiation period. Under the experiment conditions, when the amount of undissolved ferrite is 10%, the longest contact fatigue life can be the obtained.

19. Influence of Asymmetrical Waveform on Low-Cycle Fatigue Life of Micro Solder Joint

Science.gov (United States)

Kanda, Yoshihiko; Kariya, Yoshiharu

2010-02-01

The effects of waveform symmetry on the low-cycle fatigue life of the Sn-3.0Ag-0.5Cu alloy have been investigated, using micro solder joint specimens with approximately the same volume of solder as is used in actual products. Focusing on crack initiation life, fatigue tests on Sn-Ag-Cu micro solder joints using asymmetrical triangular waveforms revealed no significant reduction in fatigue life. A slight reduction in fatigue life at low strain ranges caused by an increase in the fatigue ductility exponent, which is the result of a weakening microstructure due to loads applied at high temperature for long testing time, was observed. This was due to the fact that grain boundary damage, which has been reported in large-size specimens subjected to asymmetrical triangular waveforms, does not occur in Sn-Ag-Cu micro size solder joints with only a small number of crystal grain boundaries.

20. Impact of depression, fatigue and disability on quality of life in Chinese patients with multiple sclerosis.

Science.gov (United States)

Chen, Kelong; Fan, Yongping; Hu, Rui; Yang, Tao; Li, Kangning

2013-04-01

The aim of this work is to investigate and analyze the main factors that influence the quality of life (QOL) of multiple sclerosis (MS) patients. The QOL (multiple sclerosis impact scale), disability (expanded disability status scale), fatigue (modified fatigue impact scale) and depression (Beck Depression Inventory) were assessed in 100 MS patients. Correlation analysis shows that QOL is positively correlated with disability status, fatigue and depression, i.e., the more severe the disability, fatigue and depression, the worse the QOL. Multiple linear regression analysis indicated that Expanded Disability Status Scale grade and fatigue have important predictive value on the somatic QOL of MS patients. On the other hand, depression and fatigue have important predictive value on the mental QOL of MS patients. The QOL of MS patients is influenced by various factors, nursing care that focuses on patient disability, fatigue and depression should be strengthened. Copyright © 2012 John Wiley & Sons, Ltd.

1. Evaluation of Pressurization Fatigue Life of 1441 Al-li Fuselage Panel

Science.gov (United States)

Bird, R. Keith; Dicus, Dennis I.; Fridlyander, Joseph; Davydov, Valentin

1999-01-01

A study was conducted to evaluate the pressurization fatigue life of fuselage panels with skins fabricated from 1441 Al-Li, an attractive new Russian alloy. The study indicated that 1441 Al-Li has several advantages over conventional aluminum fuselage skin alloy with respect to fatigue behavior. Smooth 1441 Al-Li sheet specimens exhibited a fatigue endurance limit similar to that for 1163 Al (Russian version of 2024 Al) sheet. Notched 1441 Al-Li sheet specimens exhibited greater fatigue strength and longer fatigue life than 1163 Al. In addition, Tu-204 fuselage panels fabricated by Tupolev Design Bureau using Al-Li skin and ring frames with riveted 7000-series aluminum stiffeners had longer pressurization fatigue lives than did panels constructed from conventional aluminum alloys. Taking into account the lower density of this alloy, the results suggest that 1441 Al-Li has the potential to improve fuselage performance while decreasing structural weight.

2. Test Population Selection from Weibull-Based, Monte Carlo Simulations of Fatigue Life

Science.gov (United States)

Vlcek, Brian L.; Zaretsky, Erwin V.; Hendricks, Robert C.

2012-01-01

Fatigue life is probabilistic and not deterministic. Experimentally establishing the fatigue life of materials, components, and systems is both time consuming and costly. As a result, conclusions regarding fatigue life are often inferred from a statistically insufficient number of physical tests. A proposed methodology for comparing life results as a function of variability due to Weibull parameters, variability between successive trials, and variability due to size of the experimental population is presented. Using Monte Carlo simulation of randomly selected lives from a large Weibull distribution, the variation in the L10 fatigue life of aluminum alloy AL6061 rotating rod fatigue tests was determined as a function of population size. These results were compared to the L10 fatigue lives of small (10 each) populations from AL2024, AL7075 and AL6061. For aluminum alloy AL6061, a simple algebraic relationship was established for the upper and lower L10 fatigue life limits as a function of the number of specimens failed. For most engineering applications where less than 30 percent variability can be tolerated in the maximum and minimum values, at least 30 to 35 test samples are necessary. The variability of test results based on small sample sizes can be greater than actual differences, if any, that exists between materials and can result in erroneous conclusions. The fatigue life of AL2024 is statistically longer than AL6061 and AL7075. However, there is no statistical difference between the fatigue lives of AL6061 and AL7075 even though AL7075 had a fatigue life 30 percent greater than AL6061.

3. Aspects of fatigue life in thermal barrier coatings

Energy Technology Data Exchange (ETDEWEB)

Brodin, H.

2001-08-01

Thermal barrier coatings (TBC) are applied on hot components in airborne and land based gas turbines when higher turbine inlet temperature, meaning better thermal efficiency, is desired. The TBC is mainly applied to protect underlying material from high temperatures, but also serves as a protection from the aggressive corrosive environment. Plasma sprayed coatings are often duplex TBC's with an outer ceramic top coat (TC) made from partially stabilised zirconia - ZrO{sub 2} + 6-8% Y{sub 2}O{sub 3}. Below the top coat there is a metallic bond coat (BC). The BC is normally a MCrAlX coating (M=Ni, Co, Fe... and X=Y, Hf, Si ... ). In gas turbine components exposed to elevated temperatures nickel-based superalloys are commonly adopted as load carrying components. In the investigations performed here a commercial wrought Ni-base alloy Haynes 230 has been used as substrate for the TBC. As BC a NiCoCrAlY serves as a reference material and in all cases 7% Yttria PS zirconia has been used. Phase development and failure mechanisms in APS TBC during service-like conditions, have been evaluated in the present study. This is done by combinations of thermal cycling and low cycle fatigue tests. The aim is to achieve better knowledge regarding how, when and why thermal barrier coatings fail. As a final outcome of the project a model capable of predicting fatigue life of a given component will help engineers and designers of land based gas turbines for power generation to better optimise TBC's. In the investigations it is seen that TBC life is strongly influenced by oxidation of the BC and interdiffusion between BC and the substrate. The bond coat is known to oxidise with time at high temperature. The initial oxide found during testing is alumina. With increased time at high temperature Al is depleted from the bond coat due to inter-diffusion and oxidation. Oxides others than alumina start to form when the Al content is reduced below a critical limit. It is here believed

4. A review on fatigue life prediction methods for anti-vibration rubber materials

Directory of Open Access Journals (Sweden)

Xiaoli WANG

2016-08-01

Full Text Available Anti-vibration rubber, because of its superior elasticity, plasticity, waterproof and trapping characteristics, is widely used in the automotive industry, national defense, construction and other fields. The theory and technology of predicting fatigue life is of great significance to improve the durability design and manufacturing of anti-vibration rubber products. According to the characteristics of the anti-vibration rubber products in service, the technical difficulties for analyzing fatigue properties of anti-vibration rubber materials are pointed out. The research progress of the fatigue properties of rubber materials is reviewed from three angles including methods of fatigue crack initiation, fatigue crack propagation and fatigue damage accumulation. It is put forward that some nonlinear characteristics of rubber under fatigue loading, including the Mullins effect, permanent deformation and cyclic stress softening, should be considered in the further study of rubber materials. Meanwhile, it is indicated that the fatigue damage accumulation method based on continuum damage mechanics might be more appropriate to solve fatigue damage and life prediction problems for complex rubber materials and structures under fatigue loading.

5. An Energy-Critical Plane Based Fatigue Damage Approach for the Life Prediction of Metal Alloys

Science.gov (United States)

Pitatzis, N.; Savaidis, G.

2016-11-01

This paper presents a new energy-critical plane based fatigue damage approach for the assessment of the fatigue life under uniaxial and multiaxial proportional and non-proportional fatigue loading. The proposed approximate method, based on Farahani's multiaxial fatigue damage model, takes into account the critical plane orientations during a loading cycle and the values of the respective damage parameters on them. The uniqueness of the proposed method lies on the fact that it considers a weighted contribution of each critical plane orientation to the material damage. The relative weighting factors depend on the declination of each critical plane with respect to the critical plane, where the damage parameters exhibit their maximum values during a fatigue loading cycle. Herein, several low, mid and high-cycle fatigue loading cases are being investigated. The induced elastic-plastic stress-strain states are approximated by means of respective finite element analyses (FEA). Several experimental fatigue data derived from uniaxial and multiaxial fatigue tests on StE460 steel alloy thin-walled hourglass-type specimens have been used to verify the model's calculation accuracy. Comparison of experimental and calculated fatigue lives confirm remarkable fatigue life calculation accuracy in all cases examined.

6. Factors Affecting Quality of Life and Fatigue in Gynaecologic Cancer Patients

Directory of Open Access Journals (Sweden)

Güngör İ

2017-06-01

Full Text Available Background: Cancer-related fatigue (CRF is the most commonly reported and most distressing symptom in cancer patients. Health-related quality of life (QOL is an important outcome in cancer management, the authors sought to better understand its determinants. Aim: This study aims to identify quality of life and fatigue levels and the affecting factors in gynaecologic cancer patients. Method: This descriptive and cross-sectional study was conducted with 154 volunteer women with gynaecologic cancer. The data were collected through the interview form, functional assessment of cancer therapy-general (FACT-G Quality of Life Scale, and Piper Fatigue Scale. Results: The mean score of total quality of life in gynaecologic cancer patients was low, 53.4 ± 15.4. Physical and emotional states were found to be the mostly affected states in the quality of life. According to the Piper Fatigue Scale, the total fatigue score was mild, 3.5 ± 2.4. Total fatigue scores were found to be high in metastatic cancers. Multivariate analyses indicate that the most important factor affecting the quality of life is economic condition, and the most important variables affecting fatigue are the level of activity and use of medicine. Conclusion: This study found that quality of life dimensions in women with gynaecologic cancer was affected by factors such as cancer type, time of diagnosis, and stage and spread of the cancer.

7. Evaluation of Fatigue Life of CRM-Reinforced SMA and Its Relationship to Dynamic Stiffness

Directory of Open Access Journals (Sweden)

Nuha Salim Mashaan

2014-01-01

Full Text Available Fatigue cracking is an essential problem of asphalt concrete that contributes to pavement damage. Although stone matrix asphalt (SMA has significantly provided resistance to rutting failure, its resistance to fatigue failure is yet to be fully addressed. The aim of this study is to evaluate the effect of crumb rubber modifier (CRM on stiffness and fatigue properties of SMA mixtures at optimum binder content, using four different modification levels, namely, 6%, 8%, 10%, and 12% CRM by weight of the bitumen. The testing undertaken on the asphalt mix comprises the dynamic stiffness (indirect tensile test, dynamic creep (repeated load creep, and fatigue test (indirect tensile fatigue test at temperature of 25°C. The indirect tensile fatigue test was conducted at three different stress levels (200, 300, and 400 kPa. Experimental results indicate that CRM-reinforced SMA mixtures exhibit significantly higher fatigue life compared to the mixtures without CRM. Further, higher correlation coefficient was obtained between the fatigue life and resilient modulus as compared to permanent strain; thus resilient modulus might be a more reliable indicator in evaluating the fatigue life of asphalt mixture.

8. Evaluation of Fatigue Life of CRM-Reinforced SMA and Its Relationship to Dynamic Stiffness

Science.gov (United States)

Mashaan, Nuha Salim; Karim, Mohamed Rehan; Abdel Aziz, Mahrez; Ibrahim, Mohd Rasdan; Katman, Herda Yati

2014-01-01

Fatigue cracking is an essential problem of asphalt concrete that contributes to pavement damage. Although stone matrix asphalt (SMA) has significantly provided resistance to rutting failure, its resistance to fatigue failure is yet to be fully addressed. The aim of this study is to evaluate the effect of crumb rubber modifier (CRM) on stiffness and fatigue properties of SMA mixtures at optimum binder content, using four different modification levels, namely, 6%, 8%, 10%, and 12% CRM by weight of the bitumen. The testing undertaken on the asphalt mix comprises the dynamic stiffness (indirect tensile test), dynamic creep (repeated load creep), and fatigue test (indirect tensile fatigue test) at temperature of 25°C. The indirect tensile fatigue test was conducted at three different stress levels (200, 300, and 400 kPa). Experimental results indicate that CRM-reinforced SMA mixtures exhibit significantly higher fatigue life compared to the mixtures without CRM. Further, higher correlation coefficient was obtained between the fatigue life and resilient modulus as compared to permanent strain; thus resilient modulus might be a more reliable indicator in evaluating the fatigue life of asphalt mixture. PMID:25050406

9. Evaluation of fatigue life of CRM-reinforced SMA and its relationship to dynamic stiffness.

Science.gov (United States)

Mashaan, Nuha Salim; Karim, Mohamed Rehan; Abdel Aziz, Mahrez; Ibrahim, Mohd Rasdan; Katman, Herda Yati; Koting, Suhana

2014-01-01

Fatigue cracking is an essential problem of asphalt concrete that contributes to pavement damage. Although stone matrix asphalt (SMA) has significantly provided resistance to rutting failure, its resistance to fatigue failure is yet to be fully addressed. The aim of this study is to evaluate the effect of crumb rubber modifier (CRM) on stiffness and fatigue properties of SMA mixtures at optimum binder content, using four different modification levels, namely, 6%, 8%, 10%, and 12% CRM by weight of the bitumen. The testing undertaken on the asphalt mix comprises the dynamic stiffness (indirect tensile test), dynamic creep (repeated load creep), and fatigue test (indirect tensile fatigue test) at temperature of 25°C. The indirect tensile fatigue test was conducted at three different stress levels (200, 300, and 400 kPa). Experimental results indicate that CRM-reinforced SMA mixtures exhibit significantly higher fatigue life compared to the mixtures without CRM. Further, higher correlation coefficient was obtained between the fatigue life and resilient modulus as compared to permanent strain; thus resilient modulus might be a more reliable indicator in evaluating the fatigue life of asphalt mixture.

10. Quality of life and energy expenditure in transplant recipient football players.

Science.gov (United States)

Totti, V; Zancanaro, M; Trerotola, M; Nanni Costa, A; Antonetti, T; Anedda, A; Roi, G S

2013-09-01

Football (soccer) is a highly motivating leisure activity with important potential as a health-promoting activity also for transplant recipients. The aim of this study was to assess the "on the field" energy expenditure during football games and the quality of life of transplant recipients practicing football. Twenty-two recipients of kidney (n = 11), bone marrow (n = 7), liver (n = 3) or corneal (n = 1) transplantations had an overall mean age of 37 ± 9 years, body mass index of 23.5 ± 2.4 kg/m(2), and time after transplantation of 9.3 ± 6.4 years. They were compared with 25 healthy football players of mean age 41 ± 10 years and body mass index of 26.3 ± 3.9 kg/m(2). There were no significant differences between transplant recipients and controls regarding mean energy expenditure (393 ± 113 vs 392 ± 132 kcal/h) number of steps (3.978 ± 1.317 vs 3.933 ± 1.563) during, and capillary blood lactate concentrations (4.8 ± 0.9 vs 5.2 ± 1.3 mmol/L) after the matches. The SF-36 questionnaire administered before the matches showed transplant recipient players to score significantly worse in the scales of general (P football matches attained a level of energy expenditure and a quality of life consistent with a healthy lifestyle. Football has the potential to be implemented as a permanent health-promoting activity also for transplant recipients.

11. Laser Shock Peening of Aluminum Alloy 7050 for Fatigue Life Improvement

Institute of Scientific and Technical Information of China (English)

Qian; Ming; Lian; Ying; Zou; Shikun; Gong; Shuili

2007-01-01

The effects of laser shock peening (LSP) on improving fatigue life of aluminum alloy 7050 are investigated.Surface hardness is increased corresponding to a high dislocation density induced by LSP.The X-ray diffraction stress measurement shows that LSP results in prominent increase of surface compressive stress,quasi-symmetrically distributed in the laser peened region.The fatigue life of the alloy 7050 in rivet fastener hole structure is notably improved owing to LSP.The sequence of LSP and fastener hole preparation also influence the fatigue cycle life of the alloy.

12. Modeling of fatigue life of materials and structures under low-cycle loading

Science.gov (United States)

Volkov, I. A.; Korotkikh, Yu. G.

2014-05-01

A damaged medium model (DMM) consisting of three interconnected components (relations determining the cyclic elastoplastic behavior of the material, kinetic damage accumulation equations, and the strength criterion for the damaged material) was developed to estimate the stress strain state and the fatigue life of important engineering objects. The fatigue life of a strip with a cut under cyclic loading was estimated to obtain qualitative and quantitative estimates of the DMM constitutive relations under low-cycle loading. It was shown that the considered version of the constitutive relations reliably describes the main effects of elastoplastic deformation and the fatigue life processes of materials and structures.

13. Relation between Shot Peening Process and Fatigue Life in the Case of Hardening Steels

Institute of Scientific and Technical Information of China (English)

SHIGEYOSHI HAGA; HARUSHIGE TSUBAKINO; YASUNORI HARADA

2004-01-01

Nowadays, in the auto industry, the need for improvement of fuel efficiency is getting increased more and more in terms of the global warming, as well as the need of light-weighting of gears, transmission parts. Hence, we've studied the relation between the shot peening working conditions and factors for improvement of gear's fatigue life, and also the relation between the factors for improvement and the fatigue life, applying shot peening to a gear of SNCM220. Also, we examined the relation between the fatigue life and arc height that is utilized as a substitute characteristic for shot peening working conditions, adding its observation here.

14. A Simple Fatigue Life Prediction Algorithm Using the Modified NASGRO Equation

Directory of Open Access Journals (Sweden)

Wei Zhang

2016-01-01

Full Text Available A simple fatigue life prediction algorithm using the modified NASGRO equation is proposed in this paper. The NASGRO equation is modified by introducing the concept of intrinsic effective threshold stress intensity factor (SIF range ΔKeffth. One advantage of the proposed method is that the complex growth behavior analysis of small cracks can be avoided, and then the fatigue life can be calculated by directly integrating the crack growth model from the initial defect size to the critical crack size. The fatigue limit and the intrinsic effective threshold SIF range ΔKeffth are used to calculate the initial defect size or initial flaw size. The value of ΔKeffth is determined by extrapolating the crack propagation rate curves. Instead of using the fatigue limit determined by the fatigue strength at the specific fatigue life, the fatigue limit is selected based on the horizontal tendency of the S-N curve. The calculated fatigue lives are compared to the experimental data of two different alloys. The predicted S-N curves agree with the test data well. Besides, the prediction results are compared with that calculated using the FASTRAN code. Results indicate that the proposed life prediction algorithm is simple and efficient.

15. Fatigue and quality of life in breast cancer survivors: temporal courses and long-term pattern

NARCIS (Netherlands)

Schmidt, M.E.; Chang-Claude, J.; Vrieling, A.; Heinz, J.; Flesch-Janys, D.; Steindorf, K.

2012-01-01

INTRODUCTION: Fatigue is a frequent problem during and after cancer treatment. We investigated different courses of fatigue from pre-diagnosis, through therapy, to long-term survivorship and evaluated potential implications on long-term quality of life (QoL). METHODS: Breast cancer patients diagnose

16. Impact of fatigue on quality of life in patients with Parkinson's disease

NARCIS (Netherlands)

Havlikova, E.; Rosenberger, J.; Nagyova, I.; Middel, B.; Dubayova, T.; Gdovinova, Z.; van Dijk, J. P.; Groothoff, J. W.

2008-01-01

Background and purpose: Fatigue is frequent and important in the lives of Parkinson's disease (PD) patients. It is multidimensional, with physical and mental aspects. The aim of our study was to explore the impact of fatigue on quality of life (QoL) for PD patients. Methods: The sample consisted of

17. Probabilistic Modelling of Fatigue Life of Composite Laminates Using Bayesian Inference

DEFF Research Database (Denmark)

Dimitrov, Nikolay Krasimirov; Kiureghian, Armen Der

2014-01-01

A probabilistic model for estimating the fatigue life of laminated composite plates subjected to constant-amplitude or variable-amplitude loading is developed. The model is based on lamina-level input data, making it possible to predict fatigue properties for a wide range of laminate configuratio...

18. Fatigue Life Prediction of Metallic Materials Based on the Combined Nonlinear Ultrasonic Parameter

Science.gov (United States)

Zhang, Yuhua; Li, Xinxin; Wu, Zhenyong; Huang, Zhenfeng; Mao, Hanling

2017-07-01

The fatigue life prediction of metallic materials is always a tough problem that needs to be solved in the mechanical engineering field because it is very important for the secure service of mechanical components. In this paper, a combined nonlinear ultrasonic parameter based on the collinear wave mixing technique is applied for fatigue life prediction of a metallic material. Sweep experiments are first conducted to explore the influence of driving frequency on the interaction of two driving signals and the fatigue damage of specimens, and the amplitudes of sidebands at the difference frequency and sum frequency are tracked when the driving frequency changes. Then, collinear wave mixing tests are carried out on a pair of cylindrically notched specimens with different fatigue damage to explore the relationship between the fatigue damage and the relative nonlinear parameters. The experimental results show when the fatigue degree is below 65% the relative nonlinear parameter increases quickly, and the growth rate is approximately 130%. If the fatigue degree is above 65%, the increase in the relative nonlinear parameter is slow, which has a close relationship with the microstructure evolution of specimens. A combined nonlinear ultrasonic parameter is proposed to highlight the relationship of the relative nonlinear parameter and fatigue degree of specimens; the fatigue life prediction model is built based on the relationship, and the prediction error is below 3%, which is below the prediction error based on the relative nonlinear parameters at the difference and sum frequencies. Therefore, the combined nonlinear ultrasonic parameter using the collinear wave mixing method can effectively estimate the fatigue degree of specimens, which provides a fast and convenient method for fatigue life prediction.

19. Fatigue Life Prediction of Metallic Materials Based on the Combined Nonlinear Ultrasonic Parameter

Science.gov (United States)

Zhang, Yuhua; Li, Xinxin; Wu, Zhenyong; Huang, Zhenfeng; Mao, Hanling

2017-08-01

The fatigue life prediction of metallic materials is always a tough problem that needs to be solved in the mechanical engineering field because it is very important for the secure service of mechanical components. In this paper, a combined nonlinear ultrasonic parameter based on the collinear wave mixing technique is applied for fatigue life prediction of a metallic material. Sweep experiments are first conducted to explore the influence of driving frequency on the interaction of two driving signals and the fatigue damage of specimens, and the amplitudes of sidebands at the difference frequency and sum frequency are tracked when the driving frequency changes. Then, collinear wave mixing tests are carried out on a pair of cylindrically notched specimens with different fatigue damage to explore the relationship between the fatigue damage and the relative nonlinear parameters. The experimental results show when the fatigue degree is below 65% the relative nonlinear parameter increases quickly, and the growth rate is approximately 130%. If the fatigue degree is above 65%, the increase in the relative nonlinear parameter is slow, which has a close relationship with the microstructure evolution of specimens. A combined nonlinear ultrasonic parameter is proposed to highlight the relationship of the relative nonlinear parameter and fatigue degree of specimens; the fatigue life prediction model is built based on the relationship, and the prediction error is below 3%, which is below the prediction error based on the relative nonlinear parameters at the difference and sum frequencies. Therefore, the combined nonlinear ultrasonic parameter using the collinear wave mixing method can effectively estimate the fatigue degree of specimens, which provides a fast and convenient method for fatigue life prediction.

20. Fatigue, mood and quality of life improve in MS patients after progressive resistance training

DEFF Research Database (Denmark)

Dalgas, U; Stenager, E; Petersen, T

2010-01-01

. Fatigue (Fatigue Severity Scale, FSS), mood (Major Depression Inventory, MDI) and quality of life (physical and mental component scores, PCS and MCS, of SF36) were scored at start, end and follow-up of a randomized controlled clinical trial of 12 weeks of progressive resistance training in moderately...... disabled (Expanded Disability Status Scale, EDSS: 3-5.5) multiple sclerosis patients including a Control group (n = 15) and an Exercise group (n = 16). Fatigue (FSS > 4) was present in all patients. Scores of FSS, MDI, PCS-SF36 and MCS-SF36 were comparable at start of study in the two groups. Fatigue...

1. Fatigue Life Analysis of Tapered Hybrid Composite Flexbeams

Science.gov (United States)

Murri, Gretchen B.; Schaff, Jeffery R.; Dobyns, Alan L.

2002-01-01

Nonlinear-tapered flexbeam laminates from a full-size composite helicopter rotor hub flexbeam were tested under combined constant axial tension and cyclic bending loads. The two different graphite/glass hybrid configurations tested under cyclic loading failed by delamination in the tapered region. A 2-D finite element model was developed which closely approximated the flexbeam geometry, boundary conditions, and loading. The analysis results from two geometrically nonlinear finite element codes, ANSYS and ABAQUS, are presented and compared. Strain energy release rates (G) obtained from the above codes using the virtual crack closure technique (VCCT) at a resin crack location in the flexbeams are presented for both hybrid material types. These results compare well with each other and suggest that the initial delamination growth from the resin crack toward the thick region of the flexbeam is strongly mode II. The peak calculated G values were used with material characterization data to calculate fatigue life curves and compared with test data. A curve relating maximum surface strain to number of loading cycles at delamination onset compared reasonably well with the test results.

2. Fatigue Life Methodology for Tapered Hybrid Composite Flexbeams

Science.gov (United States)

urri, Gretchen B.; Schaff, Jeffery R.

2006-01-01

Nonlinear-tapered flexbeam specimens from a full-size composite helicopter rotor hub flexbeam were tested under combined constant axial tension and cyclic bending loads. Two different graphite/glass hybrid configurations tested under cyclic loading failed by delamination in the tapered region. A 2-D finite element model was developed which closely approximated the flexbeam geometry, boundary conditions, and loading. The analysis results from two geometrically nonlinear finite element codes, ANSYS and ABAQUS, are presented and compared. Strain energy release rates (G) associated with simulated delamination growth in the flexbeams are presented from both codes. These results compare well with each other and suggest that the initial delamination growth from the tip of the ply-drop toward the thick region of the flexbeam is strongly mode II. The peak calculated G values were used with material characterization data to calculate fatigue life curves for comparison with test data. A curve relating maximum surface strain to number of loading cycles at delamination onset compared well with the test results.

3. Fatigue life of high strength steel for cold forming

Directory of Open Access Journals (Sweden)

R. Ulewicz

2017-01-01

Full Text Available The article presents the results of fatigue tests carried out on STRENX-type high-strength cold forming steel. For high-cycle fatigue tests carried out using low cycle loading frequencies of around 30 Hz, a ROTOFLEX machine was used. For ultra high-cycle tests, a KAUP-ZU testing machine was employed, which enables fatigue tests to be performed with symetric specimen loading (R = -1 and at a frequency of f ≈ 20 kHz. The relationships σa = f(N were determined experimentally in the high and ultra high-cycle region for STRENX high-strength steel. To determine the fatigue crack initiation mechanism, the fractographic analysis of fatigue fractures was made.

4. Fatigue life prediction method for contact wire using maximum local stress

Energy Technology Data Exchange (ETDEWEB)

Kim, Yong Seok; Haochuang, Li; Seok, Chang Sung; Koo, Jae Mean [Sungkyunkwan University, Suwon (Korea, Republic of); Lee, Ki Won; Kwon, Sam Young; Cho, Yong Hyeon [Korea Railroad Research Institute, Uiwang (Korea, Republic of)

2015-01-15

Railway contact wires supplying electricity to trains are exposed to repeated mechanical strain and stress caused by their own weight and discontinuous contact with a pantograph during train operation. Since the speed of railway transportation has increased continuously, railway industries have recently reported a number of contact wire failures caused by mechanical fatigue fractures instead of normal wear, which has been a more common failure mechanism. To secure the safety and durability of contact wires in environments with increased train speeds, a bending fatigue test on contact wire has been performed. The test equipment is too complicated to evaluate the fatigue characteristics of contact wire. Thus, the axial tension fatigue test was performed for a standard specimen, and the bending fatigue life for the contact wire structure was then predicted using the maximum local stress occurring at the top of the contact wire. Lastly, the tested bending fatigue life of the structure was compared with the fatigue life predicted by the axial tension fatigue test for verification.

5. Fatigue Life Prediction of Horizontal Press Frame Based on Statistical Probability and Its Redesign

Institute of Scientific and Technical Information of China (English)

WeiWei Zhang; XiaoSon Wang; Bo Yang; Shi-Jian Yuan

2014-01-01

Horizontal press as an important part of hydro-forming machine is used to output the horizontal force to keep the high internal pressure during tube hydro-forming. However, the horizontal press frame is usually mounted on the press bed and not pre-stressed. Meanwhile it will be subjected to the reaction force caused by liquid pressure. Stresses are concentrated severely on the assemble region due to deformation, and total fatigue life will decrease. In order to predict the total fatigue life of the frame, the simulations are used firstly to determine to stress concentration region, and then strain gauge measurements are carried out under different loads. Next, the methods of statistical probability are conducted to calculate the fatigue life based on long-term load history. Finally a structure with the considerable longer fatigue life is redesigned.

6. Extreme Environment Damage Index and Accumulation Model for CMC Laminate Fatigue Life Prediction Project

Data.gov (United States)

National Aeronautics and Space Administration — Materials Research & Design (MR&D) is proposing in the SBIR Phase II an effort to develop a tool for predicting the fatigue life of C/SiC composite...

7. Effect of various drilling procedures on the fatigue life of rivet holes ...

African Journals Online (AJOL)

Synthèse: Revue des Sciences et de la Technologie ... In addition, the machining process used for drilling can increase or decrease the fatigue life of materials. ... and surface quality observed using a scanning electron microscopy (SEM).

8. Fatigue life prediction of casing welded pipes by using the extended finite element method

National Research Council Canada - National Science Library

Ljubica Lazi; Aleksandar Raji; Aleksandar Grbovi; Aleksandar Sedmak; e Sarko

2016-01-01

The extended finite element (XFEM) method has been used to simulate fatigue crack growth in casing pipe, made of API J55 steel by high-frequency welding, in order estimate its structural integrity and life...

9. What roles do team climate, roster control, and work life conflict play in shiftworkers' fatigue longitudinally?

Science.gov (United States)

Pisarski, Anne; Barbour, Jennifer P

2014-05-01

The study aimed to examine shiftworkers fatigue and the longitudinal relationships that impact on fatigue such as team climate, work life conflict, control of shifts and shift type in shift working nurses. We used a quantitative survey methodology and analysed data with a moderated hierarchical multiple regression. After matching across two time periods 18 months apart, the sample consisted of 166 nurses from one Australian hospital. Of these nurses, 61 worked two rotating day shifts (morning & afternoon/evening) and 105 were rotating shiftworkers who worked three shifts (morning afternoon/evening and nights). The findings suggest that control over shift scheduling can have significant effects on fatigue for both two-shift and three-shift workers. A significant negative relationship between positive team climate and fatigue was moderated by shift type. At both Time 1 and Time 2, work life conflict was the strongest predictor of concurrent fatigue, but over time it was not.

10. Modeling the effects of control systems of wind turbine fatigue life

Energy Technology Data Exchange (ETDEWEB)

Pierce, K.G.; Laino, D.J. [Univ. of Utah, Salt Lake City, UT (United States)

1996-12-31

In this study we look at the effect on fatigue life of two types of control systems. First, we investigate the Micon 65, an upwind, three bladed turbine with a simple yaw control system. Results indicate that increased fatigue damage to the blade root can be attributed to continuous operation at significant yaw error allowed by the control system. Next, we model a two-bladed teetered rotor turbine using three different control systems to adjust flap deflections. The first two limit peak power output, the third limits peak power and cyclic power output over the entire range of operation. Results for simulations conducted both with and without active control are compared to determine how active control affects fatigue life. Improvement in fatigue lifetimes were seen for all control schemes, with increasing fatigue lifetime corresponding to increased flap deflection activity. 13 refs., 6 figs., 2 tabs.

11. Voltage sag influence on fatigue life of the drivetrain of fixed speed wind turbines

DEFF Research Database (Denmark)

Veluri, Badrinath; Santos-Martin, David; Jensen, Henrik Myhre

2011-01-01

on the fatigue life of important drivetrain components. The high penetration of wind energy in the electrical grids demands new requirements for the operation of wind energy conversion systems. Although fixed speed wind turbine technology is nowadays replaced by variable speed wind turbines. In some countries...... effect on the fatigue life of drivetrain components. The capability to simulate these phenomena is a novel aspect in the present effort....

12. The prediction technology study of fatigue life for key parts of a tracked vehicle's suspension system

Institute of Scientific and Technical Information of China (English)

WANG Hongyan; RUI Qiang; HE Xiaojun

2007-01-01

In allusion to fatigue life of a tracked vehicle torsion bar, a virtual prototype model of the tracked vehicle suspension system including a flexible torsion bar was built based on dynamic simulation software-ADAMS. Node force and stress results of the torsion bar from last step simu- lation were acquired; taking into account the material charac- teristics and influential factors, fatigue life of the flexible body. of the torsion bar was predicted. Engineering results can be acquired through the contrast of the result of virtual test and statistical fatigue.

13. The fatigue life of a cobalt-chromium alloy after laser welding.

Science.gov (United States)

Al-Bayaa, Nabil Jalal Ahmad; Clark, Robert K F; Juszczyk, Andrzej S; Radford, David R

2011-03-01

The aim of this study was to investigate the fatigue life of laser welded joints in a commercially available cast cobalt-chromium alloy. Twenty rod shaped specimens (40 mm x 1.5 mm) were cast and sand blasted. Ten specimens were used as controls and the remaining ten were sectioned and repaired using a pulsed Nd: YAG laser welder. All specimens were subjected to fatigue testing (30N - 2Hz) in a controlled environment. A statistically significant difference in median fatigue life was found between as-cast and laser welded specimens (p welded specimens despite 70% penetration of the weld.

14. Estimation of the Residual Fatigue Life of Laminated Composites Under a Multistage Cyclic Loading

Science.gov (United States)

Strizhius, V.

2016-11-01

Problems on estimation of the residual fatigue life of laminated composites under a multistage regular cyclic loading (with a constant amplitude at each loading stage) are among the most frequently ones encountered in the practice of fatigue life estimations of laminated composites. There are several methods for solving these problems, but their use not always gives results of acceptable accuracy. To improve the accuracy of such estimations for the type of cyclic loading mentioned, a special model of nonlinear accumulation of fatigue damage is proposed.

15. Fatigue Life of High Performance Grout in Dry and Wet Environment for Wind Turbine Grouted Connections

DEFF Research Database (Denmark)

Sørensen, Eigil V.

2011-01-01

the fatigue life of a high performance cement based grout was tested by dynamic compressive loading of cylindrical specimens at varying levels of cyclic frequency and load. The fatigue tests were performed in two series, one with the specimens tested in air and one with the specimens submerged in water during...... the test. The fatigue life of the grout, in terms of the number of cycles to failure, was found to be significantly shorter when tested in water than when tested in air, particularly at low frequency....

16. Fatigue Life of Stainless Steel in PWR Environments with Strain Holding

Energy Technology Data Exchange (ETDEWEB)

Kim, Taesoon; Kim, Kyuhyung [KHNP CRI, Daejeon (Korea, Republic of); Seo, Myeonggyu; Jang, Changheui [KAIST, Daejeon (Korea, Republic of)

2016-10-15

Many components and structures of nuclear power plants are exposed to the water chemistry conditions during the operation. Recently, as design life of nuclear power plant is expanded over 60 years, the environmentally assisted fatigue (EAF) due to these water chemistry conditions has been considered as one of the important damage mechanisms of the safety class 1 components. Therefore, many studies to evaluate the effect of light water reactor (LWR) coolant environments on fatigue life of materials have been conducted. Many EAF test results including Argonne National Laboratory’s consistently indicated the substantial reduction of fatigue life in the light water reactor environments. However, there is a discrepancy between laboratory test data and plant operating experience regarding the effects of environment on fatigue: while laboratory test data suggest huge accumulation of fatigue damage, very limited experience of cracking caused by the low cycle fatigue in light water reactor. These hold-time effect tests are preformed to characterize the effects of strain holding on the fatigue life of austenitic stainless steels in PWR environments in comparison with the existing fixed strain rate results. Low cycle fatigue life tests were conducted for the type 316 stainless steel in 310℃ air and PWR environments with triangular strain. In agreement with the previous reports, the LCF life was reduced in PWR environments. Also for the slower strain rate, the reduction of LCF life was greater than the faster strain rate. The LCF test conditions for the hold-time effects were determined by the references and consideration of actual plant transient. To simulate the heat-up and cooldown transient, sub-peak strain holding during the down-hill of strain amplitude was chosen instead of peak strain holding which used in the previous researches.

17. Development of a Novel Approach for Fatigue Life Prediction of Structural Materials

Science.gov (United States)

2008-12-01

11] for Inconel 718 under a similar loading condition. A kink around a fatigue life of 3xl05 cycles was noticed in the shear strain-life curve from...observed on AISI 304 stainless steel [10], Inconel 718 [11], 1045 steel [12], and an aluminum alloy [13]. However, no kink in the strain-life curves

Directory of Open Access Journals (Sweden)

C. Gourdin

2016-10-01

Full Text Available Fatigue lifetime assessment is essential in the design of structures. Under-estimated predictions may result in unnecessary in service inspections. Conversely, over-estimated predictions may have serious consequences on the integrity of structures. In some nuclear power plant components, the fatigue loading may be equibiaxial because of thermal fatigue. So the potential impact of multiaxial loading on the fatigue life of components is a major concern. Meanwhile, few experimental data are available on austenitic stainless steels. It is essential to improve the fatigue assessment methodologies to take into account the potential equi-biaxial fatigue damage. Hence this requires obtaining experimental data on the considered material with a strain tensor in equibiaxial tension. Two calibration tests (with strain gauges and image correlation were used to obtain the relationship between the imposed deflection and the radial strain on the FABIME2 specimen. A numerical study has confirmed this relationship. Biaxial fatigue tests are carried out on two austenitic stainless steels for different values of the maximum deflection, and with a load ratio equal to -1. The interpretation of the experimental results requires the use of an appropriate definition of strain equivalent. In nuclear industry, two kinds of definition are used: von Mises and TRESCA strain equivalent. These results have permitted to estimate the impact of the equibiaxiality on the fatigue life of components

19. Consideration on corrosion fatigue crack life assessment; Fushoku hiro kiretsu hassei jumyo hyoka ni kansuru ichikosatsu

Energy Technology Data Exchange (ETDEWEB)

Yajima, H.; Yamamoto, M.; Saito, T. [Hiroshima University, Hiroshima (Japan). Faculty of Engineering; Morita, K. [Mitsubishi Heavy Industries, Ltd., Tokyo (Japan)

1996-10-01

Discussions were given on corrosion fatigue crack life by using corrosion fatigue crack initiation test and analysis. The test used 13Cr-based stainless steel as a test material, and aquamarine at 60{degree}C as a corrosion environment. The fatigue test was performed under a tension loading condition with a stress ratio of 0.1 and an iterative velocity of 1.7 Hz by using a 10-tonf fatigue testing machine. In the corrosion fatigue crack initiation test, a pit has been generated on a boundary of an exposed part and a painted part for masking, hence direct observation was impossible on pit growth behavior. Therefore, an intrinsic crack model was introduced from pit dimensions as observed from a fracture face, and analysis was made on corrosion fatigue crack growth by using the linear fracture dynamics, wherein clarification was made on a phenomenon occurring after the crack growth passes the pit growth until the test piece is fractured. A proposal was made to define the time when fatigue crack initiates and grows from the bottom of a pit as a result of surpassing the growth of corrosion pit as the corrosion fatigue crack life. 4 refs., 7 figs., 1 tab.

20. Fatigue life on a full scale test rig: Forged versus cast wind turbine rotor shafts

Science.gov (United States)

Herrmann, J.; Rauert, T.; Dalhoff, P.; Sander, M.

2016-09-01

To reduce uncertainties associated with the fatigue life of the highly safety relevant rotor shaft and also to review today's design practice, the fatigue behaviour will be tested on a full scale test rig. Until now tests on full scale wind turbine parts are not common. Therefore, a general lack of experience on how to perform accelerated life time tests for those components exists. To clarify how to transfer real conditions to the test environment, the arrangements and deviations for the upcoming experimental test are discussed in detail. In order to complete investigations of weight saving potentials, next to getting a better comprehension of the fatigue behaviour by executing a full scale test, a further outcome are suggestions for the usage of cast and forged materials regarding the fatigue and the remaining life of the rotor shaft. It is shown, that it is worthwhile to think about a material exchange for the forged rotor shaft.

1. An Integrated Health Monitoring Method for Structural Fatigue Life Evaluation Using Limited Sensor Data

Directory of Open Access Journals (Sweden)

Jingjing He

2016-11-01

Full Text Available A general framework for structural fatigue life evaluation under fatigue cyclic loading using limited sensor data is proposed in this paper. First, limited sensor data are measured from various sensors which are preset on the complex structure. Then the strain data at remote spots are used to obtain the strain responses at critical spots by the strain/stress reconstruction method based on empirical mode decomposition (REMD method. All the computations in this paper are directly performed in the time domain. After the local stress responses at critical spots are determined, fatigue life evaluation can be performed for structural health management and risk assessment. Fatigue life evaluation using the reconstructed stresses from remote strain gauge measurement data is also demonstrated with detailed error analysis. Following this, the proposed methodology is demonstrated using a three-dimensional frame structure and a simplified airfoil structure. Finally, several conclusions and future work are drawn based on the proposed study.

2. Fatigue life of stainless steel 304 enhancement by addition of multi-walled carbon nanotubes (MWCNTs)

Energy Technology Data Exchange (ETDEWEB)

Syed, Rizwanulhaque; Jiang, Wei; Wang, Cunshan [Dalian University of Technology, Dalian (China); Sabir, M. Iqbal [Xiao Zhang County, Tianjin (China)

2015-01-15

Stainless steel is among the most widely used industrial materials. In particular, stainless steel 304 (304SS) is the most used material grade. To increase the utilization of any industrial material, its fatigue life should be optimized. In this work, the fatigue life of 304SS was enhanced by the addition of multi-walled carbon nanotubes (MWCNTs). Moreover, the incorporation of a small amount of MWCNTs increased the fatigue life of 304SS. Scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction (XRD) results showed that the suppression of fatigue crack growth rate was caused by CNT deposition at the crack tip. CNTs were entangled with each other, thereby resulting in finer grain size. The XRD diffractograms of the 304SS treated area peak showed that the microstructure consisted of austenite and carbon.

3. Fatigue Life of High Performance Grout in Dry and Wet Environment for Wind Turbine Grouted Connections

DEFF Research Database (Denmark)

Sørensen, Eigil V.

2011-01-01

The cementitious material in grouted connections of offshore monopile wind turbine structures is subjected to very high oscillating service stresses. The fatigue capacity of the grout therefore becomes essential to the performance and service life of the grouted connection. In the present work...... the fatigue life of a high performance cement based grout was tested by dynamic compressive loading of cylindrical specimens at varying levels of cyclic frequency and load. The fatigue tests were performed in two series, one with the specimens tested in air and one with the specimens submerged in water during...... the test. The fatigue life of the grout, in terms of the number of cycles to failure, was found to be significantly shorter when tested in water than when tested in air, particularly at low frequency....

4. Multiaxial Fatigue Life Prediction for Steels Based on Some Simple Approximations

Science.gov (United States)

Li, Jing; Yao, Zhi-feng; Zhang, Zhong-ping

2015-01-01

The Roessle-Fatemi's hardness method (HM) and Muralidharan-Manson's modified universal slopes method (MUSM) were employed to determine the uniaxial fatigue properties of steels from easily obtained tensile properties. Both methods give good life predictions, while the Roessle-Fatemi's HM is somewhat better. Furthermore, for predicting multiaxial fatigue lives of steels in the absence of any fatigue data, the Li's modified Wang-Brown model (MWB) was used in combination with the HM method (MWB-HM) as well as the MUSM method (MWB-MUSM), respectively. Correlation between the yield strength and the Brinell hardness was also developed to estimate the multiaxial fatigue lives of steels based only on hardness and elasticity modulus. It is shown that multiaxial fatigue lives were predicted fairly well by all the methods, and the MWB-MUSM method is slightly more accurate. In addition, a computer-based procedure for multiaxial fatigue life assessment incorporating MWB-MUSM approach was proposed and implemented to predict the fatigue life of an intermediate compressor casing. The predicted results are promising.

5. Effect of Applied Potential on Fatigue Life of Electropolished Nitinol Wires

Science.gov (United States)

Sivan, Shiril; Di Prima, Matthew; Weaver, Jason D.

2017-06-01

Nitinol is used as a metallic biomaterial in medical devices due to its shape memory and pseudoelastic properties. The clinical performance of nitinol depends on factors which include the surface finish, the local environment, and the mechanical loads to which the device is subjected. Preclinical evaluations of device durability are performed with fatigue tests while electrochemical characterization methods such as ASTM F2129 are employed to evaluate corrosion susceptibility by determining the rest potential and breakdown potential. However, it is well established that the rest potential of a metal surface can vary with the local environment. Very little is known regarding the influence of voltage on fatigue life of nitinol. In this study, we developed a fatigue testing method in which an electrochemical system was integrated with a rotary bend wire fatigue tester. Samples were fatigued at various strain levels at electropotentials anodic and cathodic to the rest potential to determine if it could influence fatigue life. Wires at potentials negative to the rest potential had a significantly higher number of cycles to fracture than wires held at potentials above the breakdown potential. For wires for which no potential was applied, they had fatigue life similar to wires at negative potentials.

6. Life prediction of thermal-mechanical fatigue using strain-range partitioning

Science.gov (United States)

Halford, G. R.; Manson, S. S.

1975-01-01

The applicability is described of the method of Strainrange Partitioning to the life prediction of thermal-mechanical strain-cycling fatigue. An in-phase test on 316 stainless steel is analyzed as an illustrative example. The observed life is in excellent agreement with the life predicted by the method using the recently proposed Step-Stress Method of experimental partitioning, the Interation Damage Rule, and the life relationships determined at an isothermal temperature of 705 C. Implications of the study are discussed relative to the general thermal fatigue problem.

7. Effect of vibration loading on the fatigue life of part-through notched pipe

Energy Technology Data Exchange (ETDEWEB)

Mittal, Rahul [Nuclear Power Corporation of India Limited, Mumbai (India); Singh, P.K., E-mail: singh_pawank@yahoo.com [Bhabha Atomic Research Centre, Mumbai (India); Pukazhendi, D.M. [Structural Engineering research Centre, Chennai (India); Bhasin, V.; Vaze, K.K.; Ghosh, A.K. [Bhabha Atomic Research Centre, Mumbai (India)

2011-10-15

8. Time and frequency domain models for multiaxial fatigue life estimation under random loading

Directory of Open Access Journals (Sweden)

Andrea Carpinteri

2015-07-01

Full Text Available Engineering structures and components are often subjected to random fatigue loading produced, for example, by wind turbulences, marine waves and vibrations. The methods available in the literature for fatigue assessment under random loading are formulated in time domain or, alternatively, in frequency domain. The former methods require the knowledge of the loading time history, and a large number of experimental tests/numerical simulations is needed to obtain statistically reliable results. The latter methods are generally more advantageous with respect to the time domain ones, allowing a rapid fatigue damage evaluation. In the present paper, a multiaxial criterion formulated in the frequency-domain is presented to estimate the fatigue lives of smooth metallic structures subjected to combined bending and torsion random loading. A comparison in terms of fatigue life prediction by employing a time domain methods, previously proposed by the authors, is also performed.

9. Home-Based Hospice Care Reduces End-of-Life Expenditure in Taiwan: A Population-Based Study.

Science.gov (United States)

Chen, Li-Fu; Chang, Chun-Ming; Huang, Chih-Yuan

2015-09-01

Inpatient hospice care can reduce futile treatment and medical costs. However, the cost trimming effect of home-based hospice care in hospital has yet not been explored. This study evaluates the impact of home-based hospice care on end-of-life expenditure in hospitals with different spending intensity. This is a population-based retrospective study in Taiwan. Cancer decedents were identified in the National Health Insurance Research Database (NHIRD) from 2009 to 2011. They are categorized by hospital spending intensity. A hierarchical linear regression model with a random-intercept model was used to analyze the relationship between end-of-life expenditure (dependent variable) with and without home-based hospice, and both patient-level and hospital-level characteristics. A total of 78,613 cancer decedents were identified in the NHIRD from 2009 to 2011. Of these decedents, 17,638, 43,286, and 17,689 were categorized by hospital spending intensity as high, moderate, and low, respectively. Decedents with home-based hospice care were associated with US$2452 less in expenditure per patient compared with those without home-based hospice care. The majority of savings occurred in the last 3 months of life. These savings with home-based hospice care were consistent in hospitals with different levels of spending intensity. Home-based hospice reduced one-fifth expenditure at the end of life of cancer decedents treated in hospitals with different spending intensity. 10. An Integrated Approach to Fatigue Life Prediction of Whole System for Offshore Platforms Institute of Scientific and Technical Information of China (English) 方华灿; 段梦兰; 许发彦; 吴永宁; 樊晓东 2001-01-01 The failure of one or even more components usually does not lead to the collapse of the whole structure. Most of theanalysis of fatigue is centered on only a single component which the researchers are interested in or much attentionshould be paid to. However, the collapse of a structure is the result of failure of a series of components in a specific orderor path. This paper proposes an integrated approach to fatigue life prediction of whole structural system for offshoreplatforms, mainly describing the basic principles and prediction method. A method is presented for determining the fail-ure path of the whole structure system and calculating the fatigue life in the determined failure path. The correspondingfinal collapse criteria for the whole structure system are discussed. A simple method of equivalent fatigue stress range cal-culation and a mathematical model of structural component fatigue life estimation in consideration of sea wave and seaice loads are provided. As an application of the proposed approach, a fixed production platform Bohai No. 8 is chosenfor the predication of fatigue life of the whole structure system by means of the software OSFAC developed based on thepresent methods. 11. Effects of hydrogen on fatigue life of Ti-4Al-2V titanium alloy Institute of Scientific and Technical Information of China (English) 何晓; 岳俊; 沈保罗; 曹建玲; 邱绍宇; 邹红 2003-01-01 Four hydrogen contents were employed to investigate the effects of hydrogen on fatigue life of Ti-4Al-2V titanium alloy by means of section-varied samples. Results reveal that the fatigue life of the materials with (116～280)×10-6 hydrogen is higher than that of natural hydrogen material provided that the fatigue load Δσ is over 550MPa. At higher Δσ, the content of hydrogen has small effects on fatigue life within (116-280)×10-6 hydrogen. For material containing 280×10-6 hydrogen, fatigue cracks tend to initiate at sample edges at higher load, in contrast, to initiate at sites of hydrides at lower load. The interstitial hydrogen atoms softening the persistent slip bands(PSB) and hydrides separating from the body become the cause of decrease in fatigue life. Hydrides resolved into the body is observed at lower Δσ for material with 280×10-6 hydrogen, which is the result of concentration of hydrogen atoms at crack tips and stress-induced re-precipitation of hydrides. 12. Numerical fatigue life assessment of cardiovascular stents: A two-scale plasticity-damage model Science.gov (United States) Santos, H. A. F. A.; Auricchio, F.; Conti, M. 2013-07-01 Cardiovascular disease has become a major global health care problem in the last decades. To tackle this problem, the use of cardiovascular stents has been considered a promising and effective approach. Numerical simulations to evaluate the in vivo behavior of stents are becoming more and more important to assess potential failures. As the material failure of a stent device has been often associated with fatigue issues, numerical approaches for fatigue life assessment of stents have gained special interest in the engineering community. Numerical fatigue life predictions can be used to modify the design and prevent failure without making and testing numerous physical devices, thus preventing from undesired fatigue failures. We present a numerical fatigue life model for the analysis of cardiovascular balloon-expandable stainless steel stents that can hopefully provide useful information either to be used for product improvement or for clinicians to make life-saving decisions. This model incorporates a two-scale continuum damage mechanics model and the so-called Soderberg fatigue failure criterion. We provide numerical results for both Palmaz-Schatz and Cypher stent designs and demonstrate that a good agreement is found between the numerical and the available experimental results. 13. Fatigue life estimation procedures for the endurance of a cardiac valve prosthesis: stress/life and damage-tolerant analyses. Science.gov (United States) Ritchie, R O; Lubock, P 1986-05-01 Projected fatigue life analyses are performed to estimate the endurance of a cardiac valve prosthesis under physiological environmental and mechanical conditions. The analyses are conducted using both the classical stress-strain/life and the fracture mechanics-based damage-tolerant approaches, and provide estimates of expected life in terms of initial flaw sizes which may pre-exist in the metal prior to the valve entering service. The damage-tolerant analysis further is supplemented by consideration of the question of "short cracks," which represents a developing area in metal fatigue research, not commonly applied to data in standard engineering design practice. 14. Fatigue in patients with neuromyelitis optica spectrum disorder and its impact on quality of life. Science.gov (United States) Seok, Jin Myoung; Choi, Misong; Cho, Eun Bin; Lee, Hye Lim; Kim, Byoung Joon; Lee, Kwang Ho; Song, Pamela; Joo, Eun Yeon; Min, Ju-Hong 2017-01-01 Fatigue is a prevalent symptom and major burden in neuroimmunological diseases. In neuromyelitis optica spectrum disorder (NMOSD), a severe autoimmune central nervous system (CNS) inflammatory disease with autoantibodies reactive to aquaporin-4, there are few reports about fatigue and quality of life (QOL). We aimed to evaluate the severity of fatigue and its relationship with QOL in patients with NMOSD. We prospectively studied patients with NMOSD who were in remission and seropositive for anti-aquaporin-4 antibody, and they were divided into 2 groups based on the presence of fatigue assessed using the Functional Assessment of Chronic Illness Therapy-fatigue score. Sleep quality, depression, pain, and QOL were also evaluated. A total of 35 patients were enrolled (mean age, 46.5 ± 14.1 years; female: male = 29:6), and the median Expanded Disability Status Scale (EDSS) score was 2.0 (range, 0 to 8.0). The patients with fatigue (N = 25, 71.4%) had poorer sleep quality and more severe depression than those without fatigue (p = 0.009 and p = 0.001). Both the physical and mental QOL scores were lower in patients with fatigue than in those without fatigue (p = 0.033 and p = 0.004). Multiple linear regression analyses showed that the degree of fatigue with EDSS score and pain were independent predictors of physical aspects of QOL (B = 0.382, p = 0.001), whereas depression was the only predictor of the mental components of QOL (B = -0.845, p = <0.001). Fatigue is a common symptom and an important predictor of QOL in patients with NMOSD. 15. Comparing Fatigue Life Estimations of Composite Wind Turbine Blades using different Fatigue Analysis Tools DEFF Research Database (Denmark) Ardila, Oscar Gerardo Castro; Lennie, Matthew; Branner, Kim; 2015-01-01 suggested by the IEC 61400-1 standard were studied employing different load time intervals and by using two novel fatigue tools called ALBdeS and BECAS+F. The aeroelastic loads were defined thought aeroelastic simulations performed with both FAST and HAWC2 tools. The stress spectra at each layer were... 16. Experimental Investigation on the Fatigue Life of Ti-6Al-4V Treated by Vibratory Stress Relief Directory of Open Access Journals (Sweden) Han-Jun Gao 2017-05-01 Full Text Available Vibratory stress relief (VSR is a highly efficient and low-energy consumption method to relieve and homogenize residual stresses in materials. Thus, the effect of VSR on the fatigue life should be determined. Standard fatigue specimens are fabricated to investigate the fatigue life of Ti-6Al-4V titanium alloy treated by VSR. The dynamic stresses generated under different VSR amplitudes are measured, and then the relationship between the dynamic stress and vibration amplitude is obtained. Different specimen groups are subjected to VSRs with different amplitudes and annealing treatment with typical process parameters. Residual stresses are measured to evaluate the stress relieving effects. Finally, the fatigue behavior under different states is determined by uniaxial tension–compression fatigue experiments. Results show that VSR and annealing treatment have negative effects on the fatigue life of Ti-6Al-4V. The fatigue life is decreased with the increase in VSR amplitude. When the VSR amplitude is less than 0.1 mm, the decrease in fatigue limit is less than 2%. Compared with specimens without VSR or annealing treatment, the fatigue limit of the specimens treated by VSR with 0.2 mm amplitude and annealing treatment decreases by 10.60% and 8.52%, respectively. Although the stress relieving effect is better, high amplitude VSR will lead to the decrease of Ti-6Al-4V fatigue life due to the defects generated during vibration. Low amplitude VSR can effectively relieve the stress with little decrease in fatigue life. 17. The effects of fibre architecture on fatigue life-time of composite materials Energy Technology Data Exchange (ETDEWEB) Zangenberg Hansen, J. 2013-09-15 Wind turbine rotor blades are among the largest composite structures manufactured of fibre reinforced polymer. During the service life of a wind turbine rotor blade, it is subjected to cyclic loading that potentially can lead to material failure, also known as fatigue. With reference to glass fibre reinforced composites used for the main laminate of a wind turbine rotor blade, the problem addressed in the present work is the effect of the fibre and fabric architecture on the fatigue life-time under tension-tension loading. Fatigue of composite materials has been a central research topic for the last decades; however, a clear answer to what causes the material to degrade, has not been given yet. Even for the simplest kind of fibre reinforced composites, the axially loaded unidirectional material, the fatigue failure modes are complex, and require advanced experimental techniques and characterisation methodologies in order to be assessed. Furthermore, numerical evaluation and predictions of the fatigue damage evolution are decisive in order to make future improvements. The present work is focused around two central themes: fibre architecture and fatigue failure. The fibre architecture is characterised using real material samples and numerical simulations. Experimental fatigue tests identify, quantify, and analyse the cause of failure. Different configurations of the fibre architecture are investigated in order to determine and understand the tension-tension fatigue failure mechanisms. A numerical study is used to examine the onset of fatigue failure. Topics treated include: experimental fatigue investigations, scanning electron microscopy, numerical simulations, advanced measurements techniques (micro computed tomography and thermovision), design of test specimens and preforms, and advanced materials characterisation. The results of the present work show that the fibre radii distribution has limited effect on the fibre architecture. This raises the question of which 18. Quality of life, fatigue, depression and cognitive impairment in Lyme neuroborreliosis. Science.gov (United States) Dersch, Rick; Sarnes, Antonia A; Maul, Monika; Hottenrott, Tilman; Baumgartner, Annette; Rauer, Sebastian; Stich, Oliver 2015-11-01 The prognosis and impact of residual symptoms on quality of life in patients with Lyme neuroborreliosis (LNB) is subject to debate. The aim of this study was to assess quality of life, fatigue, depression, cognitive impairment and verbal learning in patients with definite LNB and healthy controls in a case-control study. We retrospectively identified all patients diagnosed with definite LNB between 2003 and 2014 in our tertiary care center. Healthy controls were recruited from the same area. Patients and healthy controls were assessed for quality of life [Short Form (36) with subscores for physical and mental components (PCS, MCS)], fatigue (fatigue severity scale), depression (Beck depression inventory), verbal memory and learning and cognitive impairment (mini-mental state examination). 53 patients with definite LNB could be identified, of which 30 partook in the follow-up assessment. Estimates for quality of life, fatigue, depression, verbal memory and cognitive impairment did not differ statistically significantly between 30 patients with LNB and 35 healthy controls. Patients with residual symptoms had lower scores for quality of life (PCS) compared to patients without residual symptoms. Our results do not support the hypothesis that a considerable proportion of patients with antibiotically treated LNB develop a 'post Lyme syndrome' consisting of debilitating fatigue or cognitive impairment or have severe limitations of quality of life. However, some patients experience residual symptoms of LNB. 19. FATIGUE LIFE PREDICTION OF COMMERCIALLY PURE TITANIUM AFTER NITROGEN ION IMPLANTATION Directory of Open Access Journals (Sweden) Nurdin Ali 2013-06-01 Full Text Available Prediction of fatigue life has become an interesting issue in biomaterial engineering and design for reliability and quality purposes, particularly for biometallic material with modified surfaces. Commercially pure titanium (Cp-Ti implanted with nitrogen ions is a potential metallic biomaterial of the future. The effect of nitrogen ion implantation on fatigue behavior of Cp-Ti was investigated by means of axial loading conditions. The as-received and nitrogen-ion implanted specimens with the energy of 100 keV and dose of 2 × 1017 ions cm-2, were used to determine the fatigue properties and to predict the life cycle of the specimens. The effect of nitrogen ion implantation indicated revealed improved the tensile strength due to the formation of nitride phases, TiN and Ti2N. The fatigue strength of Cp-Ti and Nii-Ti was 250 and 260 MPa, respectively. The analytical results show good agreement with experimental results. 20. EVALUATION OF THE PROBABILITY DISTRIBUTION OF PITTING CORROSION FATIGUE LIFE IN AIRCRAFT MATERIALS Institute of Scientific and Technical Information of China (English) WANG Qingyuan (王清远); N.KAWAGOISHI; Q.CHEN; R.M.PIDAPARTI 2003-01-01 Corrosion and fatigue properties of aircraft materials are known to have a considerable scatter due to the random nature of materials,loading,and environmental conditions.A probabilistic approach for predicting the pitting corrosion fatigue life has been investigated which captures the effect of the interaction of the cyclic load and corrosive environment and all stages of the corrosion fatigue process (i.e.the pit nucleation and growth,pit-crack transition,short- and long-crack propagation).The probabilistic model investigated considers the uncertainties in the initial pit size,corrosion pitting current,and material properties due to the scatter found in the experimental data.Monte Carlo simulations were performed to define the failure probability distribution.Predicted cumulative distribution functions of fatigue life agreed reasonably well with the existing experimental data. 1. The effects of fibre architecture on fatigue life-time of composite materials DEFF Research Database (Denmark) Hansen, Jens Zangenberg; Østergaard, Rasmus Wind turbine rotor blades are among the largest composite structures manufactured of fibre reinforced polymer. During the service life of a wind turbine rotor blade, it is subjected to cyclic loading that potentially can lead to material failure, also known as fatigue. With reference to glass fibre...... reinforced composites used for the main laminate of a wind turbine rotor blade, the problem addressed in the present work is the effect of the fibre and fabric architecture on the fatigue life-time under tension-tension loading. Fatigue of composite materials has been a central research topic for the last...... decades; however, a clear answer to what causes the material to degrade, has not been given yet. Even for the simplest kind of fibre reinforced composites, the axially loaded unidirectional material, the fatigue failure modes are complex, and require advanced experimental techniques and characterisation... 2. Comparing Guidelines Concerning Construction of the S-N Curve within Limited Fatigue Life Range Directory of Open Access Journals (Sweden) Strzelecki Przemysław 2015-09-01 Full Text Available The article collates guidelines concerning experimental construction of the S-N fatigue curves within a limited fatigue life range. An attempt is made to compare these guidelines, based on experimental data recorded during rotating bending of a notched specimen made of 42CrMo4. The recorded differences in fatigue life values between the constructed curves reach the maximum of 12.2%. According to the above guidelines, the number of tests in particular test series varies from 6 to 28. Based on the performed analysis a conclusion was made that the increase in the number of tests leads to the increase of accuracy but, on the other hand, remarkably increases the time of the experiment and, consequently, its cost. In this context, it is the research worker who, taking into account a possible future use of the fatigue curve, should individually decide about its accuracy. 3. A comparison of some methods to estimate the fatigue life of plain dents Energy Technology Data Exchange (ETDEWEB) Martins, Ricardo R.; Noronha Junior, Dauro B. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil) 2009-12-19 This paper describes a method under development at PETROBRAS R and D Center (CENPES) to estimate the fatigue life of plain dents. This method uses the API Publication 1156 as a base to estimate the fatigue life of dome shaped plain dents and the Pipeline Defect Assessment Manual (PDAM) approach to take into account the uncertainty inherent in the fatigue phenomenon. CENPES method, an empirical and a semi-empirical method available in the literature were employed to estimate the fatigue lives of 10 plain dents specimens of Year 1 of an ongoing test program carried out by BMT Fleet Technology Limited, with the support of the Pipeline Research Council International (PRCI). The results obtained with the different methods are presented and compared. Furthermore some details are given on the numerical methodology proposed by PETROBRAS that have been used to describe the behavior of plain dents. (author) 4. Mathematical Model of Load Pass and Prediction of Fatigue Life on Bolt Threads with Reduced Lead Science.gov (United States) Asayama, Yukiteru A mathematical model is proposed in order to elucidate the mechanism that the fatigue strength of external threads increases by reducing the lead on a thread system such as a bolt and nut. The model is constructed from the concept that a local strain proportional to the reducing degree of the lead, although the local strain is at first produced in the bolt thread farthest from the bearing surface of the nut, is induced in each thread root with an increase of applied load. The fatigue life predicted from the mathematical model shows good agreement with the experimental fatigue life of cadmium-plated external threads with the reduced lead on the material having strength as high as 1270MPa. The model can provide useful suggestions for the design of fasteners for aerospace, which are required to satisfy severe requirements of fatigue strengths and dimensions. 5. Probabilistic fatigue life of balsa cored sandwich composites subjected to transverse shear DEFF Research Database (Denmark) Dimitrov, Nikolay Krasimirov; Berggreen, Christian 2015-01-01 be controlled to the same extent as an industrial manufacturing processes. The large variance in the probabilistic model for fatigue life is reflected in the corresponding calibrated partial safety factors, which are higher thanthe factors usually associated with synthetic materials such as fiber......A probabilistic fatigue life model for end-grain balsa cored sandwich composites subjectedto transverse shear is proposed. The model is calibrated to measured three-pointbending constant-amplitude fatigue test data using the maximum likelihood method. Some possible applications of the probabilistic...... model are obtaining characteristic S–Ncurves corresponding to a given survival probability, and calibrating partial safety factorsfor material fatigue. The latter is demonstrated by a calibration performed using reliability analysis with the first-order reliability method. The measured variance in balsa... 6. The effects of fibre architecture on fatigue life-time of composite materials DEFF Research Database (Denmark) Hansen, Jens Zangenberg; Østergaard, Rasmus Wind turbine rotor blades are among the largest composite structures manufactured of fibre reinforced polymer. During the service life of a wind turbine rotor blade, it is subjected to cyclic loading that potentially can lead to material failure, also known as fatigue. With reference to glass fibre...... reinforced composites used for the main laminate of a wind turbine rotor blade, the problem addressed in the present work is the effect of the fibre and fabric architecture on the fatigue life-time under tension-tension loading. Fatigue of composite materials has been a central research topic for the last...... decades; however, a clear answer to what causes the material to degrade, has not been given yet. Even for the simplest kind of fibre reinforced composites, the axially loaded unidirectional material, the fatigue failure modes are complex, and require advanced experimental techniques and characterisation... 7. High-cycle Fatigue Life Extension of Glass Fiber/Polymer Composites with Carbon Nanotubes Institute of Scientific and Technical Information of China (English) Christopher S Grimmer; C K H Dharan 2009-01-01 The present work shows that the addition of small volume fractions of multi-walled carbon nanotubes (CNTs) to the matrix results in a significant increase in the high-cycle fatigue life. It is proposed that carbon nanotubes tend to inhibit the formation of large cracks by nucleating nano-scale damage zones. In addition, the contribution to energy absorption from the fracture of nanotubes bridging across nano-scale cracks and from nanotube pull-out from the matrix are mechanisms that can improve the fatigue life. An energy-based model was proposed to estimate the additional strain energy absorbed in fatigue. The distributed nanotubes in the matrix appear to both distribute damage as well as inhibit damage propagation resulting in an overall improvement in the fatigue strength of glass fiber composites. 8. Fatigue Reliability Assessment of Steel Member Using Probabilistic Stress-Life Method Directory of Open Access Journals (Sweden) Dae-Hung Kang 2012-01-01 Full Text Available The fatigue reliability of a steel member in a bridge is estimated by using the probabilistic stress-life method. The stress history of a member is defined as the loading block when a truck passes over a bridge, and the stress range frequency distribution of the stress history is obtained by a stress range frequency analysis. A probabilistic method is applied to the stress range frequency distribution, and the parameters of the probability distribution for the stress range frequency distribution are used in a numerical simulation. To obtain the probability of failure of a member under a loading block, Monte Carlo simulation is performed in conjunction with Miner's rule, the modified Miner's rule, and Haibach's rule for fatigue damage evaluation. Through these analyses procedures, we obtain an evaluation method for fatigue reliability that can predict the block number of the failure load and residual fatigue life. 9. Probabilistic Fatigue Life Prediction of Bridge Cables Based on Multiscaling and Mesoscopic Fracture Mechanics Directory of Open Access Journals (Sweden) Zhongxiang Liu 2016-04-01 Full Text Available Fatigue fracture of bridge stay-cables is usually a multiscale process as the crack grows from micro-scale to macro-scale. Such a process, however, is highly uncertain. In order to make a rational prediction of the residual life of bridge cables, a probabilistic fatigue approach is proposed, based on a comprehensive vehicle load model, finite element analysis and multiscaling and mesoscopic fracture mechanics. Uncertainties in both material properties and external loads are considered. The proposed method is demonstrated through the fatigue life prediction of cables of the Runyang Cable-Stayed Bridge in China, and it is found that cables along the bridge spans may have significantly different fatigue lives, and due to the variability, some of them may have shorter lives than those as expected from the design. 10. Structural strength analysis and fatigue life prediction of traction converter box in high-speed EMU Science.gov (United States) Tan, Qin; Li, Qiang 2017-01-01 The method of building the FEA model of traction converter box in high-speed EMU and analyzing the static strength and fatigue strength of traction converter box based on IEC 61373-2010 and EN 12663 standards is presented in this paper. The load-stress correlation coefficients of weak points is obtained by FEA model, applied to transfer the load history of traction converter box to stress history of each point. The fatigue damage is calculated based on Miner's rule and the fatigue life of traction converter box is predicted. According to study, the structural strength of traction converter box meets design requirements. 11. A method for calculation of finite fatigue life under multiaxial loading in high-cycle domain Directory of Open Access Journals (Sweden) M. Malnati 2014-04-01 Full Text Available A method for fatigue life assessment in high-cycle domain under multiaxial loading is presented in this paper. This approach allows fatigue assessment under any kind of load history, without limitations. The methodology lies on the construction - at a macroscopic level - of an “indicator” in the form of a set of cycles, representing plasticity that can arise at mesoscopic level throughout fatigue process. During the advancement of the loading history new cycles are created and a continuous evaluation of the damage is made. 12. Fatigue Life of High Performance Grout for Wind Turbine Grouted Connection in Wet or Dry Environment DEFF Research Database (Denmark) Sørensen, Eigil V.; Westhof, Luc; Yde, Elo; Grouted connections of monopile supported offshore wind turbine structures are subjected to loads leading to very high oscillating service stresses in the grout material. The fatigue capacity of a high performance cement based grout was tested by dynamic compressive loading of cylindrical specimens...... at varying levels of cyclic frequency and load. The fatigue tests were performed in two series: one with the specimens in air and one with the specimens submerged in water during the test. The fatigue life of the grout, in terms of the number of cycles to failure, was found to be significantly shorter when...... tested in water than when tested in air.... 13. High compressive pre-strains reduce the bending fatigue life of nitinol wire. Science.gov (United States) Gupta, Shikha; Pelton, Alan R; Weaver, Jason D; Gong, Xiao-Yan; Nagaraja, Srinidhi 2015-04-01 Prior to implantation, Nitinol-based transcatheter endovascular devices are subject to a complex thermo-mechanical pre-strain associated with constraint onto a delivery catheter, device sterilization, and final deployment. Though such large thermo-mechanical excursions are known to impact the microstructural and mechanical properties of Nitinol, their effect on fatigue properties is still not well understood. The present study investigated the effects of large thermo-mechanical pre-strains on the fatigue of pseudoelastic Nitinol wire using fully reversed rotary bend fatigue (RBF) experiments. Electropolished Nitinol wires were subjected to a 0%, 8% or 10% bending pre-strain and RBF testing at 0.3-1.5% strain amplitudes for up to 10(8) cycles. The imposition of 8% or 10% bending pre-strain resulted in residual set in the wire. Large pre-strains also significantly reduced the fatigue life of Nitinol wires below 0.8% strain amplitude. While 0% and 8% pre-strain wires exhibited distinct low-cycle and high-cycle fatigue regions, reaching run out at 10(8) cycles at 0.6% and 0.4% strain amplitude, respectively, 10% pre-strain wires continued to fracture at less than 10(5) cycles, even at 0.3% strain amplitude. Furthermore, over 70% fatigue cracks were found to initiate on the compressive pre-strain surface in pre-strained wires. In light of the texture-dependent tension-compression asymmetry in Nitinol, this reduction in fatigue life and preferential crack initiation in pre-strained wires is thought to be attributed to compressive pre-strain-induced plasticity and tensile residual stresses as well as the formation of martensite variants. Despite differences in fatigue life, SEM revealed that the size, shape and morphology of the fatigue fracture surfaces were comparable across the pre-strain levels. Further, the mechanisms underlying fatigue were found to be similar; despite large differences in cycles to failure across strain amplitudes and pre-strain levels, cracks 14. Mechanical strength, fatigue life, and failure analysis of two prototypes and five conventional tibial locking screws. Science.gov (United States) Hou, Sheng-Mou; Wang, Jaw-Lin; Lin, Jinn 2002-01-01 To investigate the effects of the design and microstructure on the mechanical strength of tibial locking devices. The mechanical strength of two prototypes of specially developed locking devices (a both-ends-threaded screw and an unthreaded bolt) was tested and compared with that of five types of commercially available tibial locking screws (Synthes, Howmedica, Richards, Osteo AG, and Zimmer) with similar dimensions. The devices were inserted into a polyethylene tube and loaded at their midpoint by a materials testing machine to simulate a three-point bending test. Single-loading yielding strength and cyclic-loading fatigue life were then measured. Failure analysis of the fractured screws was performed to investigate the microstructure and potential causes of the fatigue fracture. Test results showed that both yielding strength and fatigue life were closely related to the section modulus of the inner diameter of screws. Among the threaded screws, the both-ends-threaded screws had a higher yielding strength and longer fatigue life than the Osteo AG, Howmedica, Richards, and Zimmer screws. The unthreaded bolts had a lower yielding strength than Synthes screws, but they demonstrated the longest fatigue life among all. In failure analysis of broken screws, no metallurgical or manufacturing defects were found except for surface microimperfections. The implants investigated in this study are manufactured with high-quality materials and manufacturing processes. The main cause of hardware failure was mechanical overloading. The five commercially used tibial locking screws had a relatively short fatigue life under high loading. Removing the screw threads might substantially increase the fatigue life of the locking devices. In unthreaded bolts, this increase might be tenfold to a hundredfold. 15. Anisotropic Elastoplastic Damage Mechanics Method to Predict Fatigue Life of the Structure OpenAIRE Hualiang Wan; Qizhi Wang; Zheng Zhang 2016-01-01 New damage mechanics method is proposed to predict the low-cycle fatigue life of metallic structures under multiaxial loading. The microstructure mechanical model is proposed to simulate anisotropic elastoplastic damage evolution. As the micromodel depends on few material parameters, the present method is very concise and suitable for engineering application. The material parameters in damage evolution equation are determined by fatigue experimental data of standard specimens. By employing fu... 16. Evaluation of creep-fatigue life-prediction models for the solar central receiver Science.gov (United States) Hyzak, J. M.; Hughes, D. A. 1981-09-01 The applicability of several creep fatigue models to life prediction of boiler tubes in a solar central receiver (SCR) was evaluated. The SCR boiler tubes will experience compressive strain dwell loading with hold times up to 6 to 8 hours at temperatures where time dependent deformation will occur. The evaluation criteria include the ability of the model to account for mean stress effects and to be practical in the long life, small strain range regime. A correlation between maximum tensile stress and fatigue life is presented. Using this correlation, compressive dwell behavior is predicted based on continuous cycling data. The limits of this predictive scheme are addressed. 17. FATIGUE LIFE PREDICTION OF CRANKSHAFT MADE OF MATERIAL 48MnV BASED ON FATIGUE TESTS,DYNAMIC SIMULATION AND FEA Institute of Scientific and Technical Information of China (English) ZHANG Guoqing; PU Gengqiang; WANG Chengtao 2006-01-01 S-N curve and fatigue parameters of 48MnV are obtained using small sample tests and staircase or up and down method, which paves the way for predicting fatigue life of crankshaft made of 48MnV. The fatigue life of the crankshaft of a six-cylinder engine is calculated using different damage models such as S-N method, normal strain approach, Smoth-Watson-Topper (SWT)-Bannantine approach, shear strain approach, and Fatemi-Socie method based on dynamic simulation and finite element analysis (FEA) of crankshaft. The results indicate that the traditional calculation is conservative and the residual fatigue life of crankshaft is sufficient to maintain next life cycle if the crankshaft is remanufactured after its end of life. 18. Probabilistic Fatigue Life Prediction of Turbine Disc Considering Model Parameter Uncertainty Science.gov (United States) He, Liping; Yu, Le; Zhu, Shun-Peng; Ding, Liangliang; Huang, Hong-Zhong 2016-06-01 Aiming to improve the predictive ability of Walker model for fatigue life prediction and taking the turbine disc alloy GH4133 as the application example, this paper investigates a new approach for probabilistic fatigue life prediction when considering parameter uncertainty inherent in the life prediction model. Firstly, experimental data are used to update the model parameters using Bayes' theorem, so as to obtain the posterior probability distribution functions of two parameters of the Walker model, as well to achieve the probabilistic life prediction model for turbine disc. During the updating process, Markov Chain Monte Carlo (MCMC) technique is used to generate samples of the given distribution and estimating the parameters distinctly. After that, the turbine disc life is predicted using the probabilistic Walker model based on Monte Carlo simulation technique. The experimental results indicate that: (1) after using the small sample test data obtained from turbine disc, parameter uncertainty of the Walker model can be quantified and the corresponding probabilistic model for fatigue life prediction can be established using Bayes' theorem; (2) there exists obvious dispersion of life data for turbine disc when predicting fatigue life in practical engineering application. 19. The Prediction of Fatigue Life Based on Four Point Bending Test NARCIS (Netherlands) Pramesti, F.P.; Molenaar, A.A.A.; Van de Ven, M.F.C. 2013-01-01 To be able to devise optimum strategies for maintenance and rehabilitation, it is essential to formulate an accurate prediction of pavement life and its maintenance needs. One of the pavement life prediction methods is based on the pavement's capability to sustain fatigue. If it were possible to hav 20. Detection and Influence of Shrinkage Pores and Nonmetallic Inclusions on Fatigue Life of Cast Aluminum Alloys Science.gov (United States) Tijani, Yakub; Heinrietz, André; Stets, Wolfram; Voigt, Patrick 2013-12-01 In the current study, test bars of cast aluminum alloys EN AC-AlSi8Cu3 and EN AC-AlSi7Mg0.3 were produced with a defined amounts of shrinkage pores and oxides. For this purpose, a permanent mold with heating and cooling devices for the generation of pores was constructed. The oxides were produced by contaminating the melt. The specimens and their corresponding defect distributions were examined and quantified by X-ray computer tomography (CT) and quantitative metallography, respectively. A special test algorithm for the simultaneous image analyses of pores and oxides was developed. Fatigue tests were conducted on the defective samples. It was found that the presence of shrinkage pores lowers the fatigue strength, and only few oxide inclusions were found to initiate fatigue cracks when shrinkage pores are present. The results show that the pore volume is not sufficient to characterize the influence of shrinkage pores on fatigue life. A parametric model for the calculation of fatigue life based on the pore parameters obtained from CT scans was implemented. The model accounts for the combined impact of pore location, size, and shape on fatigue life reduction. 1. Effect of V Notch Shape on Fatigue Life in Steel Beam Made of AISI 1037 Directory of Open Access Journals (Sweden) Qasim Bader 2014-04-01 Full Text Available The present work encompasses effect of V notch shape with various geometries and dimensions on fatigue life behavior in steel beam made of Medium Carbon Steel AISI 1037 which has a wide application in industry. Fatigue life of notched specimens is calculated using the fatigue life obtained from the experiments for smooth specimens (reference and by use Numerical method (FEA.The fatigue experiments were carried out at room temperature, applying a fully reversed cyclic load with the frequency of (50Hz and mean stress equal to zero (R= -1, on a cantilever rotating-bending fatigue testing machine. The stress ratio was kept constant throughout the experiment. Different instruments have been used in this investigation like Chemical composition analyzer type (Spectromax ,Tensile universal testing machine type (WDW-100E ,Hardness tester type (HSV- 1000 , Fatigue testing machine model Gunt WP 140, Optical Light Microscope (OLM and Scanning Electron Microscope (SEM were employed to examine the fracture features . The results show that there is acceptable error between experimental and numerical works . 2. Fatigue life estimation for different notched specimens based on the volumetric approach Directory of Open Access Journals (Sweden) Esmaeili F. 2010-06-01 Full Text Available In this paper, the effects of notch radius for different notched specimens has been studied on the values of stress concentration factor, notch strength reduction factor, and fatigue life duration of the specimens. The material which has been selected for this investigation is Al 2024T3 . Volumetric approach has been applied to obtain the values of notch strength reduction factor and results have been compared with those obtained from the Neuber and Peterson methods. Load controlled fatigue tests of mentioned specimens have been conducted on the 250kN servo-hydraulic Zwick/Amsler fatigue testing machine with the frequency of 10Hz. The fatigue lives of the specimens have also been predicted based on the available smooth S-N curve of Al2024-T3 and also the amounts of notch strength reduction factor which have been obtained from volumetric, Neuber and Peterson methods. The values of stress and strain around the notch roots are required to predict the fatigue life of notched specimens, so Ansys finite element code has been used and non-linear analyses have been performed to obtain the stress and strain distributions around the notches. The plastic deformations of the material have been simulated using multi-linear kinematic hardening and cyclic stress-strain relation. The work here shows that the volumetric approach does a very good job for predicting the fatigue life of the notched specimens. 3. Evaluation of Fatigue Life Reliability of Steering Knuckle Using Pearson Parametric Distribution Model Directory of Open Access Journals (Sweden) E. A. Azrulhisham 2010-01-01 Full Text Available Steering module is a part of automotive suspension system which provides a means for an accurate vehicle placement and stability control. Components such as steering knuckle are subjected to fatigue failures due to cyclic loads arising from various driving conditions. This paper intends to give a description of a method used in the fatigue life reliability evaluation of the knuckle used in a passenger car steering system. An accurate representation of Belgian pave service loads in terms of response-time history signal was obtained from accredited test track using road load data acquisition. The acquired service load data was replicated on durability test rig and the SN method was used to estimate the fatigue life. A Pearson system was developed to evaluate the predicted fatigue life reliability by considering the variations in material properties. Considering random loads experiences by the steering knuckle, it is found that shortest life appears to be in the vertical load direction with the lowest fatigue life reliability between 14000–16000 cycles. Taking into account the inconsistency of the material properties, the proposed method is capable of providing the probability of failure of mass-produced parts. 4. Prevalence of fatigue in patients with multiple sclerosis and its effect on the quality of life Directory of Open Access Journals (Sweden) Karthik Nagaraj 2013-01-01 Full Text Available Objective: This prospective study was carried out to observe the prevalence of fatigue in patients with multiple sclerosis (MS and its effect on quality-of-life (QoL. Study Design and Setting: Prospective observational study in a University Tertiary Research Hospital in India. Patients and Methods: A total of 31 patients (25 females with definite MS according to McDonald′s criteria presented in out-patient/admitted in the Department of Neurology (between February 2010 and December 2011 were included in the study. Disease severity was evaluated using the Kurtzke′s expanded disability status scale (EDSS. Fatigue was assessed using Krupp′s fatigue severity scale (FSS. QoL was assessed by the World Health Organization QoL-BREF questionnaire. Results: The mean age of patients was 30.1 ± 9.1 years. The mean age at first symptom was 25.23 ± 6.4 years. The mean number of relapses was 4.7 ± 3.6 in the patients. The mean duration of illness was 4.9 ± 4.4 years. The mean EDSS score was 3.5 ± 2.2. Mean fatigue score was 38.7 ± 18.5 (cut-off value 36 in FSS. The prevalence of fatigue in patients with MS was 58.1% (18/31. MS patients with fatigue were significantly more impaired (P < 0.05 on all QoL domains (i.e., physical, psychosocial, social, and environment than MS patients without fatigue. Conclusion: Prevalence of fatigue was found to be high in the MS patients in the study. All four domains of QoL were significantly more impaired in the group with fatigue than in those without fatigue. 5. Fatigue and Quality of Life of Women Undergoing Chemotherapy or Radiotherapy for Breast Cancer Institute of Scientific and Technical Information of China (English) Winnie K.W.So; Gene Marsh; W.M.Ling; F.E Leung; Joe C.K.Lo; Maggie Yeung; George K.H.Li 2009-01-01 OBJECTIVE To examine fatigue and quality of life (QOL) in breast cancer patients undergoing chemotherapy or radiotherapy.METHODS A self-report survey derived from the Chinese version of Brief Fatigue Inventory, the Functional Assessment of Chronic Illness Therapy for Breast Cancer, and the Medical Outcomes Study Social Support Survey. Descriptive statistics was used to examine the intensity of fatigue and the prevalence of severe fatigue. Multivariate analysis of variance was used to determine factors that affect the five domains of QOL among the participants.RESULTS The majority of the participants (n = 261) perceived a mild level of fatigue, but 35.6% of them suffered severe fatigue. Fatigue had a significantly negative association with all domains of QOL except social/family wellbeing. The participants who were receiving chemotherapy, undergoing curative treatment and having inadequate social support were more likely to have poorer QOL in all five domains (after adjustment for age).CONCLUSION Although the majority of the participants experienced a mild level of fatigue, there was a substantial group of breast cancer patients who perceived their fatigue as severe. The findings of this study showed that fatigue had a detrimental effect on the various aspects of the participants'QOL. Demographic and clinical characteristics of breast cancer patients who were at risk of getting poorer QOL were identified. The results of the study demonstrate that we should enhance healthcare professionals' awareness of the importance of symptom assessment, and provide them with information for planning effective symptom-management strategies among this study population. 6. Prevalence of fatigue in patients with multiple sclerosis and its effect on the quality of life. Science.gov (United States) Nagaraj, Karthik; Taly, Arun B; Gupta, Anupam; Prasad, Chandrajit; Christopher, Rita 2013-07-01 This prospective study was carried out to observe the prevalence of fatigue in patients with multiple sclerosis (MS) and its effect on quality-of-life (QoL). Prospective observational study in a University Tertiary Research Hospital in India. A total of 31 patients (25 females) with definite MS according to McDonald's criteria presented in out-patient/admitted in the Department of Neurology (between February 2010 and December 2011) were included in the study. Disease severity was evaluated using the Kurtzke's expanded disability status scale (EDSS). Fatigue was assessed using Krupp's fatigue severity scale (FSS). QoL was assessed by the World Health Organization QoL-BREF questionnaire. The mean age of patients was 30.1 ± 9.1 years. The mean age at first symptom was 25.23 ± 6.4 years. The mean number of relapses was 4.7 ± 3.6 in the patients. The mean duration of illness was 4.9 ± 4.4 years. The mean EDSS score was 3.5 ± 2.2. Mean fatigue score was 38.7 ± 18.5 (cut-off value 36 in FSS). The prevalence of fatigue in patients with MS was 58.1% (18/31). MS patients with fatigue were significantly more impaired (P QoL domains (i.e., physical, psychosocial, social, and environment) than MS patients without fatigue. Prevalence of fatigue was found to be high in the MS patients in the study. All four domains of QoL were significantly more impaired in the group with fatigue than in those without fatigue. 7. An Experimental Investigation of the Effects of Vacuum Environment on the Fatigue Life, Fatigue-Crack-Growth Behavior, and Fracture Toughness of 7075-T6 Aluminum Alloy. Ph.D. Thesis - North Carolina State Univ. Science.gov (United States) Hudson, C. M. 1972-01-01 Axial load fatigue life, fatigue-crack propagation, and fracture toughness tests were conducted on 0.090-inch thick specimens made of 7075-T6 aluminum alloy. The fatigue life and fatigue-crack propagation experiments were conducted at a stress ratio of 0.02. Maximum stresses ranged from 33 to 60 ksi in the fatigue life experiments, and from 10 to 40 ksi in the fatigue-crack propagation experiments, and fatigue life experiments were conducted at gas pressures of 760, 0.5, 0.05, and 0.00000005 torr. Fatigue-crack-growth and fracture toughness experiments were conducted at gas pressures of 760 and 5 x 10 to the minus 8th power torr. Residual stress measurements were made on selected fatigue life specimens to determine the effect of such stresses on fatigue life. Analysis of the results from the fatigue life experiments indicated that fatigue life progressively increased as the gas pressure decreased. Analysis of the results from the fatigue-crack-growth experiments indicates that at low values of stress-intensity range, the fatigue crack growth rates were approximately twice as high in air as in vacuum. Fracture toughness data showed there was essentially no difference in the fracture toughness of 7075-T6 in vacuum and in air. 8. Fatigue in Patients With Advanced Terminal Cancer Correlates With Inflammation, Poor Quality of Life and Sleep, and Anxiety/Depression. Science.gov (United States) Rodrigues, Alex Rua; Trufelli, Damila Cristina; Fonseca, Fernando; de Paula, Larissa Carvalho; Giglio, Auro Del 2016-12-01 To assess which laboratory and clinical factors are associated with fatigue in patients with terminal cancer. We evaluated 51 patients with advanced incurable solid tumors using the Chalder Fatigue Questionnaire (CFQ) and the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) scale for fatigue; the Pittsburgh Sleep Quality Index (PSQI-BR) for sleep quality; the Hospital Anxiety and Depression Scale (HADS) for anxiety and depression; the European Organization for Research and Treatment of Cancer (EORTC) Core Quality of Life Questionnaire, Version 3.0 (QLQ C-30); and Functional Assessment of Cancer Therapy (FACT) for quality of life. We also analyzed several inflammatory markers and the modified Glasgow prognostic score (mGPS). We observed severe fatigue in 19 (38%) patients (FACIT-F score >36). There was a significant correlation between fatigue as evaluated by the CFQ and quality of sleep and between the CFQ mental fatigue subscale scores and TNF-α level. When fatigue was evaluated using the FACIT-F scale, we observed a significant association between fatigue and anxiety/depression, quality of sleep, mGPS, and hemoglobin levels. Fatigue measured both with the CFQ and FACIT-F scale correlated with poor quality of life according to the EORTC QLQ C-30. In patients with advanced cancer, fatigue is a common symptom associated with the presence of inflammation, poor quality of sleep, depression/anxiety, and poor quality of life. © The Author(s) 2015. 9. Determinants of End-of-Life Expenditures in Patients with Oral Cancer in Taiwan: A Population-Based Study. Directory of Open Access Journals (Sweden) Ching-Chih Lee Full Text Available To investigate the association of basic demographic data, socioeconomic status, medical services, and hospital characteristics with end-of-life expenditure in patients with oral cancer in Taiwan who died between 2009 to 2011.This nationwide population-based, retrospective cohort study identified 5,386 patients who died from oral cancer. We evaluated medical cost in the last month of life by universal health insurance. The impact of each variable on the end-of-life expenditure was examined by hierarchical generalized linear model (HGLM using a hospital-level random-intercept model.The mean medical cost in the last six months of life was$2,611±3,329 (U.S. dollars. In HGLM using a random-intercept model, we found that patients younger than 65 years had an additional cost of $819 over those aged ≥65 years. Patients who had a high Charlson Comorbidity Index Score (CCIS had an additional$616 cost over those with a low CCIS. Those who survived post-diagnosis less than 6 months had an additional $659 in expenses over those who survived more than 24 months. Medical cost was$249 more for patients who had medium to high individual SES, and $319 more for those who were treated by non-oncologists.This study provides useful information for decision makers in understanding end-of-life expenditure in oral cancer. We found significantly increased end-of-life expenditure in patients if they were younger than 65 years or treated by non-oncologists, or had high CCIS, medium to high individual SES, and survival of less than 6 months after diagnosis. 10. Development of Fatigue Life Improvement Technology of Butt Joints Using Friction Stir Processing Directory of Open Access Journals (Sweden) Jeong-Ung Park 2014-03-01 Full Text Available Burr grinding, tungsten inert gas (TIG dressing, ultrasonic impact treatment, and peening are used to improve fatigue life in steel structures. These methods improve the fatigue life of weld joints by hardening the weld toe, improving the bead shape, or causing compressive residual stress. This study proposes a new postweld treatment method improving the weld bead shape and metal structure at the welding zone using friction stir processing (FSP to enhance fatigue life. For that, a pin-shaped tool and processing condition employing FSP has been established through experiment. Experimental results revealed that fatigue life improves by around 42% compared to as-welded fatigue specimens by reducing the stress concentration at the weld toe and generating a metal structure finer than that of flux-cored arc welding (FCAW. Hot-spot stress, structural stress, and simplified calculation methods cannot predict the accurate stress at the weld toe in case the weld toe has a smooth curvature as in the case of the FSP specimen. On the contrary, a finite element calculation could reasonably predict the stress concentration factor for the FSP specimen because it considers not only the bead profile but also the weld toe profile. 11. Fatigue and depression in multiple sclerosis: Correlation with quality of life Directory of Open Access Journals (Sweden) Miletić Svetlana 2011-01-01 Full Text Available The aim of this work was to examine the relationship between fatigue and depression, common features of multiple sclerosis (MS, and the quality of life (QOL. The study was comprised of 120 patients with clinical manifestations of definite MS. Relapsing-remitting MS was present in 76.7% patients and secondary progressive MS was present in 23.3% patients. Mean disease duration was 8.1 ± 5.6 years and the mean Expanded Disability Status Score (EDSS was 3.5 ± 1.8 (range 1-8. Fatigue was measured with the Fatigue Severity Scale (FSS, depression was measured by the Beck Depression Inventory (BDI and QOL was assessed using the health-related quality of life questionnaire SF-36. We observed that the global FSS score was 4.6 ± 1.8 (range 1-7 and BDI was 10.7 ± 10.3 (range 0-39. The FSS significantly and positively correlated with the BDI scores (r = 0.572; p = 0.000. The severity of fatigue had a significant impact on the quality of life (r = -0.743; p = 0.000, in particular on mental health (r = -0.749; p = 0.000. We observed a significant correlation between the severity of depression and impaired quality of life (r = -0.684; p = 0.000. This study shows that fatigue and depression are associated with impaired QOL in MS. 12. SOURCES OF DIFFERENCES IN CALCULATIONS AND EXPERIMENTAL TEST RESULTS OF FATIGUE LIFE OF STRUCTURAL ELEMENTS Directory of Open Access Journals (Sweden) Józef SZALA 2014-06-01 Full Text Available Calculation results are the base for evaluation of fatigue life of structural elements during machine design processes. It results from the fact that there are no material objects in the phase of existence of a product. Reliability of tests results is an essential element in the calculation fatigue life evaluation method and it can be evaluated by comparison of the results with experimental ones. In the paper there was performed an analysis of the chosen factors essentially influencing conformity of calculation results and experimental test ones connected with basic elements of a calculation algorithm including: - elaboration and analysis of service loadings of a structural element, - determination and analysis of cyclic properties of structural elements, - selection of fatigue damage accumulation hypothesis being a description of fatigue life processes. The mentioned analysis was illustrated with examples of fatigue life tests performed in the Machine Design Department of the University of Technology and Agriculture within the research grant no. 2221/B/T02/2010/39 financed by The Ministry of Science and Higher Education and National Science Centre. 13. Self-reported fatigue and physical function in late mid-life DEFF Research Database (Denmark) Boter, Han; Mänty, Minna; Hansen, Åse Marie 2014-01-01 population cohort (n = 4,964; age 49-63 years). Methods: Self-reported fatigue was measured using the MFI-20 comprising: general fatigue, physical fatigue, reduced activity, reduced motivation, and mental fatigue. Handgrip strength and chair rise tests were used as measures of physical function. Multiple.......001), general fatigue (adjusted OR 0.72 (0.62-0.84); p ≤ 0.001), reduced activity (adjusted OR 0.79 (0.70-0.90); p ≤ 0.001) and reduced motivation (adjusted OR 0.84 (0.74-0.95); p ≤ 0.01), but not with mental fatigue. Subgroup analyses for sex did not show statistically significant different associations......Objective: To determine the association between the 5 subscales of the Multidimensional Fatigue Inventory (MFI-20) and physical function in late mid-life. Design: Cross-sectional study. Subjects: A population-based sample of adults who participated in the Copenhagen Aging and Midlife Biobank... 14. Uphill both ways: Fatigue and quality of life in valley fever. Science.gov (United States) Garrett, Ashley L; Chang, Yu-Hui H; Ganley, Kathleen; Blair, Janis E 2016-03-01 Primary pulmonary coccidioidomycosis is characterized by prolonged respiratory and systemic symptoms and fatigue. We prospectively administered the fatigue severity scale (FSS) and Short Form-36 Health Status Questionnaire (SF-36) to patients with proven or probable primary pulmonary coccidioidomycosis to quantify disease effect on quality of life (QOL). The 24-week observational study did not specify whether antifungal treatment would be provided; the treating physician made treatment decisions. FSS and SF-36 were completed at 4-week intervals. Thirty-six patients participated, of whom 20 received antifungal treatment. At onset of coccidioidal illness, mean FSS score was higher (ie, more fatigue) in the treatment group. However, in early illness, both groups had higher fatigue levels than reference populations with other diseases (eg, multiple sclerosis). FSS scores gradually improved, and scores in each group were below the severe fatigue level at week 12 and week 16 in the nontreatment and treatment groups, respectively. By week 24, mean FSS score of the nontreatment group equaled the general population. SF-36 component and profile scores were lower (with more symptoms) in the treatment group at each time point than the nontreatment group; both groups showed similar improvement. Mental and emotional health SF-36 scores were not as severely affected as physical scores. Most patients reached a physical functioning level similar to the general population at week 12. Pulmonary coccidioidomycosis causes severe fatigue and substantially affects physical abilities. Fatigue was found to be prolonged, with gradual improvement in QOL, regardless of antifungal administration. 15. Effects of sodium tartrate anodizing on fatigue life of TA15 titanium alloy Directory of Open Access Journals (Sweden) Fu Chunjuan 2015-08-01 Full Text Available Anodizing is always used as an effective surface modification method to improve the corrosion resistance and wear resistance of titanium alloy. The sodium tartrate anodizing is a new kind of environmental anodizing method. In this work, the effects of sodium tartrate anodizing on mechanical property were studied. The oxide film was performed on the TA15 titanium alloy using sodium tartrate as the film former. The effects of this anodizing and the traditional acid anodizing on the fatigue life of TA15 alloy were compared. The results show that the sodium tartrate anodizing just caused a slight increase of hydrogen content in the alloy, and had a slight effect on the fatigue life. While, the traditional acid anodizing caused a significant increase of hydrogen content in the substrate and reduced the fatigue life of the alloy significantly. 16. Fatigue assessment and its impact in the quality of life of patients with ankylosing spondylitis. Science.gov (United States) Schneeberger, Emilce Edith; Marengo, María Florencia; Dal Pra, Fernando; Maldonado Cocco, José Antonio; Citera, Gustavo 2015-03-01 The most frequently reported symptoms by patients with ankylosing spondylitis (AS) are pain, stiffness, and fatigue. Previous studies have estimated a 63% prevalence of fatigue in AS, with a low correlation of fatigue with pain and functional capacity. The objective of this study is to assess fatigue prevalence in AS patients and establish the main associated factors. A case-control study including AS patients according to New York modified criteria was carried out. The control group included individuals of the general population without rheumatic conditions, matched by gender, age, and socioeconomic level. Disease-related variables were recorded. Functional capacity, disease activity, and quality of life were assessed using Bath Ankylosing Spondylitis Funcional Index (BASFI), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), and ankylosing spondylitis quality of life (ASQoL). CES-D questionnaire was used to evaluate depression and fatigue severity scale (FSS) to evaluate fatigue. Sixty-four consecutive AS patients and 95 controls were included. Patients' median age was 44 years (interquartile range (IQR), 33.25-53), 89.1% were male, and had a median disease duration of 17 years (IQR, 10.3-25). Fatigue prevalence in AS was 73.4% compared to 30.5% in the control group (p < 0.001; OR, 2.08 (95% CI, 1.53-2.83)). Furthermore, fatigue in AS correlated with ASQoL (r = 0.65), BASFI (r = 0.52), BASDAI (r = 0.52), and depression (r = 0.51), whereas no correlation with age or disease duration was found. In the linear regression analysis using fatigue as the dependent variable, depression was the only associated variable (p = 0.01). No association with age, gender, disease duration, BASDAI, BASFI, or presence of comorbidities was found. Finally, BASDAI fatigue question correlated with the FSS (r = 0.55). Fatigue was significantly more prevalent in AS than in healthy controls. The main determinant factor of fatigue was the presence of 17. PSYCHOMETRIC PROPERTY OF FATIGUE SEVERITY SCALE AND CORRELATION WITH DEPRESSION AND QUALITY OF LIFE IN CIRRHOTICS Directory of Open Access Journals (Sweden) Danusa ROSSI 2017-10-01 Full Text Available ABSTRACT BACKGROUND: Fatigue is a common complaint in cirrhotic patients and may be considered a debilitating symptom with negative impact on quality of life. Research on its etiology and treatment has been hampered by the lack of relevant and reproducible measures of fatigue. OBJECTIVE: To evaluate the psychometric properties of the Fatigue Severity Scale (FSS in cirrhotic patients and to correlate with depressive symptomatology and quality of life. METHODS: Cross-sectional study with a convenience sample of 106 cirrhotic patients, aged between 18 and 70 years, both genders, literate, pre and post liver transplantation in outpatient follow-up. Internal consistency, reproducibility, discriminant validity, criterion validity, construct validity, responsiveness criterion, depressive symptomatology and quality of life were evaluated through questionnaires between January and October 2015. RESULTS: The mean age was 54.75±9.9 years, 65.1% male and 32.1% of the sample had cirrhosis due to hepatitis C virus. The mean FSS score was 4.74±1.64. Cronbach’s alpha was 0.93, and the Intraclass Correlation Coefficient was 0.905 (95% CI: 0.813-0.952. For discriminant validity, FSS differentiated scores from different groups (P=0.009 and presented a correlation with the Modified Fatigue Impact Scale (r=0.606, P=0.002. FSS correlated significantly and positively with depressive symptomatology and correlated negatively with the SF-36 domains for construct validity. For responsiveness, no significant changes were observed in the fatigue scores in the pre and post-liver transplantation periods (P=0.327. CONCLUSION: FSS showed good psychometric performance in the evaluation of fatigue in patients with cirrhosis. Fatigue presented a strong correlation with depressive symptomatology and quality of life. 18. Effect of electric discharge machining on the fatigue life of Inconel 718 Science.gov (United States) Jeelani, S.; Collins, M. R. 1988-01-01 The effect of electric discharge machining on the fatigue life of Inconel 718 alloy at room temperature was investigated. Data were generated in the uniaxial tension fatigue mode at ambient temperature using flat 3.175 mm thick specimens. The specimens were machined on a wire-cut electric discharge machine at cutting speeds ranging from 0.5 to 2 mm per minute. The specimens were fatigued at a selected stress, and the resulting fatigue lives compared with that of the virgin material. The surfaces of the fatigued specimens were examined under optical and scanning electron microscopes, and the roughness of the surfaces was measured using a standard profilometer. From the results of the investigation, it was concluded that the fatigue life of the specimens machined using EDM decreased slightly as compared with that of the virgin material, but remained unchanged as the cutting speed was changed. The results are explained using data produced employing microhardness measurements, profilometry, and optical and scanning microscopy. 19. Influences of size and position of defects on the fatigue life of electron beam welded-aluminum alloy joints Institute of Scientific and Technical Information of China (English) LU Li; ZHAO Haiyan; CAI Zhipeng; CUI Xiaofang 2007-01-01 Defects such as pores influence the fatigue life of electron beam-welded aluminum alloy joints. In this paper,the influences of pore size and position on the fatigue life of aluminum overlap joint are studied. A finite element model (FEM), combined with experimental data, is established to evaluate the fatigue life of overlap joints. By employing this FE model, the effects of pore size and position on fatigue lives of overlap joints are investigated and discussed. From the present study, when pore position is closer to the weld bead tip or the faying surface, the fatigue life decreases. Also, there is a critical size for the pore; when the pore size is larger than the critical value, the fatigue strength decreases sharply. 20. Fatigue Life Prediction of Ductile Iron Based on DE-SVM Algorithm Science.gov (United States) Yiqun, Ma; Xiaoping, Wang; lun, An the model, predicting fatigue life of ductile iron, based on SVM (Support Vector Machine, SVM) has been established. For it is easy to fall into local optimum during parameter optimization of SVM, DE (Differential Evolution algorithm, DE) algorithm was adopted to optimize to improve prediction precision. Fatigue life of ductile iron is predicted combining with concrete examples, and simulation experiment to optimize SVM is conducted adopting GA (Genetic Algorithm), ACO (Ant Colony Optimization) and POS (Partial Swarm Optimization). Results reveal that DE-SVM algorithm is of a better prediction performance. 1. Case Studies of Fatigue Life Improvement Using Low Plasticity Burnishing in Gas Turbine Engine Applications Science.gov (United States) Prevey, Paul S.; Shepard, Michael; Ravindranath, Ravi A.; Gabb, Timothy 2003-01-01 Surface enhancement technologies such as shot peening, laser shock peening (LSP), and low plasticity burnishing (LPB) can provide substantial fatigue life improvement. However, to be effective, the compressive residual stresses that increase fatigue strength must be retained in service. For successful integration into turbine design, the process must be affordable and compatible with the manufacturing environment. LPB provides thermally stable compression of comparable magnitude and even greater depth than other methods, and can be performed in conventional machine shop environments on CNC machine tools. LPB provides a means to extend the fatigue lives of both new and legacy aircraft engines and ground-based turbines. Improving fatigue performance by introducing deep stable layers of compressive residual stress avoids the generally cost prohibitive alternative of modifying either material or design. The X-ray diffraction based background studies of thermal and mechanical stability of surface enhancement techniques are briefly reviewed, demonstrating the importance of minimizing cold work. The LPB process, tooling, and control systems are described. An overview of current research programs conducted for engine OEMs and the military to apply LPB to a variety of engine and aging aircraft components are presented. Fatigue performance and residual stress data developed to date for several case studies are presented including: * The effect of LPB on the fatigue performance of the nickel based super alloy IN718, showing fatigue benefit of thermal stability at engine temperatures. * An order of magnitude improvement in damage tolerance of LPB processed Ti-6-4 fan blade leading edges. * Elimination of the fretting fatigue debit for Ti-6-4 with prior LPB. * Corrosion fatigue mitigation with LPB in Carpenter 450 steel. *Damage tolerance improvement in 17-4PH steel. Where appropriate, the performance of LPB is compared to conventional shot peening after exposure to engine 2. A computational approach for thermomechanical fatigue life prediction of dissimilarly welded superheater tubes Energy Technology Data Exchange (ETDEWEB) Krishnasamy, Ram-Kumar; Seifert, Thomas; Siegele, Dieter [Fraunhofer-Institut fuer Werkstoffmechanik (IWM), Freiburg im Breisgau (Germany) 2010-07-01 In this paper a computational approach for fatigue life prediction of dissimilarly welded superheater tubes is presented and applied to a dissimilar weld between tubes made of the nickel base alloy Alloy617 tube and the 12% chromium steel VM12. The approach comprises the calculation of the residual stresses in the welded tubes with a multi-pass dissimilar welding simulation, the relaxation of the residual stresses in a post weld heat treatment (PWHT) simulation and the fatigue life prediction using the remaining residual stresses as initial condition. A cyclic fiscoplasticity model is used to calculate the transient stresses and strains under thermocyclic service loadings. The fatigue life is predicted with a damage parameter which is based on fracture mechanics. The adjustable parameters of the model are determined based on LCF and TMF experiments. The simulations show, that the residual stresses that remain after PWHT further relax in the first loading cycles. The predicted fatigue lives depend on the residual stresses and, thus, on the choice of the loading cycle in which the damage parameter is evaluated. It the first loading cycle, where residual stresses are still present, is considered, lower fatigue lives are predicted compared to predictions considering loading cycles with relaxed residual stresses. (orig.) 3. Deep surface rolling for fatigue life enhancement of laser clad aircraft aluminium alloy Energy Technology Data Exchange (ETDEWEB) Zhuang, W., E-mail: wyman.zhuang@dsto.defence.gov.au [Aerospace Division, Defence Science and Technology Organisation, 506 Lorimer Street, Fishermans Bend, Victoria 3207 (Australia); Liu, Q.; Djugum, R.; Sharp, P.K. [Aerospace Division, Defence Science and Technology Organisation, 506 Lorimer Street, Fishermans Bend, Victoria 3207 (Australia); Paradowska, A. [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2232 (Australia) 2014-11-30 Highlights: • Deep surface rolling as a post-repair enhancement technology was applied to the laser cladded 7075-T651 aluminium alloy specimens that simulated corrosion damage blend-out repair. • The residual stresses induced by the deep surface rolling process were measured. • The deep surface rolling process can introduce deep and high magnitude compressive residual stresses beyond the laser clad and substrate interface. • Spectrum fatigue test showed the fatigue life was significantly increased by deep surface rolling. - Abstract: Deep surface rolling can introduce deep compressive residual stresses into the surface of aircraft metallic structure to extend its fatigue life. To develop cost-effective aircraft structural repair technologies such as laser cladding, deep surface rolling was considered as an advanced post-repair surface enhancement technology. In this study, aluminium alloy 7075-T651 specimens with a blend-out region were first repaired using laser cladding technology. The surface of the laser cladding region was then treated by deep surface rolling. Fatigue testing was subsequently conducted for the laser clad, deep surface rolled and post-heat treated laser clad specimens. It was found that deep surface rolling can significantly improve the fatigue life in comparison with the laser clad baseline repair. In addition, three dimensional residual stresses were measured using neutron diffraction techniques. The results demonstrate that beneficial compressive residual stresses induced by deep surface rolling can reach considerable depths (more than 1.0 mm) below the laser clad surface. 4. Fatigue Life Prediction of Multi Leaf Spring used in the Suspension System of Light Commercial Vehicle Directory of Open Access Journals (Sweden) V.K.Aher 2012-06-01 Full Text Available The Leaf spring is widely used in automobiles and one of the components of suspension system. It needs to have high fatigue life. As a general rule, the leaf spring is regarded as a safety component as failure could lead to severe accidents. The purpose of this paper is to predict the fatigue life of steel leaf spring along with analytical stress and deflection calculations. This present work describes static and fatigue analysis of a steel leaf spring of a light commercial vehicle (LCV. The dimensions of the leaf spring of a LCV are taken and are verified by design calculations. The non-linear static analysis of 2D model of the leaf spring is performed using NASTRAN solver and compared with analytical results. The preprocessing of the model is done by using HYPERMESH software. The stiffness of the leaf spring is studied by plotting load versus deflection curve for various load applications. The simulation results are compared with analytical results. The fatigue life of the leaf spring is predicted using MSC Fatigue software. 5. Effect of pre-deformation on the fatigue crack initiation life of X60 pipeline steel Energy Technology Data Exchange (ETDEWEB) Zheng, M. [School of Materials Science and Engineering, Xi' an Jiaotong University, Xi' an 710049 (China)]. E-mail: mszheng@mail.xjtu.edu.cn; Luo, J.H. [School of Materials Science and Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Tubular Goods Research Center, CNPC, Xi' an 710065 (China); Zhao, X.W. [School of Materials Science and Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Tubular Goods Research Center, CNPC, Xi' an 710065 (China); Bai, Z.Q. [School of Materials Science and Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Tubular Goods Research Center, CNPC, Xi' an 710065 (China); Wang, R. [School of Mechanical Engineering, Xi' an Petroleum University, Xi' an 710065 (China) 2005-07-01 It is impossible to keep petroleum and natural gas transmission pipelines free from defects in the manufacturing, installation and servicing processes. The damage might endanger the safety of pipelines and even shorten their service life; gas or petroleum release due to defects may jeopardise the surrounding ecological environments with associated economic and life costs. Pre-tensile deformation of X60 steel is employed to experimentally simulate the influence of dents on the fatigue crack initiation life. The investigation indicates that the fatigue crack initiation life of pre-deformed X60 pipeline steel can be assessed by a previously proposed energetic approach. The threshold for crack initiation increases with the pre-deformation due to a strain hardening effect, while the fatigue resistant factor exhibits a maximum with pre-deformation owing to its special dependence on fracture strain and fracture strength. The result is expected to be beneficial to the understanding of the effect of damage on the safety of pipelines and fatigue life prediction. 6. A study on the fatigue life prediction of the various gas-welded joints using a probabilistic statistics technique Science.gov (United States) Baek, Seung Yeb; Bae, Dong Ho 2011-02-01 Gas welding is a very important and useful technology in the fabrication of railroad cars and commercial vehicle structures. However, since the fatigue strength of gas-welded joints is considerably lower than that of the base of material due to stress concentration at the weld, the fatigue strength assessment of gas-welded joints is very important for the reliability and durability of railroad cars and establishment of criteria for long-life fatigue design. In this study, after evaluating the fatigue strength using a simulated specimen that satisfies not only the structural characteristics but also the mechanical condition of the actual structure, the fatigue design criteria are determined and applied to the fatigue design of the gas welded body structure. To save time and cost for the fatigue design, we investigated an accelerated life-prediction using a probabilistic statistics technique based on the theory of statistical reliability. The (Δσ a )R-Nf relationship was obtained from actual fatigue test data, including welding residual stress. On the basis of these results, the (Δσa)R-(Nf)ALP relationship that was derived from statistical probability analysis was compared with the actual fatigue test data. Therefore, it is expected that the accelerated life prediction will provide a useful method of determining the criteria for fatigue design and predicting a specific target life. 7. Evaluation of fatigue life via stress and strain damage criterions Science.gov (United States) Savkin, A. N.; Sedov, A. A.; Badikov, K. A. 2016-11-01 Attempts to describe the effect of the variable amplitude loading character on fatigue damage accumulation are made for a structural steel element. We show the possibility of durability prediction of steel taking into account stress and strain parameters of stationary cyclic loading and parameters that describe the range of random loading. It is proposed to quantify the influence of the loading character on durability by a damage model with the nonstationarity factor and spectrum fullness factor. The accuracy of the model is analyzed on the basis of steel 40Cr tests. The experimental evidence and analytical results of the proposed model are correlated. 8. Statistical analysis of manufacturing defects on fatigue life of wind turbine casted Component DEFF Research Database (Denmark) Rafsanjani, Hesam Mirzaei; Sørensen, John Dalsgaard; Mukherjee, Krishnendu; 2014-01-01 and size of defects in the casted components and is therefore rather uncertain and needs to be described by stochastic models. Uncertainties related to such defects influence prediction of the fatigue strengths and are therefore important in modelling and assessment of the reliability of wind turbine...... for the fatigue life, namely LogNormal and Weibull distributions. The statistical analyses are performed using the Maximum Likelihood Method and the statistical uncertainty is estimated. Further, stochastic models for the fatigue life obtained from the statistical analyses are used for illustration to assess...... components. The defect distribution is usually affected by the manufacturing process. In this paper, two methods of casting, sand casting and chill casting are considered. These are compared in statistical analyses of a large number of representative test samples using two basic stochastic models... 9. Anisotropic Elastoplastic Damage Mechanics Method to Predict Fatigue Life of the Structure Directory of Open Access Journals (Sweden) Hualiang Wan 2016-01-01 Full Text Available New damage mechanics method is proposed to predict the low-cycle fatigue life of metallic structures under multiaxial loading. The microstructure mechanical model is proposed to simulate anisotropic elastoplastic damage evolution. As the micromodel depends on few material parameters, the present method is very concise and suitable for engineering application. The material parameters in damage evolution equation are determined by fatigue experimental data of standard specimens. By employing further development on the ANSYS platform, the anisotropic elastoplastic damage mechanics-finite element method is developed. The fatigue crack propagation life of satellite structure is predicted using the present method and the computational results comply with the experimental data very well. 10. EVALUATION OF THE PROBABILITY DISTRIBUTION OF PITTING CORROSION FATIGUE LIFE IN AIRCRAFT MATERIALS Institute of Scientific and Technical Information of China (English) 王清远; N.KAWAGOISHI; Q.CHEN; R.M.PIDAPARTI 2003-01-01 Corrosion and fatigue properties of aircraft materials axe known to have a considerablescatter due to the random nature of materials, loading, and environmental conditions. A probabilisticapproach for predicting the pitting corrosion fatigue life has been investigated which captures the effectof the interaction of the cyclic load and corrosive environment and all stages of the corrosion fatigueprocess (i.e. the pit nucleation and growth, pit-crack transition, short- and long-crack propagation).The probabilistic model investigated considers the uncertainties in the initial pit size, corrosion pittingcurrent, and material properties due to the scatter found in the experimental data. Monte Carlo simu-lations were performed to define the failure probability distribution. Predicted cumulative distributionfunctions of fatigue life agreed reasonably well with the existing experimental data. 11. Influence of fibre volume fraction and temperature on fatigue life of glass fibre reinforced plastics Directory of Open Access Journals (Sweden) Konrad Wegener 2016-07-01 Full Text Available The influence of fibre volume fraction and temperature on fatigue life of continuous glass fibre reinforced plastics is investigated in detail. The physical causes of the two effects on the slope of the S-N-curve in fibre direction at R = 0.1 are researched and can be explained with help of micrographs. A new phenomenological approach is presented to model both effects in fibre dominated laminates with different stacking sequences using only the static ultimate strength as an input. Static and fatigue tests of different layups and fibre volume fractions are performed at different temperatures to validate the fatigue life predictions. Additionally it is derived that there is an optimal fibre volume fraction regarding a minimum damage sum. This fibre volume fraction is dependent on a given loading spectra and can be calculated using the phenomenological model. 12. Noncontact monitoring of surface-wave nonlinearity for predicting the remaining life of fatigued steels Science.gov (United States) Ogi, Hirotsugu; Hirao, Masahiko; Aoki, Shinji 2001-07-01 A nonlinear acoustic measurement is studied for fatigue damage monitoring. An electromagnetic acoustic transducer (EMAT) magnetostrictively couples to a surface-shear-wave resonance along the circumference of a rod specimen during rotating bending fatigue of carbon steels. Excitation of the EMAT at half of the resonance frequency caused the standing wave to contain only the second-harmonic component, which was received by the same EMAT to determine the second-harmonic amplitude. Thus measured surface-wave nonlinearity always showed two distinct peaks at 60% and 85% of the total life. We attribute the earlier peak to crack nucleation and growth, and the later peak to an increase of free dislocations associated with crack extension in the final stage. This noncontact resonance-EMAT measurement can monitor the evolution of the surface-shear-wave nonlinearity throughout the metal's fatigue life and detect the pertinent precursors of the eventual failure. 13. Fatigue life prediction of Ni-base thermal solar receiver tubes Energy Technology Data Exchange (ETDEWEB) Hartrott, Philipp von; Schlesinger, Michael [Fraunhofer-Institut fuer Werkstoffmechanik (IWM), Freiburg im Breisgau (Germany); Uhlig, Ralf; Jedamski, Jens [DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Stuttgart (Germany) 2010-07-01 Solar receivers for tower type Solar Thermal Power Plants are subjected to complex thermo-mechanical loads including fast and severe thermo-mechanical cycles. The material temperatures can reach more than 800 C and fall to room temperature very quickly. In order to predict the fatigue life of a receiver design, receiver tubes made of Alloy 625 with a wall thickness of 0.5 mm were tested in isothermal and thermo-cyclic experiments. The number of cycles to failure was in the range of 100 to 100,000. A thermo-mechanical fatigue life prediction model was set up. The model is based on the cyclic deformation of the material and the damage caused by the growth of fatigue micro cracks. The model reasonably predicts the experimental results. (orig.) 14. Bi-variable damage model for fatigue life prediction of metal components Institute of Scientific and Technical Information of China (English) Miao Zhang; Qing-Chun Meng; Xing Zhang; Wei-Ping Hu 2011-01-01 Based on the theory of continuum damage mechanics, a bi-variable damage mechanics model is developed, which, according to thermodynamics, is accessible to derivation of damage driving force, damage evolution equation and damage evolution criteria. Furthermore, damage evolution equations of time rate are established by the generalized Drucker's postulate. The damage evolution equation of cycle rate is obtained by integrating the time damage evolution equations, and the fatigue life prediction method for smooth specimens under repeated loading with constant strain amplitude is constructed. Likewise, for notched specimens under the repeated loading with constant strain amplitude, the fatigue life prediction method is obtained on the ground of the theory of conservative integral in damage mechanics. Thus, the material parameters in the damage evolution equation can be obtained by reference to the fatigue test results of standard specimens with stress concentration factor equal to 1, 2 and 3. 15. A new Cumulative Damage Model for Fatigue Life Prediction under Shot Peening Treatment Directory of Open Access Journals (Sweden) Abdul-Jabar H. Ali 2015-07-01 Full Text Available In this paper, fatigue damage accumulation were studied using many methods i.e.Corton-Dalon (CD,Corton-Dalon-Marsh(CDM, new non-linear model and experimental method. The prediction of fatigue lifetimes based on the two classical methods, Corton-Dalon (CDandCorton-Dalon-Marsh (CDM, are uneconomic and non-conservative respectively. However satisfactory predictions were obtained by applying the proposed non-linear model (present model for medium carbon steel compared with experimental work. Many shortcomings of the two classical methods are related to their inability to take into account the surface treatment effect as shot peening. It is clear that the new model shows that a much better and conservative prediction of fatigue life in comparison with CD and CDM methods. The prediction of the present model gave slightly below the experimental data while the CDM gave overestimate prediction and CD showed strongly underestimates the life of specimens. 16. Thermomechanical fatigue – Damage mechanisms and mechanism-based life prediction methods Indian Academy of Sciences (India) H-J Christ; A Jung; H J Maier; R Teteruk 2003-02-01 An existing extensive database on the isothermal and thermomechanical fatigue behaviour of high-temperature titanium alloy IMI 834 and dispersoidstrengthened aluminum alloy X8019 in SiC particle-reinforced as well as unreinforced conditions was used to evaluate both the adaptability of fracture mechanics approaches to TMF and the resulting predictive capabilities of determining material life by crack propagation consideration. Selection of the correct microstructural concepts was emphasised and these concepts were, then adjusted by using data from independent experiments in order to avoid any sort of ﬁtting. It is shown that the cyclic -integral ($\\Delta J_{\\text{eff}}$concept) is suitable to predict the cyclic lifetime for conditions where the total crack propagation rate is approximately identical to pure fatigue crack growth velocity. In the case that crack propagation is strongly affected by creep, the creep–fatigue damage parameter$\\Delta_{C\\ F}\$ introduced by Riedel can be successfully applied. If environmental effects are very pronounced, the accelerating inﬂuence of corrosion on fatigue crack propagation can no longer implicitly be taken into account in the fatigue crack growth law. Instead, a linear combination of the crack growth rate contributions from plain fatigue (determined in vacuum) and from environmental attack is assumed and found to yield a satisfactory prediction, if the relevant corrosion process is taken into account.

17. Initiation and propagation life distributions of fatigue cracks and the life evaluation in high cycle fatigue of ADI; ADI zai no ko cycle hiro kiretsu hassei shinten jumyo bunpu tokusei to jumyo hyoka

Energy Technology Data Exchange (ETDEWEB)

Ochi, Y.; Ishii, A. [University of Electro Communications, Tokyo (Japan); Ogata, T. [Hitachi Metals, Ltd., Tokyo (Japan); Kubota, M. [Kyushu University, Fukuoka (Japan). Faculty of Engineering

1997-10-15

Rotating bending fatigue tests were carried out on austempered ductile cast iron (ADI) in order to investigate the statistical properties of life distributions of crack initiation and propagation, and also the evaluation of fatigue life. The results are summarized as follows: (1) The size of crack initiation sites of the material was represented by a Weibull distribution without regarding to the kinds of crack initiation sites such as microshrinkage and graphite grain. The crack initiation life scattered widely, but the scatter became much smaller as soon as the cracks grew. (2) The crack propagation life Nac which was defined as the minimum crack propagation rate showed lower scatter than the crack initation life. (3) The fatigue life of the material was evaluated well by Nac and the propagation rate after Nac. It was clear that the fatigue life of ductile cast iron was goverened by the scatter of Nac. 8 refs., 13 figs., 4 tabs.

18. Effect of creep and oxidation on reduced fatigue life of Ni-based alloy 617 at 850 °C

Energy Technology Data Exchange (ETDEWEB)

Chen, Xiang, E-mail: chenx@ornl.gov [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, 104 South Wright Street, Urbana, IL 61801 (United States); Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831 (United States); Yang, Zhiqing [Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831 (United States); Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Sokolov, Mikhail A.; Erdman, Donald L. [Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831 (United States); Mo, Kun; Stubbins, James F. [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, 104 South Wright Street, Urbana, IL 61801 (United States)

2014-01-15

Low cycle fatigue (LCF) and creep–fatigue testing of Ni-based alloy 617 was carried out at 850 °C. Compared with its LCF life, the material’s creep–fatigue life decreases to different extents depending on test conditions. To elucidate the microstructure-fatigue property relationship for alloy 617 and the effect of creep and oxidation on its fatigue life, systematic microstructural investigations were carried out using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron backscatter diffraction (EBSD). In LCF tests, as the total strain range increased, deformations concentrated near high angle grain boundaries (HAGBs). The strain hold period in the creep–fatigue tests introduced additional creep damage to the material, which revealed the detrimental effect of the strain hold time on the material fatigue life in two ways. First, the strain hold time enhanced the localized deformation near HAGBs, resulting in the promotion of intergranular cracking of alloy 617. Second, the strain hold time encouraged grain boundary sliding, which resulted in interior intergranular cracking of the material. Oxidation accelerated the initiation of intergranular cracking in alloy 617. In the crack propagation stage, if oxidation was promoted and the cyclic oxidation damage was greater than the fatigue damage, oxidation-assisted intergranular crack growth resulted in a significant reduction in the material’s fatigue life.

19. Effect of Creep and Oxidation on Reduced Creep-Fatigue life of Ni-based Alloy 617 at 850 C

Energy Technology Data Exchange (ETDEWEB)

Chen, Xiang [ORNL; Yang, Zhiqing [ORNL; Sokolov, Mikhail A [ORNL; ERDMAN III, DONALD L [ORNL; Mo, Kun [ORNL; Stubbins, James [ORNL

2014-01-01

Low cycle fatigue (LCF) and creep fatigue testing of Ni-based alloy 617 was carried out at 850 C. Compared with its LCF life, the material s creep fatigue life decreases to different extents depending on test conditions. To elucidate the microstructure-fatigue property relationship for alloy 617 and the effect of creep and oxidation on its fatigue life, systematic microstructural investigations were carried out using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron backscatter diffraction (EBSD). In LCF tests, as the total strain range increased, deformations concentrated near high angle grain boundaries (HAGBs). The strain hold period in the creep fatigue tests introduced additional creep damage to the material, which revealed the detrimental effect of the strain hold time on the material fatigue life in two ways. First, the strain hold time enhanced the localized deformation near HAGBs, resulting in the promotion of intergranular cracking of alloy 617. Second, the strain hold time encouraged grain boundary sliding, which resulted in interior intergranular cracking of the material. Oxidation accelerated the initiation of intergranular cracking in alloy 617. In the crack propagation stage, if oxidation was promoted and the cyclic oxidation damage was greater than the fatigue damage, oxidation-assisted intergranular crack growth resulted in a significant reduction in the material s fatigue life.

20. SHM-Based Probabilistic Fatigue Life Prediction for Bridges Based on FE Model Updating.

Science.gov (United States)

Lee, Young-Joo; Cho, Soojin

2016-03-02

Fatigue life prediction for a bridge should be based on the current condition of the bridge, and various sources of uncertainty, such as material properties, anticipated vehicle loads and environmental conditions, make the prediction very challenging. This paper presents a new approach for probabilistic fatigue life prediction for bridges using finite element (FE) model updating based on structural health monitoring (SHM) data. Recently, various types of SHM systems have been used to monitor and evaluate the long-term structural performance of bridges. For example, SHM data can be used to estimate the degradation of an in-service bridge, which makes it possible to update the initial FE model. The proposed method consists of three steps: (1) identifying the modal properties of a bridge, such as mode shapes and natural frequencies, based on the ambient vibration under passing vehicles; (2) updating the structural parameters of an initial FE model using the identified modal properties; and (3) predicting the probabilistic fatigue life using the updated FE model. The proposed method is demonstrated by application to a numerical model of a bridge, and the impact of FE model updating on the bridge fatigue life is discussed.

1. Compassion Fatigue, Compassion Satisfaction, and Burnout: Factors Impacting a Professional's Quality of Life

Science.gov (United States)

Sprang, Ginny; Whitt-Woosley, Adrienne; Clark, James J.

2007-01-01

This study examined the relationship between three variables, compassion fatigue (CF), compassion satisfaction (CS), and burnout, and provider and setting characteristics in a sample of 1,121 mental health providers in a rural southern state. Respondents completed the Professional Quality of Life Scale as part of a larger survey of provider…

2. Effect of Defects Distribution on Fatigue Life of Wind Turbine Components

DEFF Research Database (Denmark)

Rafsanjani, Hesam Mirzaei; Sørensen, John Dalsgaard

2015-01-01

by a Poisson process / field where the defects form clusters that consist of a parent defect and related defects around the parent defect. The fatigue life is dependent on the number, type, location and size of the defects in the component and is therefore quite uncertain and needs to be described...

3. Quality of Life in Patients with Multiple Sclerosis: The Impact of Depression, Fatigue, and Disability

Science.gov (United States)

Goksel Karatepe, Altlnay; Kaya, Taciser; Gunaydn, Rezzan; Demirhan, Aylin; Ce, Plnar; Gedizlioglu, Muhtesem

2011-01-01

Aim: The aim of this study was to assess the quality of life (QoL) in patients with multiple sclerosis (MS), and to evaluate its association with disability and psychosocial factors especially depression and fatigue. Methods: Demographic characteristics, education level, disease severity, and disease duration were documented for each patient. QoL,…

4. Crack mode and life of Ti-6Al-4V under multiaxial low cycle fatigue

Directory of Open Access Journals (Sweden)

Takamoto Itoh

2015-10-01

Full Text Available This paper studies multiaxial low cycle fatigue crack mode and failure life of Ti-6Al-4V. Stress controlled fatigue tests were carried out using a hollow cylinder specimen under multiaxial loadings of λ=0, 0.4, 0.5 and 1 of which stress ratio R=0 at room temperature. λ is a principal stress ratio and is defined as λ=II/I, where I and II are principal stresses of which absolute values take the largest and middle ones, respectively. Here, the test at λ=0 is a uniaxial loading test and that at λ=1 an equi-biaxial loading test. A testing machine employed is a newly developed multiaxial fatigue testing machine which can apply push-pull and reversed torsion loadings with inner pressure onto the hollow cylinder specimen. Based on the obtained results, this study discusses evaluation of the biaxial low cycle fatigue life and crack mode. Failure life is reduced with increasing λ induced by cyclic ratcheting. The crack mode is affected by the surface condition of cut-machining and the failure life depends on the crack mode in the multiaxial loading largely.

5. Structural fatigue life assessment and sustainment implications for a New Class of US Coast Guard Cutters

NARCIS (Netherlands)

Stambaugh, K.; Drummen, I.; Cleary, C.; Sheinberg, R.; Kaminski, M.L.

2014-01-01

This paper presents an overview of the US Coast Guard’s Fatigue Life Assessment Project (FLAP) and the application of the results in hull structure lifecycle management of the National Security Cutter class. One of the key measurements of the FLAP instrumentation included a radar based wave data

6. Evaluation of health-related quality of life, fatigue and depression in neuromyelitis optica.

Science.gov (United States)

Chanson, J-B; Zéphir, H; Collongues, N; Outteryck, O; Blanc, F; Fleury, M; Vermersch, P; de Seze, J

2011-06-01

The burden of multiple sclerosis (MS) includes fatigue, depression and worsening of health-related quality of life (HRQOL). These changes have not been yet measured in neuromyelitis optica (NMO). Our aim was to assess the HRQOL, fatigue and depression in NMO. We administered French validated self-questionnaires on HRQOL (SEP-59), fatigue (EMIF-SEP) and depression (EHD) to 40 patients followed up in two centres. We assessed the relationship of these parameters with gender, age, disability, disease duration, visual acuity and NMO-antibody status and also compared our results with equivalent data in MS and normal subjects derived from previous studies. Health-related quality of life scores were lower (P < 0.01) in patients with NMO when compared to normal subjects. No significant difference was noted between patients with NMO and MS for most scores, the exceptions being HRQOL related to cognitive function (better in NMO than in MS), HRQOL related to sphincter dysfunction (worse in NMO than in MS) and the psychological dimension of fatigue (milder in NMO than in MS). Disability was the main predictive factor of an unfavourable evolution. This study reveals the strong impact of NMO on HRQOL, fatigue and depression and the importance of screening patients, especially the more disabled, so as to initiate suitable treatment. © 2010 The Author(s). European Journal of Neurology © 2010 EFNS.

7. Cyclic fatigue damage characteristics observed for simple loadings extended to multiaxial life prediction

Science.gov (United States)

Jones, David J.; Kurath, Peter

1988-01-01

Fully reversed uniaxial strain controlled fatigue tests were performed on smooth cylindrical specimens made of 304 stainless steel. Fatigue life data and cracking observations for uniaxial tests were compared with life data and cracking behavior observed in fully reversed torsional tests. It was determined that the product of maximum principle strain amplitude and maximum principle stress provided the best correlation of fatigue lives for these two loading conditions. Implementation of this parameter is in agreement with observed physical damage and it accounts for the variation of stress-strain response, which is unique to specific loading conditions. Biaxial fatigue tests were conducted on tubular specimens employing both in-phase and out-of-phase tension torsion cyclic strain paths. Cracking observations indicated that the physical damage which occurred in the biaxial tests was similar to the damage observed in uniaxial and torsional tests. The Smith, Watson, and Topper parameter was then extended to predict the fatigue lives resulting from the more complex loading conditions.

8. Novel Electrochemical Test Bench for Evaluating the Functional Fatigue Life of Biomedical Alloys

Science.gov (United States)

Ijaz, M. F.; Dubinskiy, S.; Zhukova, Y.; Korobkova, A.; Pustov, Y.; Brailovski, V.; Prokoshkin, S.

2017-08-01

The aim of the present work was first to develop and validate a test bench that simulates the in vitro conditions to which the biomedical implants will be actually subjected in vivo. For the preliminary application assessments, the strain-controlled fatigue tests of biomedically pure Ti and Ti-Nb-Zr alloy in simulated body fluid were undertaken. The in situ open-circuit potential measurements from the test bench demonstrated a strong dependence on the dynamic cycling and kind of material under testing. The results showed that during fatigue cycling, the passive oxide film formed on the surface of Ti-Nb-Zr alloy was more resistant to fatigue degradation when compared with pure Ti. The Ti-Nb-Zr alloy exhibited prolonged fatigue life when compared with pure Ti. The fractographic features of both materials were also characterized using scanning electron microscopy. The electrochemical results and the fractographic evidence confirmed that the prolonged functional fatigue life of the Ti-Nb-Zr alloy is apparently ascribable to the reversible martensitic phase transformation.

9. A Multiaxial Low Cycle Fatigue Life Prediction Model for Both Proportional and Non-proportional Loading Conditions

Science.gov (United States)

Paul, Surajit Kumar

2014-09-01

This paper has presented a life prediction model in the field of multiaxial low-cycle fatigue. The proposed model is generally applied for constant amplitude multiaxial proportional and non-proportional loading. Depending upon applied strain path the equivalent strain varies within a cycle. Equivalent average strain amplitude is considered as fatigue damage parameter in the proposed model. The model has requirement of only two material constants and no other tuning parameters. The model is examined by the proportional and non-proportional low-cycle fatigue life experimental data for eight different types of materials. The model is successfully correlated with multiaxial fatigue lives of eight different materials.

10. Fatigue Life Improving of Drill Rod by Inclusion Control

Science.gov (United States)

Wang, Linzhu; Yang, Shufeng; Li, Jingshe; Liu, Wei; Zhou, Yinghao

2016-08-01

Large and hard inclusions often deteriorate the service performance and reduce the fatigue lifetime of drill rods. In this paper, the main reasons of the rupture of drill rods were analyzed by the examination of their fracture and it is found that the large inclusions were the main reason of breakage of rod drill. The inclusions were high of Ca content or Al2O3 rich. Smaller and better deformability inclusions were obtained by the optimization of refining slag, calcium treatment process and the flow control devices of tundish. Results of industrial experiment after optimization show that total oxygen content of drill rods decreased by more than 50%, macro-inclusions weight fraction decreased from about 4 mg/10 kg to about 0.3 mg/10 kg and the micro-inclusions average size decreased from 6 to 3.6 μm. The average using times of drill rods after optimization were increased by about 60%.

11. Prediction of Fatigue Life of Boom Nose End Casting Using Linear Elastic Fracture Mechanics

OpenAIRE

2014-01-01

The main objective of this study is to get the life estimation of Boom nose end casting using theoretical approach and compaired it with finite element method. Therefore, this study consists of three major sections : (1) dynamic load analysis (2) FEM and stress analysis (3) prediction of fatigue life for Boom nose end casting. In this study a dynamic loads were obtained from cyclic loading at different time. Finite element analysis was performed to obtain the variation of stress...

12. Fatigue Life of Cast Titanium Alloys Under Simulated Denture Framework Displacements

Science.gov (United States)

Koike, Mari; Chan, Kwai S.; Hummel, Susan K.; Mason, Robert L.; Okabe, Toru

2013-02-01

The objective of the study was to evaluate the hypothesis that the mechanical properties and fatigue behavior of removable partial dentures (RPD) made from cast titanium alloys can be improved by alloying with low-cost, low-melting elements such as Cu, Al, and Fe using commercially pure Ti (CP-Ti) and Ti-6Al-4V as controls. RPD specimens in the form of rest-shaped, clasp, rectangular-shaped specimens and round-bar tensile specimens were cast using an experimental Ti-5Al-5Cu alloy, Ti-5Al-1Fe, and Ti-1Fe in an Al2O3-based investment with a centrifugal-casting machine. The mechanical properties of the alloys were determined by performing tensile tests under a controlled displacement rate. The fatigue life of the RPD specimens was tested by the three-point bending in an MTS testing machine under a cyclic displacement of 0.5 mm. Fatigue tests were performed at 10 Hz at ambient temperature until the specimens failed into two pieces. The tensile data were statistically analyzed using one-way ANOVA (α = 0.05) and the fatigue life data were analyzed using the Kaplan-Meier survival analysis (α = 0.05). The experimental Ti-5Al-5Cu alloy showed a significantly higher average fatigue life than that of either CP-Ti or Ti-5Al-1Fe alloy ( p casting pores. Among the alloys tested, the Ti-5Al-5Cu alloy exhibited favorable results in fabricating dental appliances with an excellent fatigue behavior compared with other commercial alloys.

13. Fatigue Life Prediction of 2D Woven Ceramic-Matrix Composites at Room and Elevated Temperatures

Science.gov (United States)

Longbiao, Li

2017-02-01

In this paper, the fatigue life of 2D woven ceramic-matrix composites, i.e., SiC/SiC, SiC/Si-N-C, SiC/Si-B4C, and Nextel 610™/Aluminosilicate, at room and elevated temperatures has been predicted using the micromechanics approach. An effective coefficient of the fiber volume fraction along the loading direction (ECFL) was introduced to describe the fiber architecture of preforms. The Budiansky-Hutchinson-Evans shear-lag model was used to describe the microstress field of the damaged composite considering fibers failure. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. The interface shear stress and fibers strength degradation model and oxidation region propagation model have been adopted to analyze the fatigue and oxidation effects on fatigue life of the composite, which is controlled by interface frictional slip and diffusion of oxygen gas through matrix multicrackings. Under cyclic fatigue loading, the fibers broken fraction was determined by combining the interface/fiber oxidation model, interface wear model and fibers statistical failure model at elevated temperatures, based on the assumption that the fiber strength is subjected to two-parameter Weibull distribution and the load carried by broken and intact fibers satisfy the Global Load Sharing (GLS) criterion. When the broken fibers fraction approaches to the critical value, the composites fatigue fractures. The fatigue life S-N curves of 2D SiC/SiC, SiC/Si-N-C, SiC/Si-B4C, and Nextel 610™/Aluminosilicate composites at room temperature and 800, 1000 and 1200 °C in air and steam have been predicted.

14. Mechanisms of fatigue-crack initiation and their impact on fatigue life of AlSi7 die-cast components

Directory of Open Access Journals (Sweden)

Redik Sabine

2014-06-01

Full Text Available In the course of the present study, in-situ observations of crack initiation and crack growth of naturally induced cracks in cyclically loaded specimens along with conventional fatigue tests and fracture surface analyses were performed. The specimens used were taken from different sampling positions of standard and HIPed aluminum-die-cast engine blocks, with different cooling conditions. In one sampling position within the standard engine block microporosity was able to form, acting as a source for fatigue-crack initiation. While in the absence of microporosity, as observed in specimens taken from HIPed components, crack initiation occured via slip band mechanism. If material defects such as pores were present, premature crack initiation reduced the fatigue life yielding a lower fatigue life and fatigue strength than specimens where cracks formed by slip band mechanism. For cracks formed at pores, the pore size is the determining factor for fatigue behavior. While for cracks initiated via slip band mechanism fatigue strength is a function of the local material strength.

15. Application of Mathematica Software for Estimate the Fatigue Life Time Duration of Mechanical System

Directory of Open Access Journals (Sweden)

Petru Florin Minda

2010-10-01

Full Text Available The paper present how we can use Mathematica to solve the equations types usually used to determinate the maximum stress cycles that can be support by a mechanical system until he will be out of use. To illustrate the type of equations used in specialized literature to estimate fatigue life time duration was chosen a specific case of mechanical structure applied to fatigue. It is about lever button of runner blade mechanism of Kaplan turbine, that in function support a very intensive alternative strain.

16. Influence of Subgrade and Unbound Granular Layers Stiffness on Fatigue Life of Hot Mix Asphalts - HMA

Directory of Open Access Journals (Sweden)

Hugo A. Rondón-Quintana

2013-11-01

Full Text Available The mainly factors studied to predict fatigue life of hot mix asphalt-HMA in flexible pavements are the loading effect, type of test, compaction methods, design parameters of HMA (e.g., particle size and size distribution curve, fine content, type of bitumen and the variables associated with the environment (mainly moisture, temperature, aging. This study evaluated through a computer simulation, the influence of the granular layers and subgrade on the fatigue life of asphalt layers in flexible pavement structures. Mechanics parameters of granular layers of subgrade, base and subbase were obtained using the mathematical equations currently used for this purpose in the world. The emphasis of the study was the city of Bogotá, where the average annual temperature is 14°C and soils predominantly clay, generally experience CBR magnitudes between 1% and 4%. General conclusion: stiffness of the granular layers and subgrade significantly affect the fatigue resistance of HMA mixtures. Likewise, the use of different equations reported in reference literature in order to characterize granular layers may vary the fatigue life between 4.6 and 48.5 times, varying the thickness of the pavement layers in the design.

17. Bayesian techniques for fatigue life prediction and for inference in linear time dependent PDEs

KAUST Repository

Scavino, Marco

2016-01-08

In this talk we introduce first the main characteristics of a systematic statistical approach to model calibration, model selection and model ranking when stress-life data are drawn from a collection of records of fatigue experiments. Focusing on Bayesian prediction assessment, we consider fatigue-limit models and random fatigue-limit models under different a priori assumptions. In the second part of the talk, we present a hierarchical Bayesian technique for the inference of the coefficients of time dependent linear PDEs, under the assumption that noisy measurements are available in both the interior of a domain of interest and from boundary conditions. We present a computational technique based on the marginalization of the contribution of the boundary parameters and apply it to inverse heat conduction problems.

18. Method to calculate fatigue fracture life of control fissure in perilous rock

Institute of Scientific and Technical Information of China (English)

CHEN Hong-kai; TANG Hong-mei

2007-01-01

Rupture and safety of perilous rock are dominated by control fissure behind perilous rock block. Based on model-Ⅰ and model-Ⅱ stress strength factors of control fissure under acting of weight of perilous rock, water pressure in control fissure and earthquake forces, method to calculate critical linking length of control fissure is established. Take water pressure in control fissure as a variable periodic load, and abide by P-M criterion, when control fissure is filled with water, establish the method to calculate fatigue fracture life of control fissure in critical status by contributing value of stress strength factor stemming from water pressure of control fissure in Paris's fatigue equation. Further, parameters(C and m)of sandstone with quartz and feldspar in the area of the Three Gorges Reservoir of China are obtained by fatigue fracture testing.

19. Effect of test frequency on the in vitro fatigue life of acrylic bone cement.

Science.gov (United States)

Lewis, Gladius; Janna, Si; Carroll, Michael

2003-03-01

The goal of the present work was to test the hypothesis that test frequency, f, does not have a statistically significant effect on the in vitro fatigue life of an acrylic bone cement. Uniaxial constant-amplitude tension-compression fatigue tests were conducted on 12 sets of cements, covering three formulations with three very different viscosities, two different methods of mixing the cement constituents, and two values of f (1 and 10 Hz). The test results (number of fatigue stress cycles, N(f)) were analyzed using the linearized form of the three-parameter Weibull equation, allowing the values of the Weibull mean (N(WM)) to be determined for each set. Statistical analysis of the lnN(f) data, together with an examination of the N(WM) estimates, showed support for the hypothesis over the range of f used. The principal use and explanation of the present finding are presented.

20. Fatigue Behaviour and Life Assessment of Jute-epoxy Composites under Tension-Tension Loading

Science.gov (United States)

Padmaraj, N. H.; Chethan, K. N.; Pavan; Onkar, Anand

2017-08-01

The present study involves fabrication and fatigue life assessment of multi-layered, woven jute fibres with epoxy matrix composites. Jute fabric were treated with 1N sodium hydroxidesolution for a duration of 6 hours. Alkali treatment was done to modify internal structure as well as surface properties of fibre. Laminates were fabricated by laying up multi layered woven jute fabric at varying angle [0-900/ (±450)2/0-900]. Vacuum bagging method was used to reduce the void content and thus increase the quality of composites. Tension-Tension fatigue tests were performed with a constant fatigue stress ratio (R=0.1) and results obtained from the tests were used to plot S-N Curve. A model based on power law equation was used for curve fitting.

1. Probabilistic Fatigue Life Updating for Railway Bridges Based on Local Inspection and Repair

Science.gov (United States)

Lee, Young-Joo; Kim, Robin E.; Suh, Wonho; Park, Kiwon

2017-01-01

Railway bridges are exposed to repeated train loads, which may cause fatigue failure. As critical links in a transportation network, railway bridges are expected to survive for a target period of time, but sometimes they fail earlier than expected. To guarantee the target bridge life, bridge maintenance activities such as local inspection and repair should be undertaken properly. However, this is a challenging task because there are various sources of uncertainty associated with aging bridges, train loads, environmental conditions, and maintenance work. Therefore, to perform optimal risk-based maintenance of railway bridges, it is essential to estimate the probabilistic fatigue life of a railway bridge and update the life information based on the results of local inspections and repair. Recently, a system reliability approach was proposed to evaluate the fatigue failure risk of structural systems and update the prior risk information in various inspection scenarios. However, this approach can handle only a constant-amplitude load and has limitations in considering a cyclic load with varying amplitude levels, which is the major loading pattern generated by train traffic. In addition, it is not feasible to update the prior risk information after bridges are repaired. In this research, the system reliability approach is further developed so that it can handle a varying-amplitude load and update the system-level risk of fatigue failure for railway bridges after inspection and repair. The proposed method is applied to a numerical example of an in-service railway bridge, and the effects of inspection and repair on the probabilistic fatigue life are discussed. PMID:28441768

2. Probabilistic Fatigue Life Updating for Railway Bridges Based on Local Inspection and Repair.

Science.gov (United States)

Lee, Young-Joo; Kim, Robin E; Suh, Wonho; Park, Kiwon

2017-04-24

Railway bridges are exposed to repeated train loads, which may cause fatigue failure. As critical links in a transportation network, railway bridges are expected to survive for a target period of time, but sometimes they fail earlier than expected. To guarantee the target bridge life, bridge maintenance activities such as local inspection and repair should be undertaken properly. However, this is a challenging task because there are various sources of uncertainty associated with aging bridges, train loads, environmental conditions, and maintenance work. Therefore, to perform optimal risk-based maintenance of railway bridges, it is essential to estimate the probabilistic fatigue life of a railway bridge and update the life information based on the results of local inspections and repair. Recently, a system reliability approach was proposed to evaluate the fatigue failure risk of structural systems and update the prior risk information in various inspection scenarios. However, this approach can handle only a constant-amplitude load and has limitations in considering a cyclic load with varying amplitude levels, which is the major loading pattern generated by train traffic. In addition, it is not feasible to update the prior risk information after bridges are repaired. In this research, the system reliability approach is further developed so that it can handle a varying-amplitude load and update the system-level risk of fatigue failure for railway bridges after inspection and repair. The proposed method is applied to a numerical example of an in-service railway bridge, and the effects of inspection and repair on the probabilistic fatigue life are discussed.

3. Prediction of Fatigue Life of Gear Subjected to Varying Loads

Directory of Open Access Journals (Sweden)

D. Hanumanna

1998-07-01

Full Text Available Structural members and components of a vehicle during service are subjected to varying loads which are random in nature. For structural members subjected to loads of constant amplitude, it is possible to describe the load with explicit mathematical relationship, and thereby, the life span can be estimated. Whereas, for structural members subjected to varying loads with time, there is no satisfactory method to estimate their life span. This paper describes a method for the estimation of life span of a gear in the gear box of a fighting vehicle subjected to fluctuating loads. For this purpose, it is assumed that the load spectrum corresponds to Gaussian (normal distribution, and the life has been worked out by applying linear cumulative damage theory.

4. Fatigue in Children With Sickle Cell Disease: Association With Neurocognitive and Social-Emotional Functioning and Quality of Life.

Science.gov (United States)

Anderson, Lindsay M; Allen, Taryn M; Thornburg, Courtney D; Bonner, Melanie J

2015-11-01

Children with sickle cell disease (SCD) report fatigue in addition to acute and chronic pain, which can decrease overall health-related quality of life (HRQL). The primary objective of the current study was to investigate the relationship between fatigue and HRQL. Given limited prior research, secondary objectives included investigation of associations between fatigue and functional outcomes, including child neurocognitive and social-emotional functioning. Children aged 8 to 16 years (N=32) and a caregiver completed measures of fatigue, HRQL, pain, and neurocognitive and social-emotional functioning. Controlling for pain and number of SCD-related hospitalizations, hierarchical linear regression models were used to determine the impact of child-reported and parent-reported fatigue on child HRQL. Correlational analyses were used to explore the relationship between fatigue and additional child outcomes. Data indicated that children with SCD experience clinically relevant levels of fatigue, which independently predicts lower HRQL. Fatigue was also associated with lower working memory, executive functioning, and higher levels of internalizing symptoms. Given its observed impact on HRQL and relationship to functional outcomes, fatigue may be an important target of clinical, home, or school interventions. This practice may attenuate the burden of fatigue in these patients, and in turn, help improve the quality of life of children living with SCD.

5. Fatigue, Sleep Quality, and Disability in Relation to Quality of Life in Multiple Sclerosis.

Science.gov (United States)

2015-01-01

Quality of life (QOL) is impaired in multiple sclerosis (MS) in part due to physical disability. MS-associated fatigue and poor sleep are common and treatable features of MS that affect QOL. We assessed the association between fatigue, sleep quality, and QOL in people with MS. Cross-sectional data were collected from 217 patients with MS. Health-related QOL (MS Quality of Life-54), fatigue (Fatigue Severity Scale [FSS]), and sleep quality (Pittsburgh Sleep Quality Inventory [PSQI]) were assessed. Expanded Disability Status Scale scores were also provided by a qualified neurologist. The mean ± SD age of the 217 patients was 32.6 ± 8.6 years, and 79% were female. One hundred fifty-two patients (70.0%) were classified as poor sleepers based on PSQI scores; 122 (56.2%) had significant fatigue based on FSS results. The mean ± SE physical (PCS) and mental (MCS) health composite scores of the MSQOL-54 were 40.12 ± 1.27 and 43.81 ± 1.61, respectively. There was a strong statistically significant positive correlation between PCS scores and MCS (r = 0.58), FSS (r = 0.49), and PSQI (r = 0.52) scores. MCS scores were strongly correlated with FSS (r = 0.53) and PSQI (r = 0.35) scores. Age exhibited statistically significant negative correlations with PCS (r = -0.21) and MCS (r = -0.58) scores, and was statistically significantly correlated with FSS (r = 0.23) and PSQI (r = 0.21) scores. Expanded Disability Status Scale scores were strongly correlated with FSS scores. These findings support screening of fatigue severity and sleep quality and their effects on QOL.

6. Fatigue, Sleep Quality, and Disability in Relation to Quality of Life in Multiple Sclerosis

Science.gov (United States)

2015-01-01

Background: Quality of life (QOL) is impaired in multiple sclerosis (MS) in part due to physical disability. MS-associated fatigue and poor sleep are common and treatable features of MS that affect QOL. We assessed the association between fatigue, sleep quality, and QOL in people with MS. Methods: Cross-sectional data were collected from 217 patients with MS. Health-related QOL (MS Quality of Life-54), fatigue (Fatigue Severity Scale [FSS]), and sleep quality (Pittsburgh Sleep Quality Inventory [PSQI]) were assessed. Expanded Disability Status Scale scores were also provided by a qualified neurologist. Results: The mean ± SD age of the 217 patients was 32.6 ± 8.6 years, and 79% were female. One hundred fifty-two patients (70.0%) were classified as poor sleepers based on PSQI scores; 122 (56.2%) had significant fatigue based on FSS results. The mean ± SE physical (PCS) and mental (MCS) health composite scores of the MSQOL-54 were 40.12 ± 1.27 and 43.81 ± 1.61, respectively. There was a strong statistically significant positive correlation between PCS scores and MCS (r = 0.58), FSS (r = 0.49), and PSQI (r = 0.52) scores. MCS scores were strongly correlated with FSS (r = 0.53) and PSQI (r = 0.35) scores. Age exhibited statistically significant negative correlations with PCS (r = −0.21) and MCS (r = −0.58) scores, and was statistically significantly correlated with FSS (r = 0.23) and PSQI (r = 0.21) scores. Expanded Disability Status Scale scores were strongly correlated with FSS scores. Conclusions: These findings support screening of fatigue severity and sleep quality and their effects on QOL. PMID:26664332

7. Quality of life in patients with multiple sclerosis in Turkey: relationship to depression and fatigue.

Science.gov (United States)

Tanriverdi, Derya; Okanli, Ayşe; Sezgin, Serap; Ekinci, Mine

2010-10-01

The purposes of this study were to assess the self-reported quality of life (QOL) in a group of Turkish patients with multiple sclerosis (MS) and to analyze whether the QOL was associated with fatigue and depression. The study used a descriptive design. A number of evaluation scales were administered to a study sample comprising 47 outpatients. The Short Form 36 for QOL, the Beck Depression Inventory for Depression, and the Visual Analogue Scale for Fatigue were used. The mean score for general QOL was 34.8 and indicated low QOL in MS patients. The results of our study have also shown that fatigue and depression strongly influence QOL in Turkish MS patients. Our findings may have important implications for the overall care of MS patients. The QOL of MS patients was affected negatively. Both fatigue and depression are common and treatable manifestations of MS, and these symptoms should be screened carefully in all MS patients. Care of MS patients requires the collaboration of all team members. Nurses have a key role as part of this team through the continuity of the care they provide and interaction with patients. Awareness of depression and fatigue can contribute to the nurses' ability to provide psychological support and enhance the QOL in MS patients.

8. Effect of Notch Location on Fatigue Life Prediction of Strength Mismatched HSLA Steel Weldments

Institute of Scientific and Technical Information of China (English)

S. Ravi; V. Balasubramanian; S. Nemat Nasser

2004-01-01

Welding of high strength low alloy steels (HSLA) involves usage of Iow, even and high strength filler materials (electrodes) than the parent material depending on the application of the welded structures and the availability of the filler material. In the present investigation, the fatigue crack growth behaviour of weld metal (WM) and heat affected zone (HAZ) regions of under matched (UM), equal matched (EM) and over matched (OM)joints has been studied. The base material used in this investigation is HSLA-80 steel of weldable grade. Shielded metal arc welding (SMAW) process has been used to fabricate the butt joints. Centre cracked tension (CCT) specimen has been used to evaluate the fatigue crack growth behaviour of the welded joints. Fatigue crack growth experiments have been conducted using servo hydraulic controlled fatigue testing machine at constant amplitude loading (R=0). A method has been proposed to predict the fatigue life of HSLA steel welds using fracture mechanics approach by incorporating influences of mismatch ratio (MMR) and notch location.

9. Relation Between Residual and Hoop Stresses and Rolling Bearing Fatigue Life

Science.gov (United States)

Oswald, Fred B.; Zaretsky, Erwin V.; Poplawski, Joseph V.

2015-01-01

Rolling-element bearings operated at high speed or high vibration may require a tight interference fit between the bore of the bearing and shaft to prevent rotation of the bearing bore around the shaft and fretting damage at the interfaces. Previous work showed that the hoop stresses resulting from tight interference fits can reduce bearing lives by as much as 65 percent. Where tight interference fits are required, case-carburized steel such as AISI 9310 or M50 NiL is often used because the compressive residual stresses inhibit subsurface crack formation and the ductile core inhibits inner-ring fracture. The presence of compressive residual stress and its combination with hoop stress also modifies the Hertz stress-life relation. This paper analyzes the beneficial effect of residual stresses on rolling-element bearing fatigue life in the presence of high hoop stresses for three bearing steels. These additional stresses were superimposed on Hertzian principal stresses to calculate the inner-race maximum shearing stress and the resulting fatigue life of the bearing. The load-life exponent p and Hertz stress-life exponent n increase in the presence of compressive residual stress, which yields increased life, particularly at lower stress levels. The Zaretsky life equation is described and is shown to predict longer bearing lives and greater load- and stress-life exponents, which better predicts observed life of bearings made from vacuum-processed steel.

10. Probability of Occurrence of Life-Limiting Fatigue Mechanism in P/M Nickel-Based Alloys (Postprint)

Science.gov (United States)

2016-03-30

AFRL-RX-WP-JA-2017-0146 PROBABILITY OF OCCURRENCE OF LIFE-LIMITING FATIGUE MECHANISM IN P/M NICKEL-BASED ALLOYS (POSTPRINT) M.J...February 2016 4. TITLE AND SUBTITLE PROBABILITY OF OCCURRENCE OF LIFE-LIMITING FATIGUE MECHANISM IN P/M NICKEL-BASED ALLOYS (POSTPRINT) 5a...paper, a micro structure-based model of the probability of occurrence of the minimum-lifetime, or the life-limiting, mechanism in powder processed Ni

11. Influence of specimen type and reinforcement on measured tension-tension fatigue life of unidirectional GFRP laminates

DEFF Research Database (Denmark)

Korkiakoski, Samuli; Brøndsted, Povl; Sarlin, Essi

2016-01-01

It is well known that standardised tension-tension fatigue test specimens of unidirectional (UD) glass-fibre-reinforced plastics (GFRP) laminates tend to fail at end tabs. The true fatigue life is then underestimated. The first objective of this study was to find for UD GFRP laminates a test...... specimen that fails in the gauge section. The second objective was to compare fatigue performance of two laminates, one having a newly developed UD powder-bound fabric as a reinforcement and the other having a quasi-UD stitched non-crimp fabric as a reinforcement. In the first phase, a rectangular specimen...... a significant effect on the failure mode and measured fatigue life of the laminates. A significantly higher fatigue life was measured for the laminate with the powder-bound fabric reinforcement when compared to the laminate with the stitched reinforcement....

12. Effect of beam oscillation on fatigue life of Ti-6Al-4V electron beam weldments

Energy Technology Data Exchange (ETDEWEB)

Babu, N. Kishore [Department of Metallurgical and Materials Engineering, IIT Madras, Chennai (India); Raman, S. Ganesh Sundara [Department of Metallurgical and Materials Engineering, IIT Madras, Chennai (India)], E-mail: ganesh@iitm.ac.in; Murthy, C. V. Srinivasa [Defence Research and Development Laboratory, Hyderabad (India); Reddy, G. Madhusudhan [Defence Metallurgical Research Laboratory, Hyderabad (India)

2007-12-15

The present study deals with the effect of beam oscillation technique using elliptical waveform on fatigue life of Ti-6Al-4V electron beam weldments. Autogenous full penetration bead-on-plate electron beam welds were made with and without beam oscillation. Some welds were subjected to post-weld heat treatment (PWHT) at two different temperatures (700 and 900 deg. C). Room temperature hardness, tensile properties and fatigue life of the weldments in the as-welded and PWHT conditions were studied and correlated with the microstructure. The beam oscillated weldments exhibited lower strength (hardness) compared to those made without beam oscillation. This was attributed to wider diffusional {alpha} plates in the beam oscillated welds due to lower cooling rates. The beam oscillated weldments exhibited inferior fatigue lives compared with unoscillated weldments owing to the presence of wider {alpha} platelets in the former. As the width of {alpha} platelets in the weldments subjected to PWHT at 700 deg. C was smaller than that in the weldments subjected to PWHT at 900 deg. C, they exhibited longer fatigue lives.

13. Substrate Creep on The Fatigue Life of A Model Dental Multilayer Structure

Energy Technology Data Exchange (ETDEWEB)

Zhou, J; Huang, M; Niu, X; soboyejo, W

2006-10-09

In this paper, we investigated the effects of substrate creep on the fatigue behavior of a model dental multilayer structure, in which a top glass layer was bonded to a polycarbonate substrate through a dental adhesive. The top glass layers were ground using 120 grit or 600 grit sand papers before bonding to create different sub-surface crack sizes and morphologies. The multilayer structures were tested under cyclic Hertzian contact loading to study crack growth and obtain fatigue life curves. The experiment results showed that the fatigue lives of the multilayer structures were impaired by increasing crack sizes in the sub-surfaces. They were also significantly reduced by the substrate creep when tested at relatively low load levels i.e. P{sub m} < 60 N (Pm is the maximum magnitude of cyclic load). But at relatively high load levels i.e. P{sub m} > 65 N, slow crack growth (SCG) was the major failure mechanisms. A modeling study was then carried out to explore the possible failure mechanisms over a range of load levels. It is found that fatigue life at relatively low load levels can be better estimated by considering the substrate creep effect (SCE).

14. Effects of prolonged fasting on fatigue and quality of life in patients with multiple sclerosis.

Science.gov (United States)

Etemadifar, Masoud; Sayahi, Farnaz; Alroughani, Raed; Toghianifar, Nafiseh; Akbari, Mojtaba; Nasr, Zahra

2016-06-01

Fasting is one of the recommended worships of several great religions in the world. During the month of Ramadan, circadian rhythm and pattern of eating changes result in physiological, biochemical and hormonal changes in the body. Many Muslims with medical conditions ask their physicians about the feasibility and safety of fasting during Ramadan. In this study, we aim to assess the effect of Ramadan fasting on the quality of life and fatigue in multiple sclerosis (MS) patients. Relapsing-remitting MS (RRMS) patients according to McDonald's criteria who had mild disability (EDSS score ≤3) were included in this study. Fatigue and quality of life were were assessed using the validated Persian versions of modified fatigue impact scale (MFIS) and multiple sclerosis quality of life-54 (MSQOL-54) questionnaires, respectively. 218 patients (150 females and 68 males) were enrolled in our study. There was no statistically significant difference between the mean total score of MSIF before and after fasting (25.50 ± 13.81 versus 26.94 ± 16.65; p = 0.58). The mean physical health and mental health composites of quality of life increased significantly after fasting (p = 0.008 and p = 0.003 respectively). Despite the observed lack of favorable effects on fatigue, our results showed increased quality of life of MS patients once Ramadan has ended. Whether this is specifically related to Ramadan-related fasting deserves further testing in appropriately designed larger prospective clinical studies.

15. Development of a probabilistic model for the prediction of fatigue life in the very high cycle fatigue (VHCF range based on inclusion population

Directory of Open Access Journals (Sweden)

Kolyshkin A.

2014-06-01

Full Text Available The VHCF behaviour of metallic materials containing microstructural defects such as non-metallic inclusions is determined by the size and distribution of the damage dominating defects. In the present paper, the size and location of about 60.000 inclusions measured on the longitudinal and transversal cross sections of AISI 304 sheet form a database for the probabilistic determination of failure-relevant inclusion distribution in fatigue specimens and their corresponding fatigue lifes. By applying the method of Murakami et al. the biggest measured inclusions were used in order to predict the size of failure-relevant inclusions in the fatigue specimens. The location of the crack initiating inclusions was defined based on the modeled inclusion population and the stress distribution in the fatigue specimen, using the probabilistic Monte Carlo framework. Reasonable agreement was obtained between modeling and experimental results.

16. Associations Between Fatigue and Disability, Functional Mobility, Depression, and Quality of Life in People with Multiple Sclerosis

Science.gov (United States)

Bush, Steffani; Gappmaier, Eduard

2016-01-01

Background: Fatigue is a common symptom in people with multiple sclerosis (MS), but its associations with disability, functional mobility, depression, and quality of life (QOL) remain unclear. We aimed to determine the associations between different levels of fatigue and disability, functional mobility, depression, and physical and mental QOL in people with MS. Methods: Eighty-nine individuals with MS (mean [SD] disease duration = 13.6 [9.8] years, mean [SD] Expanded Disability Status Scale [EDSS] score = 5.3 [1.5]) and no concurrent relapses were retrospectively analyzed. Participants were divided into two groups based on five-item Modified Fatigue Impact Scale (MFIS-5) scores: group LF (n = 32, MFIS-5 score ≤10 [low levels of fatigue]) and group HF (n = 57, MFIS-5 score >10 [high levels of fatigue]). Results: Sixty-four percent of the sample reported high levels of fatigue. Compared with group LF, group HF demonstrated significantly (P scale, and 12-item Multiple Sclerosis Walking Scale scores; depression; and QOL but not in the EDSS scores, which were not significantly different between groups. Conclusions: Fatigue was found to be a predominant symptom in the study participants. Individuals reporting higher levels of fatigue concomitantly exhibited greater impairments in functional mobility, depression, and physical and mental QOL. Disability was not found to be related to level of fatigue. These findings can be important for appropriate assessment and management of individuals with MS with fatigue. PMID:27134580

17. The Effect of Drive Signal Limiting on High Cycle Fatigue Life Analysis

Science.gov (United States)

Kihm, Frederic; Rizzi, Stephen A.

2014-01-01

It is common practice to assume a Gaussian distribution of both the input acceleration and the response when modeling random vibration tests. In the laboratory, however, shaker controllers often limit the drive signal to prevent high amplitude peaks. The high amplitudes may either be truncated at a given level (socalled brick wall limiting or abrupt clipping), or compressed (soft limiting), resulting in drive signals which are no longer Gaussian. The paper first introduces several methods for limiting a drive signal, including brick wall limiting and compression. The limited signal is then passed through a linear time-invariant system representing a device under test. High cycle fatigue life predictions are subsequently made using spectral fatigue and rainflow cycle counting schemes. The life predictions are compared with those obtained from unclipped input signals. Some guidelines are provided to help the test engineer decide how clipping should be applied under different test scenarios.

18. Fatigue life prediction of casing welded pipes by using the extended finite element method

Directory of Open Access Journals (Sweden)

Ljubica Lazić Vulićević

2016-03-01

Full Text Available The extended finite element (XFEM method has been used to simulate fatigue crack growth in casing pipe, made of API J55 steel by high-frequency welding, in order estimate its structural integrity and life. Based on the critical value of stress intensity factor KIc, measured in different regions of welded joint, the crack was located in the base metal as the region with the lowest resistance to crack initiation and propagation. The XFEM was first applied to the 3 point bending specimens to verify numerical results with the experimental ones. After successful verification, the XFEM was used to simulate fatigue crack growth, position axially in the pipe, and estimate its remaining life.

19. Random Amplitude Fatigue Life of Electroformed Nickel Micro-Channel Heat Exchanger Coupons

Directory of Open Access Journals (Sweden)

Larry Byrd

1998-01-01

Full Text Available The use of micro-channel heat exchangers (MCHEX with coolant flow passage diameters less than 1 mm has been proposed for heat flux, weight, or volume limited environments. This paper presents room temperature, random amplitude, ε − N (strain versus number of cycles to failure curves for MCHEX coupons formed by electroplating nickel on a suitable form. These coupons are unique in two aspects; the microstructure formed by electroplating and the presence of holes as an integral part of the structure. The hole diameters range from approximately 10% to 50% to the specimen thickness. The fatigue life of electroformed nickel can be estimated from constant amplitude data using the formulation presented. The heat exchangers with channels parallel to the coupon direction have a lower fatigue life than the solid material.

20. Space Shuttle Rudder Speed Brake Actuator-A Case Study Probabilistic Fatigue Life and Reliability Analysis

Science.gov (United States)

Oswald, Fred B.; Savage, Michael; Zaretsky, Erwin V.

2015-01-01

The U.S. Space Shuttle fleet was originally intended to have a life of 100 flights for each vehicle, lasting over a 10-year period, with minimal scheduled maintenance or inspection. The first space shuttle flight was that of the Space Shuttle Columbia (OV-102), launched April 12, 1981. The disaster that destroyed Columbia occurred on its 28th flight, February 1, 2003, nearly 22 years after its first launch. In order to minimize risk of losing another Space Shuttle, a probabilistic life and reliability analysis was conducted for the Space Shuttle rudder/speed brake actuators to determine the number of flights the actuators could sustain. A life and reliability assessment of the actuator gears was performed in two stages: a contact stress fatigue model and a gear tooth bending fatigue model. For the contact stress analysis, the Lundberg-Palmgren bearing life theory was expanded to include gear-surface pitting for the actuator as a system. The mission spectrum of the Space Shuttle rudder/speed brake actuator was combined into equivalent effective hinge moment loads including an actuator input preload for the contact stress fatigue and tooth bending fatigue models. Gear system reliabilities are reported for both models and their combination. Reliability of the actuator bearings was analyzed separately, based on data provided by the actuator manufacturer. As a result of the analysis, the reliability of one half of a single actuator was calculated to be 98.6 percent for 12 flights. Accordingly, each actuator was subsequently limited to 12 flights before removal from service in the Space Shuttle.

1. A Critical Plane-energy Model for Multiaxial Fatigue Life Prediction of Homogeneous and Heterogeneous Materials

Science.gov (United States)

Wei, Haoyang

A new critical plane-energy model is proposed in this thesis for multiaxial fatigue life prediction of homogeneous and heterogeneous materials. Brief review of existing methods, especially on the critical plane-based and energy-based methods, are given first. Special focus is on one critical plane approach which has been shown to work for both brittle and ductile metals. The key idea is to automatically change the critical plane orientation with respect to different materials and stress states. One potential drawback of the developed model is that it needs an empirical calibration parameter for non-proportional multiaxial loadings since only the strain terms are used and the out-of-phase hardening cannot be considered. The energy-based model using the critical plane concept is proposed with help of the Mroz-Garud hardening rule to explicitly include the effect of non-proportional hardening under fatigue cyclic loadings. Thus, the empirical calibration for non-proportional loading is not needed since the out-of-phase hardening is naturally included in the stress calculation. The model predictions are compared with experimental data from open literature and it is shown the proposed model can work for both proportional and non-proportional loadings without the empirical calibration. Next, the model is extended for the fatigue analysis of heterogeneous materials integrating with finite element method. Fatigue crack initiation of representative volume of heterogeneous materials is analyzed using the developed critical plane-energy model and special focus is on the microstructure effect on the multiaxial fatigue life predictions. Several conclusions and future work is drawn based on the proposed study.

2. The impact of disability, fatigue and sleep quality on the quality of life in multiple sclerosis

Directory of Open Access Journals (Sweden)

Ghaem Haleh

2008-01-01

Full Text Available Background: Only few papers have investigated the impact of multiple sclerosis (MS, especially MS-related fatigue and the impact of the quality of sleep on the quality of life (QoL in MS patients. Objective: The objective of this study was to measure the quality of life in MS patients and the impact of disability, fatigue and sleep quality, using statistical modeling. Materials and Methods: A cross-sectional study was conducted and data was collected from 141 MS patients, who were referred to the Mottahari Clinic, Shiraz, Iran, in 2005. Data on health-related quality of life (MSQoL-54, fatigue severity scale (FSS, and Pittsburgh sleep quality Index (PSQI were obtained in the case of all the patients. Epidemiology data concerning MS type, MS functional system score, expanded disability status scale (EDSS etc. were also provided by a qualified neurologist. Spearman a coefficient, Mann-Whitney U test, and linear regression model were used to analyze the data. Results : The mean ±SD age of 141 MS patients was 32.6±9.6 year. Thirty five (24.8% of them were male and the others were female. Eighty two (58.1% of the patients had EDSS score of ≤ 2, 36 (25.5% between 2.5 and 4.5, and 23 (16.3% ≥ 5. As per PSQI scores, two (1.4% of the patients had good sleep, 16 (11.3% had moderate sleep and 123 (87.2% had poor sleep. There was a significant high positive correlation between the quality of mental and physical health composite scores (r = 0.791, P < 0.001. There was a significant negative correlation between the quality of physical score and age (r = -0.88, P < 0.001, fatigue score (r = -0.640, P < 0.001, EDSS score (r = -0.476, P < 0.001 and PSQI (sleep quality r = -0.514, P < 0.000. Linear regression analysis showed that PSQI score, EDSS, and fatigue score were predictors in the model between the quality of physical score and covariates ( P < 0.001. Linear regression model showed that fatigue score and PSQI were predictors in the model between the

3. A New Energy-Critical Plane Damage Parameter for Multiaxial Fatigue Life Prediction of Turbine Blades

Directory of Open Access Journals (Sweden)

Zheng-Yong Yu

2017-05-01

Full Text Available As one of fracture critical components of an aircraft engine, accurate life prediction of a turbine blade to disk attachment is significant for ensuring the engine structural integrity and reliability. Fatigue failure of a turbine blade is often caused under multiaxial cyclic loadings at high temperatures. In this paper, considering different failure types, a new energy-critical plane damage parameter is proposed for multiaxial fatigue life prediction, and no extra fitted material constants will be needed for practical applications. Moreover, three multiaxial models with maximum damage parameters on the critical plane are evaluated under tension-compression and tension-torsion loadings. Experimental data of GH4169 under proportional and non-proportional fatigue loadings and a case study of a turbine disk-blade contact system are introduced for model validation. Results show that model predictions by Wang-Brown (WB and Fatemi-Socie (FS models with maximum damage parameters are conservative and acceptable. For the turbine disk-blade contact system, both of the proposed damage parameters and Smith-Watson-Topper (SWT model show reasonably acceptable correlations with its field number of flight cycles. However, life estimations of the turbine blade reveal that the definition of the maximum damage parameter is not reasonable for the WB model but effective for both the FS and SWT models.

4. Influences of fine pitch solder joint shape parameters on fatigue life under thermal cycle

Institute of Scientific and Technical Information of China (English)

HUANG Chun-yue; WU Zhao-hua; HUANG Hong-yan; ZHOU De-jian

2005-01-01

The solder joint reliability of a 0. 5 mm lead pitch, 240-pin quad flat package(QFP) was studied by nonlinear finite element analysis(FEA). The stress/strain distributions within the solder joints and the maximum plastic strain range of the solder joints were determined. Based on the calculated maximum plastic strain range the thermal fatigue life of the solder joints was calculated using Coffin-Manson equation. The influences of shape parameters including volume of solder joint, pad size and stand-off on the thermal fatigue life of the solder joints were also studied. The results show that the stress and strain distribution in the solder joint are not uniform; the interface between the lead and the solder joint is the high stress and strain region; the maximum stress and stain occur at the topmost point where the solder joint intersects with the inner side of the lead. The solder joint cracks should occur firstly at this point and propagate along the interface between the solder and the lead. The solder joint with the pad size of 1.25 mm× 0.35 mm, the stand-off of 0.02 mm and the solder volume of 0. 026 mm3 has longer fatigue life than that of any others. These optimal parameters have been applied in practice to assemble the 240-pin, 0.5 mm pitch QFP.

5. Fatigue criterion to system design, life and reliability: A primer

Science.gov (United States)

Zaretsky, Erwin V.

1992-01-01

A method for estimating a component's design survivability by incorporating finite element analysis and probabilistic material properties was developed. The method evaluates design parameters through direct comparisons of component survivability expressed in terms of Weibull parameters. The analysis was applied to a rotating disk with mounting bolt holes. The highest probability of failure occurred at, or near, the maximum shear stress region of the bolt holes. Distribution of material failure as a function of Weibull slope affects the probability of survival. Where Weibull parameters are unknown for a rotating disk, it may be permissible to assume Weibull parameters, as well as the stress-life exponent, in order to determine the qualitative effect of disk speed on the probability of survival.

6. Recent developments on SMA actuators: predicting the actuation fatigue life for variable loading schemes

Science.gov (United States)

Wheeler, Robert W.; Lagoudas, Dimitris C.

2017-04-01

Shape memory alloys (SMAs), due to their ability to repeatably recover substantial deformations under applied mechanical loading, have the potential to impact the aerospace, automotive, biomedical, and energy industries as weight and volume saving replacements for conventional actuators. While numerous applications of SMA actuators have been flight tested and can be found in industrial applications, these actuators are generally limited to non-critical components, are not widely implemented and frequently one-off designs, and are generally overdesigned due to a lack of understanding of the effect of the loading path on the fatigue life and the lack of an accurate method for predicting actuator lifetimes. In recent years, multiple research efforts have increased our understanding of the actuation fatigue process of SMAs. These advances can be utilized to predict the fatigue lives and failure loads in SMA actuators. Additionally, these prediction methods can be implemented in order to intelligently design actuators in accordance with their fatigue and failure limits. In the following paper, both simple and complex thermomechanical loading paths have been considered. Experimental data was utilized from two material systems: equiatomic Nickel-Titanium and Nickelrich Nickel-Titanium.

7. Experimental examination of fatigue life of welded joint with stress concentration

Directory of Open Access Journals (Sweden)

Miodrag Arsic

2016-03-01

Full Text Available This paper presents results of experimental examinations of stress concentration influence to fatigue life of butt welded joints with K-groove, produced from the most frequently used structural steel S355J2+N. One group of experiments comprised examinations carried out on the K-groove specimens with stress concentrators of edged notch type. Specimens with short cracks (limited length of initial crack, defined on the basis of the experience from fracture mechanics by the three points bending examinations, have been examined according to standard for the determination of S-N curve, and aimed to determine fatigue strengths for different lengths of initial crack and Relationship between fatigue strength and crack length. Other group of experiments comprised examinations of specimens with edge notch, prepared in accordance with ASTM E 399 for three points bending, in order to establish regularity between crack growth and range of exerted stress intensity factor aimed to determine resistance of welded joint to initial crack growth, namely fatigue threshold (ΔKth.

8. Effect of Intermittent Overload Cycles on Thermomechanical Fatigue Life of NiTi Shape Memory Alloy Wire

Science.gov (United States)

Saikrishna, C. N.; Ramaiah, K. V.; Vidyashankar, B.; Bhaumik, S. K.

2013-01-01

Effect of intermittent overload cycles on fatigue behavior of NiTi shape memory alloy wire during thermomechanical cycling (TMC) has been evaluated. Results showed that fatigue life of NiTi is enhanced when the intermittent overload is above certain minimum level. An enhancement in fatigue life by ~50 pct is observed when the overload ratio is 2.0. Accumulation of plastic strain in the material under such TMC condition is found to be relatively high compared to that of TMC with no overload cycles.

9. Laser Peening and Shot Peening Effects on Fatigue Life and Surface Roughness of Friction Stir Welded 7075-T7351 Aluminum

Science.gov (United States)

Hatamleh, Omar; Lyons, Jed; Forman, Royce

2006-01-01

The effects of laser peening, shot peening, and a combination of both on the fatigue life of Friction Stir Welds (FSW) was investigated. The fatigue samples consisted of dog bone specimens and the loading was applied in a direction perpendicular to the weld direction. Several laser peening conditions with different intensities, durations, and peening order were tested to obtain the optimum peening parameters. The surface roughness resulting from various peening techniques was assessed and characterized. The results indicate a significant increase in fatigue life using laser peening compared to shot peened versus their native welded specimens.

10. Research of weld joint fatigue life of the AlMgSi07.F25 aluminium alloy under bending-torsion cyclic loading

Directory of Open Access Journals (Sweden)

M. Vaško

2017-01-01

Full Text Available The contribution deals with a research into the fatigue life of weld joints of AlMgSi07.F25 aluminium alloy. The paper will present unique biaxial testing equipment, process of preparation of specimen rods for fatigue tests, and the results of fatigue life assessment for the aluminium alloy during cyclic bending-torsion loading. Fatigue tests under constant amplitude loading were performed on a special electromechanical machine with a suitable clamping system. The obtained fatigue curves were compared with the most widely-known fatigue criteria such as LIU, F-S and B-M.

11. The effect of coating residual stress on the fatigue life of thermal spray-coated steel and aluminum

Energy Technology Data Exchange (ETDEWEB)

McGrann, R.T.R.; Greving, D.J.; Shadley, J.R.; Rybicki, E.F. [Tulsa Univ., OK (United States). Mechanical Engineering Dept.; Kruecke, T.L.; Bodger, B.E. [Southwest Aeroservice, Inc., Tulsa, OK (United States)

1998-10-10

The acceptance of thermal spray coatings in many applications depends on the effect of the coating on the fatigue performance of the coated part. One of the factors that influences the fatigue life of thermal spray-coated components is the residual stress in the coating. This study investigates the fatigue performance of tungsten carbide-cobalt (WC-Co) thermal spray coating systems. Bending fatigue tests of specimens with WC-Co coatings on both 4130 steel substrates and 6061 aluminum substrates were conducted. The through-thickness residual stress level in the thermal spray coatings was determined using the modified layer removal method. The effect of the residual stresses on the fatigue life of the coated specimens was analyzed. It was found that there is a direct relation between the residual stress in the coating and the fatigue life of the coated part. Fatigue life can be changed by a factor of ten due to the level of compressive residual stress in the coating. (orig.) 7 refs.

12. Fatigue in high speed aluminium craft: Evaluating a design methodology for estimating the fatigue life using large scale tests and full scale trials

NARCIS (Netherlands)

Drummen, I.; Schiere, M.; Tuitman, J.T.

2013-01-01

Within the VOMAS project, a methodology has been developed to estimate the fatigue life of high-speed aluminium crafts. This paper presents the large scale test and full scale trials which were done to acquire data for evaluating the developed methodology and presents results of this evaluation. Dur

13. Effect of stress ratio on long life fatigue behavior of Ti-Al alloy under flexural loading

Institute of Scientific and Technical Information of China (English)

XUE Hong-qian; TAO Hua; SHAO Ren-ping; B.CLAUDE

2008-01-01

A new ultrasonic three-point bending fatigue test device was introduced to investigate fatigue life ranging up to 1010 cycles and associated fracture behavior of Ti-Al alloy. Tests were performed at a frequency of 20kHz with stress ratio R=0.5 and R=0.7 at ambient temperature in air. Three groups of specimens with different surface roughness were applied to investigate the effect of surface roughness on fatigue life. Furthermore, optical microscopy (OM) and scanning electron microscopy (SEM) were used for microstructure characteristic and fracture surface analysis. The S-N curves obtained show that fatigue failure occurs in the range of 105-1010 cycles, and the asymptote of S-N curve inclines slightly in very high cycle regime, but is not horizontal for R=0.5. Fatigue limit appears after 108 cycles for R=0.7. Surface roughness (the maximum roughness is no more than 3μm) has no influence on the fatigue properties in the high cycle regime. A detailed investigation on fatigue fracture surface shows that the Ti-Al alloy studied here is a binary alloy in the microstructure composed of α2-Ti3Al and γ-Ti-Al with fully lamellar microstructure. Fractography shows that fatigue failures are mostly initiated on the surface of specimens, also, in very high cycle regime, subsurface fatigue crack initiation can be found. Interlamellar fatigue crack initiation is predominant in the Ti-Al alloy with fully lamellar structure. Fatigue crack growth is mainly in transgranular mode.

14. The effect of ply folds as manufacturing defect on the fatigue life of CFRP materials

Directory of Open Access Journals (Sweden)

S. Hörrmann

2016-10-01

Full Text Available Manufacturing defects are inherent to any manufacturing process. However, in composite materials they might be unavoidable, e.g. ply waviness or even folds of plies are present in complex shaped parts during high pressure resin transfer molding of carbon fiber reinforced polymers. In this work, the effect of the ply folds on the fatigue life of the composite material is investigated. Folds along fiber direction (as they commonly appear during manufacturing were artificially introduced in unidirectional non crimp fabric plies. The target of this study is the prediction of damage initiation due to this particular type of manufacturing defect. The folds locally increase the fiber volume fraction and also introduce resin rich areas. Fatigue tests in fiber direction and transverse to fiber direction are performed at different load ratios under constant amplitude loading. The influence of the defect geometry on damage initiation and progression is investigated at different scales by non-destructive methods before testing, continuous strain measurement and monitoring the damage progression during testing and fractography analysis after final failure. Most of the time, the first damage was observed at the location of the introduced fold for all considered load cases. However, it was also found, that the folds lead to no significant reduction in fatigue life

15. An all-in-one numerical methodology for fretting wear and fatigue life assessment

Directory of Open Access Journals (Sweden)

I. Llavori

2016-07-01

Full Text Available Many mechanical components such as, bearing housings, flexible couplings and spines or orthopedic devices are simultaneously subjected to a fretting wear and fatigue damage. For this reason, the combined study on a single model of wear, crack initiation and propagation is of great interest. This paper presents an all-in-one 2D cylinder on flat numerical model for life assessment on coupled fretting wear and fatigue phenomena. In the literature, two stages are usually distinguished: crack nucleation and its subsequent growth. The method combines the Archard wear model, a critical-plane implementation of the Smith-Watson- Topper (SWT multiaxial fatigue criterion coupled with the Miner-Palmgren accumulation damage rule for crack initiation prediction. Then, the Linear Elastic Fracture Mechanics (LEFM via eXtended Finite Element Method (X-FEM embedded into the commercial finite element code Abaqus FEA has been employed to determine the crack propagation stage. Therefore, the sum of the two stages gives a total life prediction. Finally, the numerical model was validated with experimental data reported in the literature and a good agreement was obtained.

16. The influence of applied heat-treatment on in 718 fatigue life at three point flexural bending

Directory of Open Access Journals (Sweden)

J. Belan

2017-01-01

Full Text Available The Inconel alloy 718 is an iron-nickel based superalloy with a working temperature up to 650 °C. Presented phases such as γ'' (Ni3Nb, γ' (Ni3Al, and δ (delta – Ni3Nb are responsible for the alloy's unique properties. The δ – delta phase is profitable when situated at grain boundaries in small quantities due to increasing fatigue life. However, at temperatures close to 650 °C the γ'' transforms to δ – delta and causes a decrease in fatigue life. Heat-treatment (800°C/ for 72 hours and its influence on fatigue life are discussed in this paper. Fatigue tests were carried out at room temperature. After the tests we plotted the S-N curves for both stages. SEM (Scanning Electron Microscopy fractography was carried out as well.

17. Cryogenic Tensile Strength and Fatigue Life of Carbon Nanotube Multi-Yarn.

Science.gov (United States)

Misak, H E; Mall, S

2016-03-01

Carbon nanotube (CNT) multi-yarns, consisting of 30 yarns, were tested under monotonic tensile load and fatigue at the room temperature (298 K) and two cryogenic temperatures (232 and 123 K). Tensile stiffness increased with the decrease of temperature. The average ultimate tensile strength was higher at 123 K when compared to the higher temperatures (232 and 298 K). Failure mechanism changed from a combination of classical variant and independent fiber breakage at the two higher temperatures to mostly classical variant failure mechanism at the lower temperature. The CNT-yarn's fatigue life also increased with decreasing temperature. CNT-yarns have been shown to function well at lower temperatures making them usable for applications requiring operation at cryogenic temperatures, such as in satellites and high altitude aircraft.

18. Factors affecting the corrosion fatigue life in nickel based superalloys for disc applications

Directory of Open Access Journals (Sweden)

Rosier Hollie

2014-01-01

Full Text Available The nickel based superalloy 720Li is employed in the gas turbine due to its mechanical performance at elevated temperature. A comprehensive assessment of the materials behaviour under representative service conditions is reported to address the drive for ever increasing temperatures and more arduous environmental exposure. Fatigue experiments have been performed in an air and air/SOx environment at 700 ∘C containing a mixed salt as a contaminant. There is an intimate relationship between local salt level (flux, stress level and stress state, i.e. static or cyclic. The interaction with these variables with the work hardened layer present on the surface of all tested specimens as a result of the shot peening process directly affects the crack initiation process. If specific conditions of environment and stress are achieved, a significant reduction in fatigue life is observed.

19. Reconstruction of probabilistic S-N curves under fatigue life following lognormal distribution with given confidence

Institute of Scientific and Technical Information of China (English)

ZHAO Yong-xiang; YANG Bing; PENG Jia-chun

2007-01-01

When the historic probabilistic S-N curves are given under special survival probability and confidence levels and there is no possible to re-test, fatigue reliability analysis at other levels can not be done except for the special levels. Therefore, the wide applied curves are expected. Monte Carlo reconstruction methods of the test data and the curves are investigated under fatigue life following lognormal distribution. To overcome the non-conservative assessment of existent man-made enlarging the sample size up to thousands, a simulation policy is employed to address the true production where the sample size is controlled less than 20 for material specimens, 10 for structural component specimens and the errors matching the statistical parameters are less than 5 percent. Availability and feasibility of the present methods have been indicated by the reconstruction practice of the test data and curves for 60Si2Mn high strength spring steel of railway industry.

20. Influence of the Inclusion Shape on the Rolling Contact Fatigue Life of Carburized Steels

Science.gov (United States)

Neishi, Yutaka; Makino, Taizo; Matsui, Naoki; Matsumoto, Hitoshi; Higashida, Masashi; Ambai, Hidetaka

2013-05-01

It has been well known that the flaking failure in rolling contact fatigue (RCF) originates from nonmetallic inclusions in steels, and their apparent size is one of the important factors affecting RCF life. However, the influence of inclusion shape on the RCF life has not been fully clarified. In this study, attention was paid to the influence of the inclusion shape on the RCF life. This was evaluated by using carburized JIS-SCM420 (SAE4320) steels that contained two different shapes of MnS—stringer type and spheroidized type—as inclusions. Sectional observations were made to investigate the relation between the occurrence of shear crack in the subsurface and the shape of MnS. It was found that the RCF life was well correlated with the length of MnS projected to the load axis, and the initiation of shear crack in subsurface was accelerated as the length of MnS increased.

1. Effects of zinc supplementation on fatigue and quality of life in patients with colorectal cancer.

Science.gov (United States)

Ribeiro, Sofia Miranda de Figueiredo; Braga, Camila Bitu Moreno; Peria, Fernanda Maris; Martinez, Edson Zangiacomi; Rocha, José Joaquim Ribeiro da; Cunha, Selma Freire Carvalho

2017-01-01

To investigate the effects of oral zinc supplementation on fatigue intensity and quality of life of patients during chemotherapy for colorectal cancer. A prospective, randomized, double-blinded, placebo-controlled study was conducted with 24 patients on chemotherapy for colorectal adenocarcinoma in a tertiary care public hospital. The study patients received zinc capsules 35mg (Zinc Group, n=10) or placebo (Placebo Group, n=14) orally, twice daily (70mg/day), for 16 weeks, from the immediate postoperative period to the fourth chemotherapy cycle. Approximately 45 days after surgical resection of the tumor, all patients received a chemotherapeutic regimen. Before each of the four cycles of chemotherapy, the Functional Assessment of Chronic Illness Therapy-Fatigue scale was completed. We used a linear mixed model for longitudinal data for statistical analysis. The scores of quality of life and fatigue questionnaires were similar between the groups during the chemotherapy cycles. The Placebo Group presented worsening of quality of life and increased fatigue between the first and fourth cycles of chemotherapy, but there were no changes in the scores of quality of life or fatigue in the Zinc Group. Zinc supplementation prevented fatigue and maintained quality of life of patients with colorectal cancer on chemotherapy. Investigar os efeitos da suplementação oral de zinco sobre a intensidade da fadiga e a qualidade de vida de pacientes durante a quimioterapia para neoplasia colorretal. Estudo prospectivo, randomizado, controlado e duplo-cego conduzido em um hospital universitário público terciário, com 24 pacientes em regime quimioterápico para adenocarcinoma colorretal. Os pacientes receberam cápsulas de zinco 35mg (Grupo Zinco, n=10) ou placebo (Grupo Placebo, n=14) por via oral, duas vezes ao dia (70mg/dia), durante 16 semanas, desde o período pós-operatório imediato até o quarto ciclo de quimioterapia. Todos os pacientes receberam quimioterapia por

2. Slow Crack Growth and Fatigue Life Prediction of Ceramic Components Subjected to Variable Load History

Science.gov (United States)

2001-01-01

Present capabilities of the NASA CARES/Life (Ceramic Analysis and Reliability Evaluation of Structures/Life) code include probabilistic life prediction of ceramic components subjected to fast fracture, slow crack growth (stress corrosion), and cyclic fatigue failure modes. Currently, this code has the capability to compute the time-dependent reliability of ceramic structures subjected to simple time-dependent loading. For example, in slow crack growth (SCG) type failure conditions CARES/Life can handle the cases of sustained and linearly increasing time-dependent loads, while for cyclic fatigue applications various types of repetitive constant amplitude loads can be accounted for. In real applications applied loads are rarely that simple, but rather vary with time in more complex ways such as, for example, engine start up, shut down, and dynamic and vibrational loads. In addition, when a given component is subjected to transient environmental and or thermal conditions, the material properties also vary with time. The objective of this paper is to demonstrate a methodology capable of predicting the time-dependent reliability of components subjected to transient thermomechanical loads that takes into account the change in material response with time. In this paper, the dominant delayed failure mechanism is assumed to be SCG. This capability has been added to the NASA CARES/Life (Ceramic Analysis and Reliability Evaluation of Structures/Life) code, which has also been modified to have the ability of interfacing with commercially available FEA codes executed for transient load histories. An example involving a ceramic exhaust valve subjected to combustion cycle loads is presented to demonstrate the viability of this methodology and the CARES/Life program.

3. Influence of surface treatments on fatigue life of a two-stroke free piston linear engine component using random loading

Institute of Scientific and Technical Information of China (English)

RAHMAN M.M.; ARIFFIN A.K.; JAMALUDIN N.; HARON C.H.C.

2006-01-01

This paper describes the finite element (FE) analysis technique to predict fatigue life using the narrow band frequency response approach. The life prediction results are useful for improving the component design methodology at the very early development stage. The approach is found to be suitable for a periodic loading but requires very large time records to accurately describe random loading processes. This paper is aimed at investigating the effects of surface treatments on the fatigue life of the free piston linear engine's components. Finite element modelling and frequency response analysis were conducted using computer aided design and finite element analysis commercial codes, respectively. In addition, the fatigue life prediction was carried out using finite element based fatigue analysis commercial code. Narrow band approach was specially applied to predict the fatigue life of the free piston linear engine cylinder block. Significant variation was observed between the surface treatments and untreated cylinder block of free piston engine. The obtained results indicated that nitrided treatment yielded the longest life. This approach can determine premature products failure phenomena, and therefore can reduce time to market, improve product reliability and customer confidence.

4. Fatigue life determination by damage measuring in SAE 8620 specimens steel subjected to multiaxial experiments in neutral and corrosive environment

Energy Technology Data Exchange (ETDEWEB)

Silva, Luiz L. da; Filho, Nelson do N.A.; Gomes, Paulo de T.V.; Rabello, Emerson G.; Mansur, Tanius R., E-mail: silvall@cdtn.br, E-mail: nnaf@cdtn.br, E-mail: ptvg@cdtn.br, E-mail: egr@cdtn.br, E-mail: tanius@cdtn.br [Centro de Desenvolvimento da Tencologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

2013-07-01

Fatigue is the fail phenomenon of a material subjected to cyclic loads. This phenomenon affects any component under loads (forces, temperatures, etc.) that changes in time. When there is a combined load, originating multiaxial fatigue, which is the most of the real loads, worst is the situation. Before the component fail, the fatigue phenomenon produces damages to its material and this is a cumulative process that could not be reduced. In the continuum mechanic context, material damage is defined as a parameter that reduces the component resistance and this could cause its fail. The process of damage measuring by changes in electrical resistance is used in this work, and from experimental results of SAE 8620 steel specimens subjected to multiaxial fatigue in corrosive and neutral environment, the remaining specimen time life could be determined. Each specimen has its initial electrical resistance measured and after a certain number of fatigue cycles stopping points, its electrical resistance was measured again. In order to study multiaxial fatigue in specimens, a machine that induces simultaneously bending and torsional loads in the specimen was developed. Air at the temperature range of 18 deg C and 20 deg C was considered neutral environment. The corrosive environment was a NaCl solution with a concentration of 3,5% in weigh. The experimental results showed that the measuring fatigue damage using the changes in electrical resistance is efficient and that is possible to estimate the effect of a corrosive environment in the fatigue damage. (author)

5. A model for life predictions of nickel-base superalloys in high-temperature low cycle fatigue

Science.gov (United States)

Romanoski, Glenn R.; Pelloux, Regis M.; Antolovich, Stephen D.

1988-01-01

Extensive characterization of low-cycle fatigue damage mechanisms was performed on polycrystalline Rene 80 and IN100 tested in the temperature range from 871 to 1000 C. Low-cycle fatigue life was found to be dominated by propagation of microcracks to a critical size governed by the maximum tensile stress. A model was developed which incorporates a threshold stress for crack extension, a stress-based crack growth expression, and a failure criterion. The mathematical equivalence between this mechanistically based model and the strain-life low-cycle fatigue law was demonstrated using cyclic stress-strain relationships. The model was shown to correlate the high-temperature low-cycle fatigue data of the different nickel-base superalloys considered in this study.

6. A critical analysis of the Mises stress criterion used in frequency domain fatigue life prediction

Directory of Open Access Journals (Sweden)

2016-10-01

Full Text Available Multiaxial fatigue failure criteria are formulated in time and frequency domain. The number of frequency domain criteria is rather small and the most popular one is the equivalent von Mises stress criterion. This criterion was elaborated by Preumont and Piefort on the basis of well-known von Mises stress concept, first proposed by Huber in 1907, and well accepted by the scientific community and engineers. It is important to know, that the criterion was developed to determine the yield stress and material effort under static load. Therefore the direct use of equivalent von Mises stress criterion for fatigue life prediction can lead to some incorrectness of theoretical and practical nature. In the present study four aspects were discussed: influence of the value of fatigue strength of tension and torsion, lack of parallelism of the SN curves, abnormal behaviour of the criterion under biaxial tensioncompression and influence of phase shift between particular stress state components. Information contained in this article will help to prevent improper use of this criterion and contributes to its better understanding

7. CARES/Life Ceramics Durability Evaluation Software Enhanced for Cyclic Fatigue

Science.gov (United States)

Nemeth, Noel N.; Powers, Lynn M.; Janosik, Lesley A.

1999-01-01

The CARES/Life computer program predicts the probability of a monolithic ceramic component's failure as a function of time in service. The program has many features and options for materials evaluation and component design. It couples commercial finite element programs--which resolve a component's temperature and stress distribution--to reliability evaluation and fracture mechanics routines for modeling strength-limiting defects. The capability, flexibility, and uniqueness of CARES/Life have attracted many users representing a broad range of interests and has resulted in numerous awards for technological achievements and technology transfer. Recent work with CARES/Life was directed at enhancing the program s capabilities with regards to cyclic fatigue. Only in the last few years have ceramics been recognized to be susceptible to enhanced degradation from cyclic loading. To account for cyclic loads, researchers at the NASA Lewis Research Center developed a crack growth model that combines the Power Law (time-dependent) and the Walker Law (cycle-dependent) crack growth models. This combined model has the characteristics of Power Law behavior (decreased damage) at high R ratios (minimum load/maximum load) and of Walker law behavior (increased damage) at low R ratios. In addition, a parameter estimation methodology for constant-amplitude, steady-state cyclic fatigue experiments was developed using nonlinear least squares and a modified Levenberg-Marquardt algorithm. This methodology is used to give best estimates of parameter values from cyclic fatigue specimen rupture data (usually tensile or flexure bar specimens) for a relatively small number of specimens. Methodology to account for runout data (unfailed specimens over the duration of the experiment) was also included.

8. Fatigue (PDQ)

Science.gov (United States)

... of daily living . Better quality of life . More satisfaction with life. A greater sense of well-being. ... and decrease fatigue. The importance of eating enough food and drinking enough fluids. Physical therapy for patients ...

9. Strength and fatigue life evaluation of composite laminate with embedded sensors

Science.gov (United States)

Rathod, Vivek T.; Hiremath, S. R.; Roy Mahapatra, D.

2014-04-01

Prognosis regarding durability of composite structures using various Structural Health Monitoring (SHM) techniques is an important and challenging topic of research. Ultrasonic SHM systems with embedded transducers have potential application here due to their instant monitoring capability, compact packaging potential toward unobtrusiveness and noninvasiveness as compared to non-contact ultrasonic and eddy current techniques which require disassembly of the structure. However, embedded sensors pose a risk to the structure by acting as a flaw thereby reducing life. The present paper focuses on the determination of strength and fatigue life of the composite laminate with embedded film sensors like CNT nanocomposite, PVDF thin films and piezoceramic films. First, the techniques of embedding these sensors in composite laminates is described followed by the determination of static strength and fatigue life at coupon level testing in Universal Testing Machine (UTM). Failure mechanisms of the composite laminate with embedded sensors are studied for static and dynamic loading cases. The coupons are monitored for loading and failure using the embedded sensors. A comparison of the performance of these three types of embedded sensors is made to study their suitability in various applications. These three types of embedded sensors cover a wide variety of applications, and prove to be viable in embedded sensor based SHM of composite structures.

10. An inverse method for online stress monitoring and fatigue life analysis of boiler drums

Institute of Scientific and Technical Information of China (English)

HU Wen-sen; LI Bin; CAO Zi-dong; YANG Dong; LI Ya-chao

2009-01-01

A method based on solution of the inverse heat conduction problem was presented for online stress monitoring and fatigue life analysis of boiler drums. The mathematical model of the drum temperature distribution is based on the assumptions that the difference of temperature along the longitudinal axis of the boiler drum is negligible with changes only in the radial direction and the circumferential direction, and that the outer surface of drum is thermally insulated. Combining this model with the control-volume method provides temperatures at different points on a eross-section of the drum. With the temperature data, the stresses and the life expectancy of the boiler drum are derived according to the ASME code. Applying this method to the cold start-up process of a 300 MW boiler demonswated the absence of errors caused by the boundary condition assumptions on the inner surface of the drum and testified that the method is an applicable technique for the online stress monitoring and fatigue life analysis of boiler drums.

11. Fatigue life assessment of cardiovascular balloon-expandable stents: a two-scale plasticity-damage model approach.

Science.gov (United States)

Argente dos Santos, H A F; Auricchio, F; Conti, M

2012-11-01

Cardiovascular disease has become a major global health care problem in the present decade. To tackle this problem, the use of cardiovascular stents has been considered a promising and effective approach. Numerical simulations to evaluate the in vivo behavior of stents are becoming more and more important to assess potential failures. As the material failure of a stent device has been often associated with fatigue issues, as a result of the high number of cyclic loads these devices are subjected to in vivo, numerical approaches for fatigue life assessment of stents has gained special interest in the engineering community. Numerical fatigue predictions can be used to modify the design and prevent failure, without making and testing numerous physical devices, thus preventing from undesired fatigue failures. This work presents a fatigue life numerical method for the analysis of cardiovascular balloon-expandable stainless steel stents. The method is based on a two-scale continuum damage mechanics model in which both plasticity and damage mechanisms are assumed to take place at a scale smaller than the scale of the representative volume element. The fatigue failure criterion is based on the Soderberg relation. The method is applied to the fatigue life assessment of both PalmazShatz and Cypher stent designs. Validation of the method is performed through comparison of the obtained numerical results with some experimental results available for the PalmazShatz stent design. The present study gives also possible directions for future research developments in the framework of the numerical fatigue life assessment of real balloon-expandable stents.

12. Fatigue life prediction of casing welded pipes by using the extended finite element method

OpenAIRE

2016-01-01

The extended finite element (XFEM) method has been used to simulate fatigue crack growth in casing pipe, made of API J55 steel by high-frequency welding, in order estimate its structural integrity and life. Based on the critical value of stress intensity factor KIc, measured in different regions of welded joint, the crack was located in the base metal as the region with the lowest resistance to crack initiation and propagation. The XFEM was first applied to the 3 point bending specimens to...

13. Reducing Uncertainty in Fatigue Life Limits of Turbine Engine Alloys (Preprint)

Science.gov (United States)

2012-08-01

Calcaterra, M.L. Dent, M.M. Derriso , W.J. Hardman, J.W. Jones, S.M. Russ, Materials Damage Prognosis - Proceedings of a Symposium of the Materials Science and... Derriso , W.J. Hardman, J. Wayne Jones, S.M. Rusa (Eds.), New Orleans, LA, 2005, pp. 343-350. [24] S.K. Jha, M.J. Caton, J.M. Larsen, Mean vs. life...ultrasonic fatigue, in: J.M. Larsen, L. Christodoulou, J.R. Calcaterra, M.L. Dent, M.M. Derriso , W.J. Hardman, J. Wayne Jones, S.M. Rusa (Eds.), New

14. Advanced Failure Determination Measurement Techniques Used in Thermal Fatigue Life Testing of Electronic Packaging

Science.gov (United States)

Wallace, A. P.; Cornford, S. L.; Gross, M. A.

1996-01-01

Thermal fatigue life testing of various electronic packaging technologies is being performed by the Reliability Technology Group at the Jet Propulsion Laboratory. These testing efforts are in progress to improve uderstanding of the reliability issues associated with low volume packaging technologies for space applications and to develop qualification and acceptance approaches for these technologies. The work described here outlines the electrical failure detection techniques used during testing by documenting the circuits and components used to make these measurements, the sensitivity of the measurements, and the applicability of each specific measurement.

15. Low Cycle Fatigue Behavior of 316LN Stainless Steel Alloyed with Varying Nitrogen Content. Part II: Fatigue Life and Fracture Behavior

Science.gov (United States)

Prasad Reddy, G. V.; Sandhya, R.; Sankaran, S.; Mathew, M. D.

2014-10-01

Influence of nitrogen content on low cycle fatigue life and fracture behavior of 316LN stainless steel (SS) alloyed with 0.07 to 0.22 wt pct nitrogen is presented in this paper over a range of total strain amplitudes ( ±0.25 to 1.0 pct) in the temperature range from 773 K to 873 K (500 °C to 600 °C). The combined effect of nitrogen and strain amplitude on fatigue life is observed to be complex i.e., fatigue life either decreases/increases with increase in nitrogen content or saturates/peaks at 0.14 wt pct N depending on strain amplitude and temperature. Coffin-Manson plots (CMPs) revealed both single-slope and dual-slope strain-life curves depending on the test temperature and nitrogen content. 316LN SS containing 0.07 and 0.22 wt pct N showed nearly single-slope CMP at all test temperatures, while 316LN SS with 0.11 and 0.14 wt pct N exhibited marked dual-slope behavior at 773 K (500 °C) that changes to single-slope behavior at 873 K (600 °C). The changes in slope of CMP are found to be in good correlation with deformation substructural changes.

16. Effect of Progressive Muscle Relaxation on the Fatigue and Quality of Life Among Iranian Aging Persons.

Science.gov (United States)

Hassanpour-Dehkordi, Ali; Jalali, Amir

2016-07-01

Since the elderly population is increasing rapidly in developing countries which may decrease the physical activity and exercise and in turn could affect the elderly's quality of life, this study aimed to investigate the effect of progressive muscle relaxation on the elderly's quality of life in Iran. In a randomized clinical trial, participants were randomly divided into intervention and control groups. For the intervention group, muscular progressive relaxation was run three days per week for three months (totally 36 sessions). In relaxation, a patient contract a group of his/her muscles in each step and relaxes them after five seconds and finally loosens all muscles and takes five deep breaths. Each session lasts for 45 minutes. The instrument of data gathering consisted of questionnaires on individual's demographic data and quality of life SF-36. After intervention, quality of life increased significantly in the patients undergoing muscular progressive relaxation and fatigue severity decreased significantly in the intervention group compared to prior to intervention. In addition, there was a statistically significant difference in mean score of physical performance, restricted activity after physical problem, energy, socially function, physical pain, overall hygiene, and quality of life between intervention and control groups. By implementing regular and continuous progressive muscle relaxation, quality of life could be increased in different dimensions in the elderly and the context could be provided to age healthily and enjoy higher health and autonomy. Therefore, all of the therapeutic staffs are recommended to implement this plan to promote the elderly's quality of life.

17. Modelling the Strength and Fatigue Life of a Unidirectional Fibrous Composite by Using Daniels' Sequence and Markov Chains

Science.gov (United States)

Paramonov, Yu.; Cimanis, V.; Varickis, S.; Kleinhofs, M.

2013-11-01

A review of the previous works of the authors dedicated to the use of Daniels' sequence (DS) for analyzing the relation between the distribution of the static strength of components of a unidirectional fibrous composite (UFC) and the distribution of its fatigue life is presented. A generalization of the DS which can be used to analyze the association of distribution of the static strength of composite components with distribution of the static strength of the UFC itself is given. In analyzing the fatigue life of a UFC, unlike in Daniels' model, the loading rate and randomness of the number of still workable components in the weak microvolume in which the destruction process takes place are taken into account. By analyzing the fatigue life, it is possible to explain the existence of the random fatigue strength and to calculate the maximum load at which the probability of absence of fatigue failure is great enough when the number of cycles of fatigue loading tends to infinity. Numerical examples of processing of experimental data are presented, and estimates for parameters of the corresponding nonlinear regression model, which can be interpreted as the strength parameters of UFC, are obtained.

18. Surface fatigue life and failure characteristics of EX-53, CBS 1000M, and AISI 9310 gear materials

Science.gov (United States)

Townsend, D. P.

1985-01-01

Spur gear endurance tests and rolling-element surface fatigue tests are conducted to investigate EX-53 and CBS 1000M steels for use as advanced application gear materials, to determine their endurance characteristics, and to compare the results with the standard AISI 9310 gear material. The gear pitch diameter is 8.89 cm (3.50 in). Gear test conditions are an oil inlet temperature of 320 K (116 F), an oil outlet temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), and a speed of 10,000 rpm. Bench-type rolling-element fatigue tests are conducted at ambient temperature with a bar specimen speed of 12,500 rpm and a maximum Hertz stress of 4.83 GPa (700 ksi). The EX-53 test gears have a surface fatigue life of twice that of the AISI 9310 spur gears. The CBS 1000M test gears have a surface fatigue life of more than twice that of the AISI 9310 spur gears. However, the CBS 1000M gears experience a 30-percent tooth fracture failure which limits its use as a gear material. The rolling-contact fatigue lines of RC bar specimens of EX-53 and ASISI 9310 are approximately equal. However, the CBS 1000M RC specimens have a surface fatigue life of about 50 percent that of the AISI 9310.

19. Averaged strain energy density-based synthesis of crack initiation life in notched steel bars under torsional fatigue

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Filippo Berto

2016-10-01

Full Text Available The torsional fatigue behaviour of circumferentially notched specimens made of austenitic stainless steel, SUS316L, and carbon steel, SGV410, characterized by different notch root radii has been recently investigated by Tanaka. In that contribution, it was observed that the total fatigue life of the austenitic stainless steel increases with increasing stress concentration factor for a given applied nominal shear stress amplitude. By using the electrical potential drop method, Tanaka observed that the crack nucleation life was reduced with increasing stress concentration, on the other hand the crack propagation life increased. The experimental fatigue results, originally expressed in terms of nominal shear stress amplitude, have been reanalysed by means of the local strain energy density (SED averaged over a control volume having radius R0 surrounding the notch tip. To exclude all extrinsic effects acting during the fatigue crack propagation phase, such as sliding contact and/or friction between fracture surfaces, crack initiation life has been considered in the present work. In the original paper, initiation life was defined in correspondence of a 0.1÷0.4-mm-deep crack. The control radius R0 for fatigue strength assessment of notched components, thought of as a material property, has been estimated by imposing the constancy of the averaged SED for both smooth and cracked specimens at NA = 2 million loading cycles

20. The effect of plasma electrolytic oxidation on the mean stress sensitivity of the fatigue life of the 6082 aluminum alloy

Science.gov (United States)

Winter, L.; Morgenstern, R.; Hockauf, K.; Lampke, T.

2016-03-01

In this work the mean stress influence on the high cycle fatigue behavior of the plasma electrolytic oxidized (PEO) 6082 aluminum alloy (AlSi1MgMn) is investigated. The present study is focused on the fatigue life time and the susceptibility of fatigue-induced cracking of the oxide coating and their dependence on the applied mean stress. Systematic work is done comparing conditions with and without PEO treatment, which have been tested using three different load ratios. For the uncoated substrate the cycles to failure show a significant dependence on the mean stress, which is typical for aluminum alloys. With increased load ratio and therefore increased mean stress, the fatigue strength decreases. The investigation confirms the well-known effect of PEO treatment on the fatigue life: The fatigue strength is significantly reduced by the PEO process, compared to the uncoated substrate. However, also the mean stress sensitivity of the fatigue performance is reduced. The fatigue limit is not influenced by an increasing mean stress for the PEO treated conditions. This effect is firstly shown in these findings and no explanation for this effect can be found in literature. Supposedly the internal compressive stresses and the micro-cracks in the oxide film have a direct influence on the crack initiation and growth from the oxide film through the interface and in the substrate. Contrary to these findings, the susceptibility of fatigue-induced cracking of the oxide coating is influenced by the load ratio. At tension-tension loading a large number of cracks, which grow partially just in the aluminum substrate, are present. With decreasing load ratio to alternating tension-compression stresses, the crack number and length increases and shattering of the oxide film is more pronounced due to the additional effective compressive part of the load cycle.

1. A Methodology to Predict Uniform Material Fatigue Life of Cast Iron： Law for Cast Iron%A Methodology to Predict Uniform Material Fatigue Life of Cast Iron： Law for Cast Iron

Institute of Scientific and Technical Information of China (English)

Sinan Korkmaz

2011-01-01

Mechanical, physical and manufacturing properties of east iron make it attractive for many fields of application, such as cranks and cylinder holds. As in design of all metals, fatigue life prediction is an intrinsic part of the design process of structural sections that are made of cast iron. A methodology to predict high-cycle fatigue life of cast iron is proposed. Stress amplitude-strain amplitude, strain amplitude-number of loading cycles relationships of cast iron are investigated. Also, fatigue life prediction in terms of Smith, Watson and Topper parameter is carried out using the proposed method. Results indicate that the analytical outcomes of the proposed methodology are in good accordance with the experimental data for the two studied types of cast iron： EN-GJS-400 and EN-GJS-600.

2. Oxidation and the Effects of High Temperature Exposures on Notched Fatigue Life of an Advanced Powder Metallurgy Disk Superalloy

Science.gov (United States)

Sudbrack, Chantal K.; Draper, Susan L.; Gorman, Timothy T.; Telesman, Jack; Gab, Timothy P.; Hull, David R.

2012-01-01

Oxidation and the effects of high temperature exposures on notched fatigue life were considered for a powder metallurgy processed supersolvus heat-treated ME3 disk superalloy. The isothermal static oxidation response at 704 C, 760 C, and 815 C was consistent with other chromia forming nickel-based superalloys: a TiO2-Cr2O3 external oxide formed with a branched Al2O3 internal subscale that extended into a recrystallized - dissolution layer. These surface changes can potentially impact disk durability, making layer growth rates important. Growth of the external scales and dissolution layers followed a cubic rate law, while Al2O3 subscales followed a parabolic rate law. Cr- rich M23C6 carbides at the grain boundaries dissolved to help sustain Cr2O3 growth to depths about 12 times thicker than the scale. The effect of prior exposures was examined through notched low cycle fatigue tests performed to failure in air at 704 C. Prior exposures led to pronounced debits of up to 99 % in fatigue life, where fatigue life decreased inversely with exposure time. Exposures that produced roughly equivalent 1 m thick external scales at the various isotherms showed statistically equivalent fatigue lives, establishing that surface damage drives fatigue debit, not exposure temperature. Fractographic evaluation indicated the failure mode for the pre-exposed specimens involved surface crack initiations that shifted with exposure from predominately single intergranular initiations with transgranular propagation to multi-initiations from the cracked external oxide with intergranular propagation. Weakened grain boundaries at the surface resulting from the M23C6 carbide dissolution are partially responsible for the intergranular cracking. Removing the scale and subscale while leaving a layer where M23C6 carbides were dissolved did not lead to a significant fatigue life improvement, however, also removing the M23C6 carbide dissolution layer led to nearly full recovery of life, with a

3. Evaluation method of multiaxial low cycle fatigue life for cubic single crystal material

Institute of Scientific and Technical Information of China (English)

CHEN Jiping; DING Zhiping

2007-01-01

The coupling effect of normal stress and shear stress on orthotropic materials happens when applied loading deflects from the directions of the principal axes of the material coordinate system.By taking account of the coupling effects,formulas of equivalent stress and strain for cubic single crystal materials are cited.Using the equivalent strain and equivalent stress for such material and a variable k,which is introduced to express the effect of asymmetrical cyclic loading on fatigue life,a low cycle fatigue (LCF) life prediction model for such material in multiaxial stress starts is proposed.On the basis of the yield criterion and constitutive model of cubic single crystal materials,a subroutine to calculate the thermo elastic-plastic stress-strain of the material on an ANSYS platform was developed.The cyclic stress-strain of DD3 notched specimens under asymmetrical loading at 680℃ was analyzed.Low cycle fatigue test data of the single crystal nickel-based superalloy are used to fit the different parameters of the power law with multiple linear regression analysis.The equivalent stress and strain for a cubic single crystal material as failure parameters have the largest correlation coefficient.A power law exists between k and the failure cycle.The model was validated with LCF test data of CMSX-2 and DD3 single crystal nickel-based superalloys.All the test data fall into the factor of 2.5 for CMSX-2 hollow cylinder specimens and 2.0 scatter band for DD3 notched specimens,respectively.

4. Bending Resistance and Cyclic Fatigue Life of Reciproc, Unicone, and WaveOne Reciprocating Instruments.

Science.gov (United States)

Silva, Emmanuel João Nogueira Leal; Villarino, Laise Silva; Vieira, Victor Talarico Leal; Accorsi-Mendonça, Thais; Antunes, Henrique Dos Santos; De-Deus, Gustavo; Lopes, Hélio Pereira

2016-12-01

This study evaluated the bending resistance and cyclic fatigue life of a new single-file reciprocating instrument (Unicone; Medin, Nové Město na Moravě, Czech Republic). Reciproc (VDW, Munich, Germany) and WaveOne (Dentsply Maillefer) instruments were used as references for comparison. Flexibility was determined by 45° bending tests using a universal testing machine. The cyclic fatigue test was performed using a custom-made device. For this test, an artificial canal with a 60° angle and a 5-mm radius of curvature was used. Scanning electron microscopic analysis was performed to determine the mode of fracture and possible deformations at the helical shaft. Statistical analysis for the bending resistance test was performed using parametric methods (ie, 1-way analysis of variance). Post hoc pair-wise comparisons were performed using the Tukey test for multiple comparisons (P bending resistance than the other tested systems (P  .05). When mean life was compared among the brands, Reciproc lasted longer than WaveOne with a probability of 99.9%, longer than Unicone in the "RECIPROC ALL" mode with a probability of 99.9%, and longer than Unicone in the "WAVEONE ALL" mode with a probability of 99.9% (all statistically significant). Moreover, WaveOne lasted longer than Unicone in the "RECIPROC ALL" mode with a probability of 98.5% and longer than Unicone in the "WAVEONE ALL" mode with a probability of 99.8% (all statistically significant). Finally, Unicone in the "RECIPROC ALL" mode lasted longer than Unicone in the "WAVEONE ALL" mode with a probability of 95.3% (statistically significant). The new reciprocating instrument Unicone showed lower cyclic fatigue resistance compared with Reciproc R25 and WaveOne Primary files. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

5. Dynamic additional loads influencing the fatigue life of gears in an electric vehicle transmission

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G.Belingardi

2014-10-01

Full Text Available In recent years the implementation of the electric engine in the automotive industries has been increasingly marked. The speed of the electric motors is much higher than the combustion engine ones, bringing transmission gears to be subjected to high dynamic loads. For this reason the dynamic effects on fatigue life of these components have be taken into account in a more careful way respect to what is done with the usual gears. In the present work the overload effects due to both speed and meshing in a gear couple of an electric vehicle transmission have been analyzed. The electric vehicle is designed for urban people mobility and presents all the requirements to be certified as M1 vehicle (a weight less than 600 kg and a maximum speed more than 90 Km/h. To investigate the overload effects of teeth in contact, the reference gear design Standards (ISO 6336 introduce a specific multiplicative factor to the applied load called Internal Dynamic Factor (Kv. Aim of this work is to evaluate how dynamic overloads may influence the fatigue life of the above quoted gears in term of durability. To this goal, Kv values have been calculated by means of the analytical equations (ISO 6336 Methods B and C and then they have been compared with the results coming from multibody simulations, involving full rigid and rigid-flexible models.

6. Verification of recursive probabilistic integration (RPI) method for fatigue life management using non-destructive inspections

Science.gov (United States)

Chen, Tzikang J.; Shiao, Michael

2016-04-01

This paper verified a generic and efficient assessment concept for probabilistic fatigue life management. The concept is developed based on an integration of damage tolerance methodology, simulations methods1, 2, and a probabilistic algorithm RPI (recursive probability integration)3-9 considering maintenance for damage tolerance and risk-based fatigue life management. RPI is an efficient semi-analytical probabilistic method for risk assessment subjected to various uncertainties such as the variability in material properties including crack growth rate, initial flaw size, repair quality, random process modeling of flight loads for failure analysis, and inspection reliability represented by probability of detection (POD). In addition, unlike traditional Monte Carlo simulations (MCS) which requires a rerun of MCS when maintenance plan is changed, RPI can repeatedly use a small set of baseline random crack growth histories excluding maintenance related parameters from a single MCS for various maintenance plans. In order to fully appreciate the RPI method, a verification procedure was performed. In this study, MC simulations in the orders of several hundred billions were conducted for various flight conditions, material properties, and inspection scheduling, POD and repair/replacement strategies. Since the MC simulations are time-consuming methods, the simulations were conducted parallelly on DoD High Performance Computers (HPC) using a specialized random number generator for parallel computing. The study has shown that RPI method is several orders of magnitude more efficient than traditional Monte Carlo simulations.

7. A Novel Creep-Fatigue Life Prediction Model for P92 Steel on the Basis of Cyclic Strain Energy Density

Science.gov (United States)

Ji, Dongmei; Ren, Jianxing; Zhang, Lai-Chang

2016-09-01

A novel creep-fatigue life prediction model was deduced based on an expression of the strain energy density in this study. In order to obtain the expression of the strain energy density, the load-controlled creep-fatigue (CF) tests of P92 steel at 873 K were carried out. Cyclic strain of P92 steel under CF load was divided into elastic strain, applying and unloading plastic strain, creep strain, and anelastic strain. Analysis of cyclic strain indicates that the damage process of P92 steel under CF load consists of three stages, similar to pure creep. According to the characteristics of the strains above, an expression was defined to describe the strain energy density for each cycle. The strain energy density at stable stage is inversely proportional to the total strain energy density dissipated by P92 steel. However, the total strain energy densities under different test conditions are proportional to the fatigue life. Therefore, the expression of the strain energy density at stable stage was chosen to predict the fatigue life. The CF experimental data on P92 steel were employed to verify the rationality of the novel model. The model obtained from the load-controlled CF test of P92 steel with short holding time could predict the fatigue life of P92 steel with long holding time.

8. A Novel Creep-Fatigue Life Prediction Model for P92 Steel on the Basis of Cyclic Strain Energy Density

Science.gov (United States)

Ji, Dongmei; Ren, Jianxing; Zhang, Lai-Chang

2016-11-01

A novel creep-fatigue life prediction model was deduced based on an expression of the strain energy density in this study. In order to obtain the expression of the strain energy density, the load-controlled creep-fatigue (CF) tests of P92 steel at 873 K were carried out. Cyclic strain of P92 steel under CF load was divided into elastic strain, applying and unloading plastic strain, creep strain, and anelastic strain. Analysis of cyclic strain indicates that the damage process of P92 steel under CF load consists of three stages, similar to pure creep. According to the characteristics of the strains above, an expression was defined to describe the strain energy density for each cycle. The strain energy density at stable stage is inversely proportional to the total strain energy density dissipated by P92 steel. However, the total strain energy densities under different test conditions are proportional to the fatigue life. Therefore, the expression of the strain energy density at stable stage was chosen to predict the fatigue life. The CF experimental data on P92 steel were employed to verify the rationality of the novel model. The model obtained from the load-controlled CF test of P92 steel with short holding time could predict the fatigue life of P92 steel with long holding time.

9. Uniaxial and Multiaxial Fatigue Life Prediction of the Trabecular Bone Based on Physiological Loading: A Comparative Study.

Science.gov (United States)

Fatihhi, S J; Harun, M N; Abdul Kadir, Mohammed Rafiq; Abdullah, Jaafar; Kamarul, T; Öchsner, Andreas; Syahrom, Ardiyansyah

2015-10-01

Fatigue assessment of the trabecular bone has been developed to give a better understanding of bone properties. While most fatigue studies are relying on uniaxial compressive load as the method of assessment, in various cases details are missing, or the uniaxial results are not very realistic. In this paper, the effect of three different load histories from physiological loading applied on the trabecular bone were studied in order to predict the first failure surface and the fatigue lifetime. The fatigue behaviour of the trabecular bone under uniaxial load was compared to that of multiaxial load using a finite element simulation. The plastic strain was found localized at the trabecular structure under multiaxial load. On average, applying multiaxial loads reduced more than five times the fatigue life of the trabecular bone. The results provide evidence that multiaxial loading is dominated in the low cycle fatigue in contrast to the uniaxial one. Both bone volume fraction and structural model index were best predictors of failure (p < 0.05) in fatigue for both types of loading, whilst uniaxial loading has indicated better values in most cases.

10. Influence of Working Environment on Fatigue Life Time Duration for Runner Blades of Kaplan Turbines

Directory of Open Access Journals (Sweden)

Ana-Maria Budai

2010-10-01

Full Text Available The paper present an analytical analyzes refer to influence of working environment on life time duration in service of runner blades of Kaplan turbines. The study are made using only analytical method, the entry dates being obtained from measurements made in situ for a Kaplan turbine. To calculate the maximum number of stress cycles whereupon the runner blades work without any damage it was used an analytical relation known in specialized literatures under the name of Morrow’s relation. To estimate fatigue life time duration will be used a formula obtained from one of most common cumulative damage methodology taking in consideration the real exploitation conditions of a specified Kaplan turbine.

11. An equivalent strain/Coffin-Manson approach to multiaxial fatigue and life prediction in superelastic Nitinol medical devices.

Science.gov (United States)

Runciman, Amanda; Xu, David; Pelton, Alan R; Ritchie, Robert O

2011-08-01

Medical devices, particularly endovascular stents, manufactured from superelastic Nitinol, a near-equiatomic alloy of Ni and Ti, are subjected to complex mixed-mode loading conditions in vivo, including axial tension and compression, radial compression, pulsatile, bending and torsion. Fatigue lifetime prediction methodologies for Nitinol, however, are invariably based on uniaxial loading and thus fall short of accurately predicting the safe lifetime of stents under the complex multiaxial loading conditions experienced physiologically. While there is a considerable body of research documented on the cyclic fatigue of Nitinol in uniaxial tension or bending, there remains an almost total lack of comprehensive fatigue lifetime data for other loading conditions, such as torsion and tension/torsion. In this work, thin-walled Nitinol tubes were cycled in torsion at various mean and alternating strains to investigate the fatigue life behavior of Nitinol and results compared to equivalent fatigue data collected under uniaxial tensile/bending loads. Using these strain-life results for various loading modes and an equivalent referential (Lagrangian) strain approach, a strategy for normalizing these data is presented. Based on this strategy, a fatigue lifetime prediction model for the multiaxial loading of Nitinol is presented utilizing a modified Coffin-Manson approach where the number of cycles to failure is related to the equivalent alternating transformation strain.

12. The effect of lubricating oils on bearing fatigue-life using the Evonik RohMax pitting test procedure

Energy Technology Data Exchange (ETDEWEB)

2009-07-01

A major requirement for modern driveline lubricants is the need to reduce churning losses and friction in order to deliver continual improvements in fuel efficiency. In trying to achieve this oil formulators target lower and lower viscosities, testing the limits of what is acceptable Churning loss reductions are being made by reducing the viscosity of the lubricating oil. Reduced oil viscosities can lead to reduced oil film thicknesses, especially at high operating temperatures. Thinner oil films can lead to an increase in friction, and a decrease in the fatigue-life capacity in lubricated contacts of bearings and gears in several driveline applications. Extensive fluid testing is required. Current test procedures are subject to extremely high variability, and large numbers of experiments are required to develop high confidence in the test conclusions. This publication introduces a new fatigue-life test method, which in our hands provides a clear improvement in test time, cost, and reproducibility. The test's results enable an estimation of the effect of lubricating oils on bearing fatigue-life. This is done by comparing the results to those obtained with reference oils which have also been tested in the standardized bearing tests for lubricating oils. The effects of operating parameters on test accuracy and repeatability have been studied. The parameters studied are oil temperature, contact pressure, speed and the test specimen batch. In addition to the measurement of bearing fatigue-life, the new test may also be used to study gear fatigue-life. We have used this test to investigate the lubrication oils' influence on fatigue-life in bearings and in gears. In order to extend the comparisons to gear performance the reference fluids were evaluated in standard industry test procedures used for determining gear performance, in particular the FZG test rig, thus establishing an extra insight in the fluids' performance by comparing gear test performance

13. Effects of a home-based exercise program on quality of life, fatigue, and depression in patients with ankylosing spondylitis.

Science.gov (United States)

Durmus, Dilek; Alayli, Gamze; Cil, Erhan; Canturk, Ferhan

2009-04-01

The aim of this trial was to investigate the effects of a 12-week home-based exercise program (HEP) on quality of life (QOL) and fatigue in patients with Ankylosing Spondylitis (AS). Forty-three patients with AS were included in this study. Group 1 was given a HEP; Group 2 served as the control group. The functional capacity (Bath Ankylosing Spondylitis Functional Index), disease activity (Bath Ankylosing Spondylitis Disease Assessment Index), fatigue (Multidimensional Assessment of Fatigue Scale), depression (Beck Depression Inventory scores), and QOL (Short Form 36) of all participants were evaluated. There were significant improvements for all the parameters in two groups after the treatment. The improvements for all the parameters were better in the exercise group than in the control group. Home-based exercise programs are very effective in improving QOL and reducing fatigue. Because of these advantages, HEP should be advised for the management program in AS in addition to medical treatments.

14. Microstructures and fatigue life of SnAgCu solder joints bearing Nano-Al particles in QFP devices

Science.gov (United States)

Zhang, Liang; Fan, Xi-ying; Guo, Yong-huan; He, Cheng-wen

2014-05-01

Microstructures and fatigue life of SnAgCu and SnAgCu bearing nano-Al particles in QFP (Quad flat package) devices were investigated, respectively. Results show that the addition of nano-Al particles into SnAgCu solder can refine the microstructures of matrix microstructure. Moreover, the nano-Al particles present in the solder matrix, act as obstacles which can create a back stress, resisting the motion of dislocations. In QFP device, it is found that the addition of nano-Al particles can increase the fatigue life by 32% compared with the SnAgCu solder joints during thermal cycling loading.

15. Analytical Method to Estimate Fatigue Life Time Duration in Service for Runner Blade Mechanism of Kaplan Turbines

Directory of Open Access Journals (Sweden)

Ana – Maria Budai

2010-10-01

Full Text Available The paper present an analytical method that can be used to determianted fatigue life time duration in service for runner blade mechanism of Kaplan turbines. The study was made for lever button of runer blade mechanism using two analytical relation to calculate the maximum number of stress cycles whereupon the mechanism work without any damage. To estimate fatigue life time duration will be used a formula obtained from one of most comon cumulative damage methodology taking in consideration the real exploatation conditions of a specified Kapaln turbine.

16. Microstructural Influence on Deformation and Fatigue Life of Composites Using the Generalized Method of Cells

Science.gov (United States)

Arnold, S. M.; Murthy, P.; Bednarcyk, B. A.; Pineda, E. J.

2015-01-01

A fully coupled deformation and damage approach to modeling the response of composite materials and composite laminates is presented. It is based on the semi-­-analytical generalized method of cells (GMC) micromechanics model as well as its higher fidelity counterpart, HFGMC, both of which provide closed-form constitutive equations for composite materials as well as the micro scale stress and strain fields in the composite phases. The provided constitutive equations allow GMC and HFGMC to function within a higher scale structural analysis (e.g., finite element analysis or lamination theory) to represent a composite material point, while the availability of the micro fields allow the incorporation of lower scale sub­-models to represent local phenomena in the fiber and matrix. Further, GMC's formulation performs averaging when applying certain governing equations such that some degree of microscale field accuracy is surrendered in favor of extreme computational efficiency, rendering the method quite attractive as the centerpiece in a integrated computational material engineering (ICME) structural analysis; whereas HFGMC retains this microscale field accuracy, but at the price of significantly slower computational speed. Herein, the sensitivity of deformation and the fatigue life of graphite/epoxy PMC composites, with both ordered and disordered microstructures, has been investigated using this coupled deformation and damage micromechanics based approach. The local effects of fiber breakage and fatigue damage are included as sub-models that operate on the microscale for the individual composite phases. For analysis of laminates, classical lamination theory is employed as the global or structural scale model, while GMC/HFGMC is embedded to operate on the microscale to simulate the behavior of the composite material within each laminate layer. A key outcome of this study is the statistical influence of microstructure and micromechanics idealization (GMC or HFGMC) on

17. Small Crack Growth and Fatigue Life Predictions for High-Strength Aluminium Alloys. Part 1; Experimental and Fracture Mechanics Analysis

Science.gov (United States)

Wu, X. R.; Newman, J. C.; Zhao, W.; Swain, M. H.; Ding, C. F.; Phillips, E. P.

1998-01-01

The small crack effect was investigated in two high-strength aluminium alloys: 7075-T6 bare and LC9cs clad alloy. Both experimental and analytical investigations were conducted to study crack initiation and growth of small cracks. In the experimental program, fatigue tests, small crack and large crack tests A,ere conducted under constant amplitude and Mini-TWIST spectrum loading conditions. A pronounced small crack effect was observed in both materials, especially for the negative stress ratios. For all loading conditions, most of the fatigue life of the SENT specimens was shown to be crack propagation from initial material defects or from the cladding layer. In the analysis program, three-dimensional finite element and A weight function methods were used to determine stress intensity factors and to develop SIF equations for surface and corner cracks at the notch in the SENT specimens. A plastisity-induced crack-closure model was used to correlate small and large crack data, and to make fatigue life predictions, Predicted crack-growth rates and fatigue lives agreed well with experiments. A total fatigue life prediction method for the aluminum alloys was developed and demonstrated using the crack-closure model.

18. Exercise Interventions to Reduce Cancer-Related Fatigue and Improve Health-Related Quality of Life in Cancer Patients.

Science.gov (United States)

Scott, Kelly; Posmontier, Bobbie

Cancer-related fatigue (CRF) is the most common and debilitating side effect of patients receiving treatment of cancer. It is reported that 60% to 100% of patients will develop CRF as a result of the treatment or the cancer itself. The effects last for years posttreatment and lower overall quality of life. The purpose of this integrative review was to determine whether exercise interventions could reduce CRF and improve overall health-related quality of life (HRQOL) among selected cancer patients. Clinical Key, ProQuest Nursing and Allied Health Source, Cochrane Library, Mosby's Nursing Consult, and MEDLINE (Ovid) were the databases searched. Key terms searched were fatigue, exercise, cancer fatigue, holistic, spiritual, quality of life, and prevention. Findings from most studies suggest that exercise can decrease the effects of CRF among cancer patients, leading to an overall improved HRQOL. No negative results on the effects of exercise on CRF were reported. Nurses can be instrumental in developing holistic multidisciplinary exercise programs to assist in the management of CRF and improve HRQOL among cancer patients during and after cancer treatment. Recommendations for future research include the need for larger study sample sizes, a universal definition of fatigue, determination of the best exercise regimens, more consistent fatigue measures to facilitate better comparison across studies, and specifically assess patient improvements in overall mental and spiritual well-being within a holistic framework.

19. Effect of hardening induced by cold expansion on damage fatigue accumulation and life assessment of Aluminum alloy 6082 T6

Directory of Open Access Journals (Sweden)

Bendouba Mostefa

2012-12-01

Full Text Available Hole cold expansion (HCE is an effective method to extend the fatigue life of mechanical structures. During cold expansion process compressive residual stresses around the expanded hole are generated. The enhancement of fatigue life and the crack initiation and growth behavior of a holed specimen were investigated by using the 6082 Aluminum alloy. The present study suggests a simple technical method for enhancement of fatigue life by a cold expansion hole of pre-cracked specimen. Fatigue damage accumulation of cold expanded hole in aluminum alloy which is widely used in transportation and in aeronautics was analyzed. Experimental tests were carried out using pre-cracked SENT specimens. Tests were performed in two and four block loading under constant amplitude. These tests were performed by using two and four blocks under uniaxial constant amplitude loading. The increasing and decreasing loading were carried. The experimental results were compared to the damage calculated by the Miner's rule and a new simple fatigue damage indicator. This comparison shows that the 'damaged stress model', which takes into account the loading history, yields a good estimation according to the experimental results. Moreover, the error is minimized in comparison to the Miner's model.

20. Pre-crack fatigue life assessment of relevant aircraft materials using fractal analysis of eddy current test data

Science.gov (United States)

Schreiber, Jürgen; Cikalova, Ulana; Hillmann, Susanne; Meyendorf, Norbert; Hoffmann, Jochen

2013-01-01

Successful determination of residual fatigue life requires a comprehensive understanding of the fatigue related material deformation mechanism. Neither macroscopic continuum mechanics nor micromechanic observations provide sufficient data to explain subsequent deformation structures occurring during the fatigue life of a metallic structure. Instead mesomechanic deformation on different scaling levels can be studied by applying fractal analysis of various means of nondestructive inspection measurements. The resulting fractal dimension data can be correlated to the actual material damage states, providing an estimation of the remaining residual fatigue life before macroscopic fracture develops. Recent efforts were aimed to apply the fractal concept to aerospace relevant materials AA7075-T6 and Ti-6Al-4V. Proven and newly developed fractal analysis methods were applied to eddy current (EC) measurements of fatigued specimens, with the potential to transition this approach to an aircraft for an in-situ nondestructive inspection. The occurrence of mesomechanic deformation at the material surface of both AA7075-T6 and Ti-6Al-4V specimens could be established via topography images using confocal microscopy (CM). Furthermore, a pulsed eddy current (PEC) approach was developed, combined with a sophisticated new fractal analysis algorithm based on short pulse excitation and evaluation of EC relaxation behavior. This paper presents concept, experimental realization, fractal analysis procedures, and results of this effort.

1. Analysis of Fatigue Crack Growth in Longitudinals of Ship Hull and Fatigue Life%船体纵骨疲劳裂纹扩展及寿命分析

Institute of Scientific and Technical Information of China (English)

何文涛; 刘敬喜; 解德

2015-01-01

Based on ABAQUS in python scripting language, and combined with virtual crack closure technique, a program (FCG-System) is developed to simulate the growth of fatigue crack. The crack in a typical longitudinal connection of an oil tanker is simulated. Crack growth path and fatigue life is discussed under lateral pressure load and axial tension load respectively. Results indicate that crack growth paths are different under these two load conditions and the fatigue lives before the fractures of face-plate occupy a large proportion in total life.%基于有限元软件 ABAQUS，结合虚拟裂纹闭合法、裂纹扩展判据及子结构技术，应用脚本语言 Python开发了模拟疲劳裂纹扩展的程序(FCG-System)。对含初始裂纹的油船纵骨节点疲劳裂纹扩展进行数值模拟，并探讨侧向压力和轴向拉力这两种载荷对疲劳裂纹扩展路径和疲劳寿命的影响。结果表明，两种加载方式下裂纹扩展路径不同，且面板断裂前的疲劳寿命在总寿命中占据很大的成分。

2. Investigation of Cumulative Fatigue Damage Through Sequential Low Cycle Fatigue and High Cycle Fatigue Cycling at High Temperature for a Type 316LN Stainless Steel: Life-Prediction Techniques and Associated Mechanisms

Science.gov (United States)

Sarkar, Aritra; Nagesha, A.; Parameswaran, P.; Sandhya, R.; Laha, K.; Okazaki, M.

2017-01-01

Cumulative fatigue damage under sequential low cycle fatigue (LCF) and high cycle fatigue (HCF) cycling was investigated at 923 K (650 °C) by conducting HCF tests on specimens subjected to prior LCF cycling at various strain amplitudes. Remnant HCF lives were found to decrease drastically with increase in prior fatigue exposure as a result of strong LCF-HCF interactions. The rate of decrease in remnant lives varied as a function of the applied strain amplitude. A threshold damage in terms of prior LCF life-fraction was found, below which no significant LCF-HCF interaction takes place. Similarly, a critical damage during the LCF pre-cycling marking the highest degree of LCF-HCF interaction was identified which was found to depend on the applied strain amplitude. In view of the non-linear damage accumulation behavior, Miner's linear damage rule proved to be highly non-conservative. Manson's damage curve approach, suitably modified, was found to be a better alternative for predicting the remnant HCF life. The single constant (β) employed in the model, which reflects the damage accumulation of the material under two/multi-level loading conditions is derived from the regression analysis of the experimental results and validated further.

3. Effect of Progressive Muscle Relaxation on the Fatigue and Quality of Life Among Iranian Aging Persons

Directory of Open Access Journals (Sweden)

Ali Hassanpour-Dehkordi

2016-07-01

Full Text Available Since the elderly population is increasing rapidly in developing countries which may decrease the physical activity and exercise and in turn could affect the elderly’s quality of life, this study aimed to investigate the effect of progressive muscle relaxation on the elderly’s quality of life in Iran. In a randomized clinical trial, participants were randomly divided into intervention and control groups. For the intervention group, muscular progressive relaxation was run three days per week for three months (totally 36 sessions. In relaxation, a patient contract a group of his/her muscles in each step and relaxes them after five seconds and finally loosens all muscles and takes five deep breaths. Each session lasts for 45 minutes. The instrument of data gathering consisted of questionnaires on individual’s demographic data and quality of life SF-36. After intervention, quality of life increased significantly in the patients undergoing muscular progressive relaxation and fatigue severity decreased significantly in the intervention group compared to prior to intervention. In addition, there was a statistically significant difference in mean score of physical performance, restricted activity after physical problem, energy, socially function, physical pain, overall hygiene, and quality of life between intervention and control groups. By implementing regular and continuous progressive muscle relaxation, quality of life could be increased in different dimensions in the elderly and the context could be provided to age healthily and enjoy higher health and autonomy. Therefore, all of the therapeutic staffs are recommended to implement this plan to promote the elderly’s quality of life.

4. A case study on relation between roughness, lubrication and fatigue life of rolling bearings

Science.gov (United States)

Balan, M. R.; Tufescu, A.; Cretu, S. S.

2016-08-01

A spherical roller bearing under high radial loading, constant speed and imposed roughness for the contacting surfaces was chosen as case study. Different lubrication regimes were obtained by varying oil viscosity through the operating temperature. For bearings with especially machined contacting surfaces, λ-ratio is firstly determined and its value is used to estimate the particular value of the lubrication parameter κ. Using the λ-ratio approach the paper reveals the relationship between roughness amplitude and the modified rating life of rolling bearings. The roughness values corresponding to good manufacturing practice are possible to be determined for each particular case. Three groups of random Gaussian roughness were generated with the same values for the Ra parameter as used in the modified lives investigations. For medium and especially high radial loads, the contacts between rough surfaces develop, inside the shallow layer, von Mises equivalent stresses higher than the fatigue limit stress. For condition of lack of lubricant or starved lubrication, these findings explain the initiation of the rolling contact fatigue in the shallow layer, close to contacting surfaces.

5. EFFECTS OF MODIFICATION OF THE CARBIDE CHARACTERISTICS THROUGH GRAIN BOUNDARY SERRATION ON CREEP-FATIGUE LIFE IN AUSTENITIC STAINLESS STEELS

Institute of Scientific and Technical Information of China (English)

K．J．Kim; H．U．Hong; K．S．Min; S．W．Nam

2004-01-01

Modification of the carbide characteristics through the grain boundary serration is investigated, using an AISI 316 and 304 stainless steels. In both steels, triangular carbides were observed at straight grain boundaries while planar carbides vere observed at the serrated grain boundaries. The serrated grain boundary energy is observed to be much lower than that of the straight one. Therefore, the carbide morphology is found to be changed from triangular to planar along the serrated boundary to reduce the interfacial energy between the carbide and the matrix. The creep-fatigue properties of these steels at 873K have been investigated. The creep-fatigue life of the sample vith planar carbide at the serrated grain boundary was found to be much longer than that with triangular carbide at the straight one. These results imply that the planar carbides with lower interfacial energy have higher cavitation resistance, resulting in the retardation of cavity nucleation and growth to increase creep-fatigue life.

6. The Effects of Shot and Laser Peening on Fatigue Life and Crack Growth in 2024 Aluminum Alloy and 4340 Steel

Science.gov (United States)

Everett, R. A., Jr.; Matthews, W. T.; Prabhakaran, R.; Newman, J. C., Jr.; Dubberly, M. J.

2001-01-01

Fatigue and crack growth tests have been conducted on 4340 steel and 2024-T3 aluminum alloy, respectively, to assess the effects of shot peening on fatigue life and the effects of shot and laser peening on crack growth. Two current programs involving fixed and rotary-wing aircraft will not be using shot peened structures. Since the shot peening compressive residual stress depth is usually less than the 0.05-inch initial damage tolerance crack size, it is believed by some that shot peening should have no beneficial effects toward retarding crack growth. In this study cracks were initiated from an electronic-discharged machining flaw which was cycled to produce a fatigue crack of approximately 0.05-inches in length and then the specimens were peened. Test results showed that after peening the crack growth rates were noticeably slower when the cracks were fairly short for both the shot and laser peened specimens resulting in a crack growth life that was a factor of 2 to 4 times greater than the results of the average unpeened test. Once the cracks reached a length of approximately 0.1-inches the growth rates were about the same for the peened and unpeened specimens. Fatigue tests on 4340 steel showed that the endurance limit of a test specimen with a 0.002-inch-deep machining-like scratch was reduced by approximately 40 percent. However, if the "scratched" specimen was shot peened after inserting the scratch, the fatigue life returned to almost 100 percent of the unflawed specimens original fatigue life.

7. Surface fatigue life of CBN and vitreous ground carburized and hardened AISI 9310 spur gears

Science.gov (United States)

Townsend, Dennis P.; Patel, P. R.

1988-01-01

Spur gear surface endurance tests were conducted to investigate CBN ground AISI 9310 spur gears for use in aircraft applications, to determine their endurance characteristics and to compare the results with the endurance of standard vitreous ground AISI 9310 spur gears. Tests were conducted with VIM-VAR AISI 9310 carburized and hardened gears that were finish ground with either CBN or vitreous grinding methods. Test conditions were an inlet oil temeprature of 320 K (116 F), an outlet oil temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), and a speed of 10,000 rpm. The CBN ground gears exhibited a surface fatigue life that was slightly better than the vitreous ground gears. The subsurface residual stress of the CBN ground gears was approximately the same as that for the standard vitreous ground gears for the CBN grinding method used.

8. Standard test method for ambient temperature fatigue life of metallic bonded resistance strain gages

CERN Document Server

American Society for Testing and Materials. Philadelphia

2003-01-01

1.1 This test method covers a uniform procedure for the determination of strain gage fatigue life at ambient temperature. A suggested testing equipment design is included. 1.2 This test method does not apply to force transducers or extensometers that use bonded resistance strain gages as sensing elements. 1.3 Strain gages are part of a complex system that includes structure, adhesive, gage, leadwires, instrumentation, and (often) environmental protection. As a result, many things affect the performance of strain gages, including user technique. A further complication is that strain gages, once installed, normally cannot be reinstalled in another location. Therefore, it is not possible to calibrate individual strain gages; performance characteristics are normally presented on a statistical basis. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices ...

9. Impact of restless legs syndrome in patients with inflammatory bowel disease on sleep, fatigue, and quality of life.

Science.gov (United States)

Schindlbeck, Katharina A; Becker, Janek; Berger, Felix; Mehl, Arne; Rewitzer, Charlotte; Geffe, Sarah; Koch, Peter M; Preiß, Jan C; Siegmund, Britta; Maul, Jochen; Marzinzik, Frank

2017-01-01

Inflammatory bowel disease has been associated with neurological symptoms including restless legs syndrome. Here, we investigated the impact of restless legs syndrome in patients with inflammatory bowel disease on sleep, fatigue, mood, cognition, and quality of life. Two groups of inflammatory bowel disease patients, with and without restless legs syndrome, were prospectively evaluated for sleep disorders, fatigue, daytime sleepiness, depression, anxiety, and health-related quality of life. Furthermore, global cognitive function, executive function, attention, and concentration were assessed in both groups. Disease activity and duration of inflammatory bowel disease as well as current medication were assessed by interview. Inflammatory bowel disease patients with and without restless legs syndrome were matched for age, education, severity, and duration of their inflammatory bowel disease. Patients with inflammatory bowel disease and clinically relevant restless leg syndrome suffered significantly more frequent from sleep disturbances including sleep latency and duration, more fatigue, and worse health-related quality of life as compared to inflammatory bowel disease patients without restless legs syndrome. Affect and cognitive function including cognitive flexibility, attention, and concentration showed no significant differences among groups, indicating to be not related to restless legs syndrome. Sleep disorders including longer sleep latency, shorter sleep duration, and fatigue are characteristic symptoms of restless legs syndrome in inflammatory bowel disease patients, resulting in worse health-related quality of life. Therefore, clinicians treating patients with inflammatory bowel disease should be alert for restless legs syndrome.

10. Effects of meditation on anxiety, depression, fatigue, and quality of life of women undergoing radiation therapy for breast cancer.

Science.gov (United States)

Kim, Yeon Hee; Kim, Hwa Jung; Ahn, Seung Do; Seo, Yun Jeong; Kim, So Hee

2013-08-01

To investigate the effects of meditation on anxiety, depression, fatigue, and quality of life in women who are receiving radiation therapy for breast cancer. Randomized, non-program controlled, parallel intervention clinical trial. The ASAN Cancer Center located in Seoul, Korea. The subjects of this study included 102 female breast cancer patients who had undergone breast-conserving surgery; these female patients were randomized into equally assigned meditation control groups, with each group consisting of 51 patients. The test group received a total of 12 meditation therapy sessions during their 6-week radiation therapy period, and the control group underwent only a conventional radiation therapy. The tools used to evaluate the effects of meditation were Hospital Anxiety and Depression scale, Revised Piper Fatigue scale, and European Organization for Research and Treatment of Cancer-Quality of Life Core-30. The results were analyzed based on the principles of intention-to-treat analysis, and, as a corollary analysis, per-protocol analysis was conducted. The breast cancer patients who received meditation therapy compared with the non-intervention group saw improvements in reduction of anxiety (p=.032), fatigue (p=.030), and improvement in global quality of life (p=.028). Based on the results of this study, an affirmation can be made that meditation can be used as a non-invasive intervention treatment for improving fatigue, anxiety, quality of life, and emotional faculties of women with breast cancer. Copyright © 2013 Elsevier Ltd. All rights reserved.

11. Stress and fatigue in sound engineers: the effect of broadcasting in a life show and shift work.

Science.gov (United States)

Vangelova, Katia K

2008-06-01

The aim was to study the time-of-day variations of cortisol, fatigue and sleep disturbances in sound engineers in relation to job task and shift work. The concentration of saliva cortisol and feeling of stress, sleepiness and fatigue were followed at three hour intervals in 21 sound engineers: 13 sound engineers, aged 45.1 +/- 7.3 years, broadcasting in a life show during fast forward rotating shifts and 8 sound engineers, aged 47.1 +/- 9.8 years, making records in a studio during fast rotating day shifts. Cortisol concentration was assessed in saliva with radioimmunological kits. The participants reported for stress symptoms during the shifts and filled sleep diary. The data were analyzed by tests of between-subjects effects (SPSS). A trend for higher cortisol was found with the group broadcasting in a life show. The sound engineers broadcasting in a life show reported higher scores of stress, sleepiness and fatigue, but no significant differences concerning the sleep disturbances between the groups were found. In conclusion our data show moderate level of stress and fatigue with the studied sound engineers, higher with the subjects broadcasting in a life show. The quality of sleep showed no significant differences between the studied groups, an indication that the sound engineers were able to tolerate the fast forward rotating shifts.

12. A Comparative Study on Fatigue Life Optimization of the Intersection between a Longitudinal and a Webframe

DEFF Research Database (Denmark)

Birk-Sørensen, Martin

1996-01-01

The connection between longitudinals and transverse web frames, is a weak point in the fatigue strength of a ship structure. Moreover it is very expensive to repair fatigue damages in these intersections, and a fatigue analysis for a specific detail was therefore carried out in order to seek to i...

13. An influence of static load on fatigue life of parts under combined stress

Directory of Open Access Journals (Sweden)

Svoboda J.

2008-11-01

Full Text Available The paper deals with a special case of multiaxial fatigue in a plain stress possessing one component static and the other dynamic. Exponents of Haigs' limit curves were obtained experimentally both for tensile fatigue test and combined tensile/torgue tests. Errors of estimated fatigue lives are less than 20 %.

14. STRESS-STRAIN FINITE ELEMENT ANALYSIS AND FATIGUE LIFE PREDICTION FOR BOLTED CONNECTIONS

Institute of Scientific and Technical Information of China (English)

2002-01-01

A cyclic plasticity model is used into finite element (FE) method to obtain the details of elastic-plastic stress-strain in the bolts under cyclic axial loading. Two criteria in multiaxial fatigue are employed to predict fatigue lives of bolts. The predicted fatigue lives are in favorable agreement with the experimental results for machined bolts.

15. Fatigue in adolescents and young adults with sickle cell disease: biological and behavioral correlates and health-related quality of life.

Science.gov (United States)

Ameringer, Suzanne; Elswick, R K; Smith, Wally

2014-01-01

This descriptive, correlational study examined fatigue and potential biological and behavioral correlates in adolescents and young adults with sickle cell disease. Sixty adolescents and young adults with sickle cell disease completed the Brief Fatigue Inventory, Multidimensional Fatigue Symptom Inventory-Short Form, Patient Reported Outcomes Measurement Information System (PROMIS) fatigue short form and measures of pain, sleep quality, anxiety, depressive mood, stress, disease severity, and quality of life. Blood samples were obtained for hemoglobin and cytokines. Fatigue scores were mostly moderate in severity. Fatigue interfered to a moderate degree with daily activities and correlated significantly with pain, sleep quality, state and trait anxiety, depressive mood, stress, and quality of life. Fatigue was correlated with hemoglobin on the PROMIS measure. Fatigue was not correlated with cytokines or age, nor differed by disease severity. Fatigue was common in these adolescents and young adults, interfered with daily activities such as school, work and exercise, and significantly correlated with several potentially modifiable factors. As life expectancy increases in sickle cell disease, research is needed to test interventions to reduce fatigue.

16. Comparison of cyclic fatigue life of nickel-titanium files: an examination using high-speed camera

Directory of Open Access Journals (Sweden)

Taha Özyürek

2017-08-01

Full Text Available Objectives To determine the actual revolutions per minute (rpm values and compare the cyclic fatigue life of Reciproc (RPC, VDW GmbH, WaveOne (WO, Dentsply Maillefer, and TF Adaptive (TFA, Axis/SybronEndo nickel-titanium (NiTi file systems using high-speed camera. Materials and Methods Twenty RPC R25 (25/0.08, 20 WO Primary (25/0.08, and 20 TFA ML 1 (25/0.08 files were employed in the present study. The cyclic fatigue tests were performed using a dynamic cyclic fatigue testing device, which has an artificial stainless steel canal with a 60° angle of curvature and a 5-mm radius of curvature. The files were divided into 3 groups (group 1, RPC R25 [RPC]; group 2, WO Primary [WO]; group 3, TF Adaptive ML 1 [TFA]. All the instruments were rotated until fracture during the cyclic fatigue test and slow-motion videos were captured using high-speed camera. The number of cycles to failure (NCF was calculated. The data were analyzed statistically using one-way analysis of variance (ANOVA, p < 0.05. Results The slow-motion videos were indicated that rpm values of the RPC, WO, and TFA groups were 180, 210, and 425, respectively. RPC (3,464.45 ± 487.58 and WO (3,257.63 ± 556.39 groups had significantly longer cyclic fatigue life compared with TFA (1,634.46 ± 300.03 group (p < 0.05. There was no significant difference in the mean length of the fractured fragments. Conclusions Within the limitation of the present study, RPC and WO NiTi files showed significantly longer cyclic fatigue life than TFA NiTi file.

17. Effect of laser shock peening on residual stress and fatigue life of clad 2024 aluminium sheet containing scribe defects

Energy Technology Data Exchange (ETDEWEB)

Dorman, M. [Department of Aerospace Engineering, Cranfield University, Cranfield, Beds, MK43 0AL (United Kingdom); Toparli, M.B. [Materials Engineering, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Smyth, N.; Cini, A. [Department of Materials, Cranfield University, Cranfield, Beds, MK43 0AL (United Kingdom); Fitzpatrick, M.E. [Materials Engineering, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Irving, P.E., E-mail: p.e.irving@cranfield.ac.uk [Department of Materials, Cranfield University, Cranfield, Beds, MK43 0AL (United Kingdom)

2012-06-30

Highlights: Black-Right-Pointing-Pointer Effect of laser peen intensity on local residual stress fields in 2024 aluminium. Black-Right-Pointing-Pointer Peening induces significant changes in surface topography and local hardness. Black-Right-Pointing-Pointer Residual stress at peen spot centre in tension, spot overlap in compression. Black-Right-Pointing-Pointer Notched fatigue lives increased; crack morphology correlated to residual stress field. Black-Right-Pointing-Pointer Large peening power densities can cause fatigue life reduction in notched samples. - Abstract: Laser peening at a range of power densities has been applied to 2 mm-thick sheets of 2024 T351 aluminium. The induced residual stress field was measured using incremental hole drilling and synchrotron X-ray diffraction techniques. Fatigue samples were subjected to identical laser peening treatments followed by scribing at the peen location to introduce stress concentrations, after which they were fatigue tested. The residual stresses were found to be non-biaxial: orthogonal to the peen line they were tensile at the surface, moving into the desired compression with increased depth. Regions of peen spot overlap were associated with large compression strains; the centre of the peen spot remaining tensile. Fatigue lives showed moderate improvement over the life of unpeened samples for 50 {mu}m deep scribes, and slight improvement for samples with 150 {mu}m scribes. Use of the residual stress intensity K{sub resid} approach to calculate fatigue life improvement arising from peening was unsuccessful at predicting the relative effects of the different peening treatments. Possible reasons for this are explored.

18. Effects from fully nonlinear irregular wave forcing on the fatigue life of an offshore wind turbine and its monopile foundation

DEFF Research Database (Denmark)

Schløer, Signe; Bredmose, Henrik; Bingham, Harry B.;

2013-01-01

The effect from fully nonlinear irregular wave forcing on the fatigue life of the foundation and tower of an offshore wind turbine is investigated through aeroelastic calculations. Five representative sea states with increasing significant wave height are considered in a water depth of 40 m....... The waves are both linear and fully nonlinear irregular 2D waves. The wind turbine is the NREL 5-MW reference wind turbine. Fatigue analysis is performed in relation to analysis of the sectional forces in the tower and monopile. Impulsive excitation of the sectional force at the bottom of the tower is seen...

19. Predictions for fatigue crack growth life of cracked pipes and pipe welds using RMS SIF approach and experimental validation

Energy Technology Data Exchange (ETDEWEB)

Arora, Punit, E-mail: punit@barc.gov.in [Bhabha Atomic Research Centre, Department of Atomic Energy, Maharashtra, Mumbai 400 085 (India); Singh, P.K.; Bhasin, Vivek; Vaze, K.K.; Ghosh, A.K. [Bhabha Atomic Research Centre, Department of Atomic Energy, Maharashtra, Mumbai 400 085 (India); Pukazhendhi, D.M.; Gandhi, P.; Raghava, G. [Structural Engineering Research Centre, Chennai 600 113 (India)

2011-10-15

The objective of the present study is to understand the fatigue crack growth behavior in austenitic stainless steel pipes and pipe welds by carrying out analysis/predictions and experiments. The Paris law has been used for the prediction of fatigue crack growth life. To carry out the analysis, Paris constants have been determined for pipe (base) and pipe weld materials by using Compact Tension (CT) specimens machined from the actual pipe/pipe weld. Analyses have been carried out to predict the fatigue crack growth life of the austenitic stainless steel pipes/pipes welds having part through cracks on the outer surface. In the analyses, Stress Intensity Factors (K) have been evaluated through two different schemes. The first scheme considers the 'K' evaluations at two points of the crack front i.e. maximum crack depth and crack tip at the outer surface. The second scheme accounts for the area averaged root mean square stress intensity factor (K{sub RMS}) at deepest and surface points. Crack growth and the crack shape with loading cycles have been evaluated. In order to validate the analytical procedure/results, experiments have been carried out on full scale pipe and pipe welds with part through circumferential crack. Fatigue crack growth life evaluated using both schemes have been compared with experimental results. Use of stress intensity factor (K{sub RMS}) evaluated using second scheme gives better fatigue crack growth life prediction compared to that of first scheme. Fatigue crack growth in pipe weld (Gas Tungsten Arc Welding) can be predicted well using Paris constants of base material but prediction is non-conservative for pipe weld (Shielded Metal Arc Welding). Further, predictions using fatigue crack growth rate curve of ASME produces conservative results for pipe and GTAW pipe welds and comparable results for SMAW pipe welds. - Highlights: > Predicting fatigue crack growth of Austenitic Stainless Steel pipes and pipe welds. > Use of RMS-SIF and

20. Fatigue Life and Microstructure after Multiple Remelting of A359 Matrix Composites Reinforced with SiC Particles

Directory of Open Access Journals (Sweden)

Klasik A.

2016-12-01

Full Text Available The article presents the results of fatigue life tests and microstructure examinations of A359 alloy matrix composites (F3S.10S and F3S.30S containing 10 and 30wt% of SiC particles, subjected to multiple remelting by conventional gravity casting. Mechanical characteristics were determined in a modified low cycle fatigue (MLCF test, enabling rapid estimation of fatigue life and other mechanical parameters in practice of any material. Qualitative and quantitative metallographic examinations were also carried out. The quantitative evaluation of microstructure was performed by computer image analysis. A set of geometrical parameters of the reinforcing particles, pores and eutectic precipitates present in the metal matrix was determined. The relationships between the mechanical parameters, structural characteristics and the number of remelting operations were presented. It was found that up to the fourth remelting, the mechanical characteristics, including fatigue life, are slightly deteriorated but decrease gradually in the subsequent operations of remelting. The observed effect is mainly due to the shrinkage porosity occurring as a result of gravity casting. To eliminate this defect, the use of squeeze casting process was recommended. It has also been shown that multiple remelting can be an easy and economically well-founded alternative to other more expensive recycling methods.

1. Independent effect of fatigue on health-related quality of life in patients with idiopathic Parkinson's disease.

Science.gov (United States)

Dogan, Vasfiye Burcu; Koksal, Ayhan; Dirican, Ayten; Baybas, Sevim; Dirican, Ahmet; Dogan, Gulsum Buse

2015-12-01

Nonmotor symptoms (NMS) of idiopathic Parkinson's disease (IPD), specifically fatigue, depression and sleep disturbances, are important contributors for worse quality of life and poor patient outcomes. The aim of this research is to determine the relationship between fatigue and other NMS and the independent effect of fatigue on health-related quality of life (HRQoL) in patients with IPD. 86 IPD patients and 85 healthy individuals were included in our study. Participants were evaluated by their answers to the Beck Depression Inventory, Fatigue Severity Scale, Epworth Sleepiness Scale and Parkinson's Disease Questionnaire-39. Hoehn-Yahr stage, disease duration, medications and demographical characteristics were also noted. ROC analysis was used to determine the cutoff point for HRQoL. Nonparametric Spearman correlation analysis was used for determining the relationship between variables. Independent factors which affect HRQoL were detected by multiple forward stepwise logistic regression analysis. NMS were associated with each other and with HRQoL when they act concomitantly (p 0.05). The stage of IPD and levodopa-entacapone treatment had independent effects on HRQoL too (p life quality.

2. Synergistic Effects of Frequency and Temperature on Damage Evolution and Life Prediction of Cross-Ply Ceramic Matrix Composites under Tension-Tension Fatigue Loading

Science.gov (United States)

Longbiao, Li

2016-12-01

In this paper, the synergistic effects of loading frequency and testing temperature on the fatigue damage evolution and life prediction of cross-ply SiC/MAS ceramic-matrix composite have been investigated. The damage parameters of the fatigue hysteresis modulus, fatigue hysteresis dissipated energy and the interface shear stress were used to monitor the damage evolution inside of SiC/MAS composite. The evolution of fatigue hysteresis dissipated energy, the interface shear stress and broken fibers fraction versus cycle number, and the fatigue life S-N curves of SiC/MAS composite under the loading frequency of 1 and 10 Hz at 566 °C and 1093 °C in air condition have been predicted. The synergistic effects of the loading frequency and testing temperature on the degradation rate of fatigue hysteresis dissipated energy and the interface shear stress have been analyzed.

3. Review of time-dependent fatigue behavior and life prediction for 2 1/4 Cr-1 Mo steel. [LMFBR

Energy Technology Data Exchange (ETDEWEB)

Booker, M.K.; Majumdar, S.

1982-01-01

Available data on creep-fatigue life and fracture behavior of 2 1/4 Cr-1 Mo steel are reviewed. Whereas creep-fatigue interaction is important for Type 304 stainless steel, oxidation effects appear to dominate the time-dependent fatigue behavior of 2 1/4 Cr-1 Mo steel. Four of the currently available predictive methods - the Linear Damage Rule, Frequency Separation Equation, Strain Range Partitioning Equation, and Damage Rate Equation - are evaluated for their predictive capability. Variations in the parameters for the various predictive methods with temperature, heat of material, heat treatment, and environment are investigated. Relative trends in the lives predicted by the various methods as functions of test duration, waveshape, etc., are discussed. The predictive methods will need modification in order to account for oxidation and aging effects in the 2 1/4 Cr-1 Mo steel. Future tests that will emphasize the difference between the various predictive methods are proposed.

4. An estimation of fatigue life for a carbon fibre/poly ether ether ketone hip joint prosthesis.

Science.gov (United States)

Akay, M; Aslan, N

1995-01-01

A fracture mechanics approach was applied to estimate the life of a prosthesis injection moulded from short carbon fibre reinforced poly ether ether ketone. Flexural modulus and strength, fracture toughness, fatigue endurance limit, fatigue crack growth rate and threshold stress intensity factor were determined. The dimensions of the test pieces were selected to yield fibre orientation and fibre length distributions similar to those obtained in the prosthesis. Stress levels generated in the prosthesis under different activities were estimated by conducting three-dimensional finite element analysis. It was shown by a fracture mechanics approach that a fatigue failure due to the propagation of an embedded elliptical slit, under these stresses, would be unlikely for a crack length smaller than 1.85 mm. However, the cement would fail under the same conditions, irrespective of the type of the prosthesis employed.

5. Finite element analysis of sucker rod couplings with guidelines for improving fatigue life

Energy Technology Data Exchange (ETDEWEB)

Hoffman, E.L. [Sandia National Labs., Albuquerque, NM (United States). Engineering and Structural Mechanics Div.

1997-09-01

The response of a variety of sucker rod couplings to an applied axial load was simulated using axisymmetric finite element models. The calculations investigated three sucker rod sizes and various combinations of the slimhole, Spiralock, and Flexbar modifications to the coupling. In addition, the effect of various make-ups (assembly tightness) on the performance of coupling was investigated. An axial load was applied to the sucker rod ranging from {minus}5 ksi to 40 ksi, encompassing three load cycles identified on a modified Goodman diagram as acceptable for indefinite service life of the sucker rods. The simulations of the various coupling geometries and make-ups were evaluated with respect to how well they accomplish the two primary objectives of preloading threaded couplings: (1) to lock the threaded coupling together so that it will not loosen and eventually uncouple, and (2) to improve the fatigue resistance of the threaded connection by reducing the stress amplitude in the coupling when subjected to cyclic loading. Perhaps the most significant finding in this study was the characterization of the coupling parameters which affect two stress measures. The mean hydrostatic stress, which determines the permissible effective alternating stress, is a function of the coupling make-up. Whereas, the alternating effective stress is a function of the relative stiffnesses of the pin and box sections of the coupling and, as long as the coupling does not separate, is unaffected by the amount of circumferential displacement applied during make-up. The results of this study suggest approaches for improving the fatigue resistance of sucker rod couplings.

6. Estimation of Fatigue Life of Laser Welded AISI304 Stainless Steel T-Joint Based on Experiments and Recommendations in Design Codes

DEFF Research Database (Denmark)

Lambertsen, Søren Heide; Damkilde, Lars; Kristensen, Anders Schmidt;

2013-01-01

In this paper the fatigue behavior of laser welded T-joints of stainless steel AISI304 is investigated experimentally. In the fatigue experiments 36 specimens with a sheet thickness of 1 mm are exposed to one-dimensional cyclic loading. Three different types of specimens are adopted. Three groups....... The non-welded specimens are used to study the influence of heat and surface effects on the fatigue life. The fatigue life from the experiments is compared to fatigue life calculated from the guidelines in the standards DNV-RP-C203 and EUROCODE 3 EN-1993-1-9. Insignificant differences in fatigue life...... of the welded and non-welded specimens are observed in the experiments and the largest difference is found in the High Cycle Fatigue (HCF) area. The specimens show a lower fatigue life compared to DNV-RP-C203 and EUROCODE 3 EN-1993-1-9 when the spe-cimens are exposed to less than 4.0 1E06 cycles. Therefore, we...

7. Life distribution of thermal fatigue crack propagation under random temperature fluctuation with wide-band spectrum

Energy Technology Data Exchange (ETDEWEB)

Toyoda, Michiko; Tanaka, Hiroaki [Kyoto Univ. (Japan)

1995-05-01

Thermal fatigue crack propagation under random temperature fluctuation is theoretically investigated from a probabilistic view point by the use of a Markov approximation method, under the condition that the temporary variation of the inner surface temperature of plate is modeled as a wide-band stationary Gaussian process. First, a crack growth equation is formulated on the basis of the Paris law under the assumption that the stress intensity factor range {Delta}K can be approximated by the local expectation of a relative maximum of the stress intensity factor K. Next it is extended to a random differential equation, where the randomness in crack propagation resistance is taken into account. The Markov approximation method is then applied to derive a residual life distribution function as well as a probability distribution function of the crack length. Finally, numerical examples are shown to examine the quantitative behavior of the residual life distribution, whose results indicate that the present model is applicable even if the spectrum of temperature is of narrow-band type. (author).

8. Interior Fracture Mechanism Analysis and Fatigue Life Prediction of Surface-Hardened Gear Steel under Axial Loading

Directory of Open Access Journals (Sweden)

Wei Li

2016-10-01

Full Text Available The interior defect-induced fracture of surface-hardened metallic materials in the long life region has become a key issue on engineering design. In the present study, the axial loading test with fully reversed condition was performed to examine the fatigue property of a surface-carburized low alloy gear steel in the long life region. Results show that this steel represents the duplex S-N (stress-number of cycles characteristics without conventional fatigue limit related to 107 cycles. Fatigue cracks are all originated from the interior inclusions in the matrix region due to the inhabitation effect of carburized layer. The inclusion induced fracture with fisheye occurs in the short life region below 5 × 105 cycles, whereas the inclusion induced fracture with fine granular area (FGA and fisheye occurs in the long life region beyond 106 cycles. The stress intensity factor range at the front of FGA can be regarded as the threshold value controlling stable growth of interior long crack. The evaluated maximum inclusion size in the effective damage volume of specimen is about 27.29 μm. Considering the size relationships between fisheye and FGA, and inclusion, the developed life prediction method involving crack growth can be acceptable on the basis of the good agreement between the predicted and experimental results.

9. Interior Fracture Mechanism Analysis and Fatigue Life Prediction of Surface-Hardened Gear Steel under Axial Loading.

Science.gov (United States)

Li, Wei; Deng, Hailong; Liu, Pengfei

2016-10-18

The interior defect-induced fracture of surface-hardened metallic materials in the long life region has become a key issue on engineering design. In the present study, the axial loading test with fully reversed condition was performed to examine the fatigue property of a surface-carburized low alloy gear steel in the long life region. Results show that this steel represents the duplex S-N (stress-number of cycles) characteristics without conventional fatigue limit related to 10⁷ cycles. Fatigue cracks are all originated from the interior inclusions in the matrix region due to the inhabitation effect of carburized layer. The inclusion induced fracture with fisheye occurs in the short life region below 5 × 10⁵ cycles, whereas the inclusion induced fracture with fine granular area (FGA) and fisheye occurs in the long life region beyond 10⁶ cycles. The stress intensity factor range at the front of FGA can be regarded as the threshold value controlling stable growth of interior long crack. The evaluated maximum inclusion size in the effective damage volume of specimen is about 27.29 μm. Considering the size relationships between fisheye and FGA, and inclusion, the developed life prediction method involving crack growth can be acceptable on the basis of the good agreement between the predicted and experimental results.

10. Life prediction methodology for thermal-mechanical fatigue and elevated temperature creep design

Science.gov (United States)

Annigeri, Ravindra

Nickel-based superalloys are used for hot section components of gas turbine engines. Life prediction techniques are necessary to assess service damage in superalloy components resulting from thermal-mechanical fatigue (TMF) and elevated temperature creep. A new TMF life model based on continuum damage mechanics has been developed and applied to IN 738 LC substrate material with and without coating. The model also characterizes TMF failure in bulk NiCoCrAlY overlay and NiAl aluminide coatings. The inputs to the TMF life model are mechanical strain range, hold time, peak cycle temperatures and maximum stress measured from the stabilized or mid-life hysteresis loops. A viscoplastic model is used to predict the stress-strain hysteresis loops. A flow rule used in the viscoplastic model characterizes the inelastic strain rate as a function of the applied stress and a set of three internal stress variables known as back stress, drag stress and limit stress. Test results show that the viscoplastic model can reasonably predict time-dependent stress-strain response of the coated material and stress relaxation during hold times. In addition to the TMF life prediction methodology, a model has been developed to characterize the uniaxial and multiaxial creep behavior. An effective stress defined as the applied stress minus the back stress is used to characterize the creep recovery and primary creep behavior. The back stress has terms representing strain hardening, dynamic recovery and thermal recovery. Whenever the back stress is greater than the applied stress, the model predicts a negative creep rate observed during multiple stress and multiple temperature cyclic tests. The model also predicted the rupture time and the remaining life that are important for life assessment. The model has been applied to IN 738 LC, Mar-M247, bulk NiCoCrAlY overlay coating and 316 austenitic stainless steel. The proposed model predicts creep response with a reasonable accuracy for wide range of

11. Improvement of the fatigue life of titanium alloys for biomedical devices through microstructural control.

Science.gov (United States)

Niinomi, Mitsuo; Akahori, Toshikazu

2010-07-01

A limited number of reports exist regarding the systematic investigation or comparison of the fatigue strength of titanium alloys for medical devices, including plain, fretting and notch fatigue, for improvement through various treatments and processes, with respect to related microstructures. This article focuses on the changes and improvements in fatigue strength of newly developed beta-type and practically used alpha + beta-titanium alloys for medical devices through heat treatments, thermomechanical treatments and surface modifications.

12. 悬架下摆臂的疲劳寿命分析%Fatigue Life Analysis of Lower Suspension Arm

Institute of Scientific and Technical Information of China (English)

史建鹏; 管欣

2013-01-01

根据汽车悬架下摆臂所受的极限静载工况下的结构应力分析、道路载荷作用下的疲劳损伤分析和常用行驶工况下的疲劳寿命等分析,采用CAE与台架和道路试验相结合的方法,从多体动力学得到载荷值,应用“惯性释放法”获得不同工况下,下摆臂的应力分布特征；据此确定易出现疲劳损伤的部位,为下摆臂探索出一种一体化疲劳寿命分析方法；采用该方法对某型汽车下摆臂进行分析的结果表明,受到的应力下降1OMPa时,疲劳寿命约能提高1倍.%Based on the analyses on the structural stress of static loads in extreme condition, the fatigue damage under road loads and the fatigue life in normal driving conditions for lower suspension arm and combining CAE technique with road test, the load values are obtained with multi-body dynamics, and by applying inertia relief method the stress distribution features of lower suspension arm are acquired, and based on which the locations are i-dentified where fatigue damages are easy to occur. Thus an integrated fatigue life analysis technique for lower suspension arm is explored, using which the analysis on the lower suspension arm of a real vehicle is conducted with a result showing that for this specific situation a reduction of stress by 10 MPa can lead to nearly a doubling in fatigue life.

13. Mean load effects on the fatigue life of offshore wind turbine monopile foundations

DEFF Research Database (Denmark)

Blasques, José Pedro Albergaria Amaral; Natarajan, Anand

2013-01-01

This paper discusses the importance of mean load effects on the estimation of the fatigue damage in offshore wind turbine monopile foundations. The mud line bending moment time series are generated using a fully coupled aero-hydro-elastic model accounting for non-linear water waves and sea current....... The fatigue damage is analysed in terms of the lifetime fatigue damage equivalent bending moment. Three different mean value correction techniques are considered, namely, Goodman, Walker, and mean sensitivity factor. An increase in the lifetime fatigue damage equivalent bending moment between 6% (mean...

14. Experimental Modeling and Optimization of Fatigue Life and Hardness of Carbon Steel CK35 under Dynamic Buckling

Directory of Open Access Journals (Sweden)

Ahmed Naif Al-Khazraji

2014-12-01

Full Text Available The aim of this paper is to model and optimize the fatigue life and hardness of medium carbon steel CK35 subjected to dynamic buckling. Different ranges of shot peening time (STP and critical points of slenderness ratio which is between the long and intermediate columns, as input factors, were used to obtain their influences on the fatigue life and hardness, as main responses. Experimental measurements of shot peening time and buckling were taken and analyzed using (DESIGN EXPERT 8 experimental design software which was used for modeling and optimization purposes. Mathematical models of responses were obtained and analyzed by ANOVA variance to verify the adequacy of the models. The resultant quadratic models were obtained. A good agreement was found between the results of these models and optimization with the experimental ones with confidence level of 95 %.

15. Lifing the thermo-mechanical fatigue (TMF behaviour of the polycrystalline nickel-based superalloy RR1000

Directory of Open Access Journals (Sweden)

Jones Jonathan

2014-01-01

Full Text Available Microstructural damage and subsequent failures resulting from thermo-mechanical fatigue (TMF loading within the temperature range 300–700 ∘C are investigated for the polycrystalline nickel superalloy, RR1000. Strain controlled TMF experiments were conducted over various mechanical strain ranges, encompassing assorted phase angles, using hollow cylindrical test pieces. The paper explores two scenarios; the first where the mechanical strain range is held constant and comparisons of the fatigue life are made for different phase angle tests, and secondly, the difference between the behaviour of In-phase (IP and − 180 ∘ Out-Of-Phase (OOP tests over a variety of applied strain ranges. It is shown that different lifing approaches are currently required for the two scenarios, with a mean stress based approach being more applicable in the first case, whereas a Basquin-type model proves more appropriate in the second.

16. Perception of fatigue and quality of life in patients with COPD

NARCIS (Netherlands)

Breslin, E; van der Schans, C; Breukink, S; Meek, P; Mercer, K; Volz, W; Louie, S

1998-01-01

Introduction: Although dyspnea is considered the primary activity-limiting symptom in patients with COPD, other symptoms, such as fatigue, are frequently reported, The purpose of this study was to determine the relationship between fatigue and pulmonary function, exercise tolerance, depression, and

17. Estimation of Fatigue-life of Electronic Packages Subjected to Random Vibration Load

Directory of Open Access Journals (Sweden)

M.I. Sakri

2009-01-01

Full Text Available Random vibration is being specified for acceptance tests, screening tests, and qualification tests by manufacturers of electronic equipment meant for military applications, because it has been shown that random vibration more closely represents the true environment in which the electronic equipment must operate. In this paper, the methodology of testing an electronic package subjected to random vibration load is illustrated using Joint Electronic Device Engineering Council’s (JEDEC JESD22-B103B standard. The electronic package mounted at the centre of the printed circuit board was subjected to vibration, variable frequency condition ‘D’ of JEDEC standard for 30 min. After 30 min of random vibration test, the component lead-wires, solderjoints, and PCB were thoroughly inspected for failure. From the observations, it was found that no failure occurred during the test period. The fatigue life of the component, estimated using analytical method, was found to be 96.48 hours.Defence Science Journal, 2009, 59(1, pp.58-62, DOI:http://dx.doi.org/10.14429/dsj.59.1486

18. Demonstrating the Effect of Particle Impact Dampers on the Random Vibration Response and Fatigue Life of Printed Wiring Assemblies

Science.gov (United States)

Knight, Brent; Montgomery, Randall; Geist, David; Hunt, Ron; LaVerde, Bruce; Towner, Robert

2013-01-01

In a recent experimental study, small Particle Impact Dampers (PID) were bonded directly to the surface of printed circuit board (PCB) or printed wiring assemblies (PWA), reducing the random vibration response and increasing the fatigue life. This study provides data verifying practicality of this approach. The measured peak strain and acceleration response of the fundamental out of plane bending mode was significantly attenuated by adding a PID device. Attenuation of this mode is most relevant to the fatigue life of a PWA because the local relative displacements between the board and the supported components, which ultimately cause fatigue failures of the electrical leads of the board-mounted components are dominated by this mode. Applying PID damping at the board-level of assembly provides mitigation with a very small mass impact, especially as compared to isolation at an avionics box or shelf level of assembly. When compared with other mitigation techniques at the PWA level (board thickness, stiffeners, constrained layer damping), a compact PID device has the additional advantage of not needing to be an integral part of the design. A PID can simply be bonded to heritage or commercial off the shelf (COTS) hardware to facilitate its use in environments beyond which it was originally qualified. Finite element analysis and test results show that the beneficial effect is not localized and that the attenuation is not due to the simple addition of mass. No significant, detrimental reduction in frequency was observed. Side-by-side life testing of damped and un-damped boards at two different thicknesses (0.070" and 0.090") has shown that the addition of a PID was much more significant to the fatigue life than increasing the thickness. High speed video, accelerometer, and strain measurements have been collected to correlate with analytical results.

19. Sleep, Fatigue and Quality of Life: A Comparative Analysis among Night Shift Workers with and without Children

Science.gov (United States)

Fernandes-Junior, Silvio Araújo; Ruiz, Francieli Silva; Antonietti, Leandro Stetner; Tufik, Sergio; Túlio de Mello, Marco

2016-01-01

Introduction The reversal of the natural cycle of wakefulness and sleep may cause damage to the health of workers. However, there are few studies evaluating sleep, fatigue and quality of life of night shift workers considering the influence of small children on these variables. Aims Evaluate the sleep time, fatigue and quality of life of night shift workers and verify the relationship between these variables with the presence or absence of children in different age groups. Methods Were evaluated 78 mens shiftworkers, with or without children. Group 1, workers without children (G1-NC), group 2, workers with children pré-school age (G2-PS) and group 3, workers with children school age (G3-S). The sleep time (ST), sleep efficiency (SE), sleep latency (SL) and maximum time awake (MTA) were recorded by actigraphy. The risk of being fatigued at work was estimated by risk index for fatigue (RIF). Results The G1-NC showed a longer ST on working days and when evaluated only the first nights shift, after day off (p<0,005). This sample, the age of the children did not influence the sleep time these workers. The MTA on day off was lower in the workers from G2-PS. The RIF was lower on G1-NC in the first nights shift compared to the other groups. Conclusion In this research, workers without children had higher sleep time during the working days. These workers also were less likely to feel fatigued during night work than workers with children, regardless of age these children. PMID:27391478

20. Cyclic softening as a parameter for prediction of remnant creep rupture life of a Indian reduced activation ferritic–martensitic (IN-RAFM) steel subjected to fatigue exposures

Energy Technology Data Exchange (ETDEWEB)

Sarkar, Aritra, E-mail: aritra@igcar.gov.in [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamil Nadu (India); Vijayanand, V.D.; Shankar, Vani; Parameswaran, P.; Sandhya, R.; Laha, K.; Mathew, M.D.; Jayakumar, T. [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamil Nadu (India); Rajendrakumar, E. [Institute for Plasma Research, Bhat, Gandhinagar, Gujarat (India)

2014-12-15

Sequential fatigue-creep tests were conducted on Indian reduced activation ferritic–martensitic steel at 823 K leading to sharp decrease in residual creep life with increase in prior fatigue exposures. Extensive recovery of martensitic-lath structure taking place during fatigue deformation, manifested as cyclic softening in the cyclic stress response, shortens the residual creep life. Based on the experimental results, cyclic softening occurring during fatigue stage can be correlated with residual creep life, evolving in an empirical model which predicts residual creep life as a function of cyclic softening. Predicted creep lives for specimens pre-cycled at various strain amplitudes are explained on the basis of mechanism of cyclic softening.

1. Comparison of warm laser shock peening and laser shock peening techniques in lengthening the fatigue life of welded joints made of aluminum alloy

Science.gov (United States)

Su, Chun; Zhou, Jianzhong; Meng, Xiankai; Sheng, Jie

2017-07-01

Welded joints made of 6061-T6 Al alloy were studied to evaluate warm laser shock peening (WLSP) and laser shock peening (LSP) processes. The estimation model of laser-induced surface residual stress was examined by means of experiments and numerical analysis. The high-cycle fatigue lives of welded joint specimens treated with WLSP and LSP were estimated by conducting tensile fatigue tests. The fatigue fracture mechanisms of these specimens are studied by surface integrity and fracture surface tests. Experimental results and analysis indicated that the fatigue life of the specimens processed by WLSP was higher than that with LSP. The large increase in fatigue life appeared to be the result of the larger residual stress, more uniform microstructure refinement and the lower surface roughness of the WLSP specimens.

2. Relationship between fatigue life of asphalt concrete and polypropylene/polyester fibers using artificial neural network and genetic algorithm

Institute of Scientific and Technical Information of China (English)

Morteza Vadood; Majid Safar Johari; Ali Reza Rahai

2015-01-01

While various kinds of fibers are used to improve the hot mix asphalt (HMA) performance, a few works have been undertaken on the hybrid fiber-reinforced HMA. Therefore, the fatigue life of modified HMA samples using polypropylene and polyester fibers was evaluated and two models namely regression and artificial neural network (ANN) were used to predict the fatigue life based on the fibers parameters. As ANN contains many parameters such as the number of hidden layers which directly influence the prediction accuracy, genetic algorithm (GA) was used to solve optimization problem for ANN. Moreover, the trial and error method was used to optimize the GA parameters such as the population size. The comparison of the results obtained from regression and optimized ANN with GA shows that the two-hidden-layer ANN with two and five neurons in the first and second hidden layers, respectively, can predict the fatigue life of fiber-reinforced HMA with high accuracy (correlation coefficient of 0.96).

3. A gender-based analysis of work patterns, fatigue, and work/life balance among physicians in postgraduate training.

Science.gov (United States)

Gander, Philippa; Briar, Celia; Garden, Alexander; Purnell, Heather; Woodward, Alistair

2010-09-01

To document fatigue in New Zealand junior doctors in hospital-based clinical training positions and identify work patterns associated with work/life balance difficulties. This workforce has had a duty limitation of 72 hours/week since 1985. The authors chose a gender-based analytical approach because of the increasing proportion of female medical graduates. The authors mailed a confidential questionnaire to all 2,154 eligible junior doctors in 2003. The 1,412 respondents were working > or = 40 hours/week (complete questionnaires from 1,366: response rate: 63%; 49% women). For each participant, the authors calculated a multidimensional fatigue risk score based on sleep and work patterns. Women were more likely to report never/rarely getting enough sleep (P work/life balance and for part-time work, particularly in relation to parenthood. Limitation of duty hours alone is insufficient to manage fatigue risk and difficulties in maintaining work/life balance. These findings have implications for schedule design, professional training, and workforce planning.

4. High-temperature fatigue in metals - A brief review of life prediction methods developed at the Lewis Research Center of NASA

Science.gov (United States)

Halford, G. R.

1983-01-01

The presentation focuses primarily on the progress we at NASA Lewis Research Center have made. The understanding of the phenomenological processes of high temperature fatigue of metals for the purpose of calculating lives of turbine engine hot section components is discussed. Improved understanding resulted in the development of accurate and physically correct life prediction methods such as Strain-Range partitioning for calculating creep fatigue interactions and the Double Linear Damage Rule for predicting potentially severe interactions between high and low cycle fatigue. Examples of other life prediction methods are also discussed. Previously announced in STAR as A83-12159

5. Above-knee prosthesis design based on fatigue life using finite element method and design of experiment.

Science.gov (United States)

Phanphet, Suwattanarwong; Dechjarern, Surangsee; Jomjanyong, Sermkiat

2017-05-01

The main objective of this work is to improve the standard of the existing design of knee prosthesis developed by Thailand's Prostheses Foundation of Her Royal Highness The Princess Mother. The experimental structural tests, based on the ISO 10328, of the existing design showed that a few components failed due to fatigue under normal cyclic loading below the required number of cycles. The finite element (FE) simulations of structural tests on the knee prosthesis were carried out. Fatigue life predictions of knee component materials were modeled based on the Morrow's approach. The fatigue life prediction based on the FE model result was validated with the corresponding structural test and the results agreed well. The new designs of the failed components were studied using the design of experimental approach and finite element analysis of the ISO 10328 structural test of knee prostheses under two separated loading cases. Under ultimate loading, knee prosthesis peak von Mises stress must be less than the yield strength of knee component's material and the total knee deflection must be lower than 2.5mm. The fatigue life prediction of all knee components must be higher than 3,000,000 cycles under normal cyclic loading. The design parameters are the thickness of joint bars, the diameter of lower connector and the thickness of absorber-stopper. The optimized knee prosthesis design meeting all the requirements was recommended. Experimental ISO 10328 structural test of the fabricated knee prosthesis based on the optimized design confirmed the finite element prediction. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

6. Fatigue life prediction and experiment research for composite laminates with circular hole

Institute of Scientific and Technical Information of China (English)

齐红宇; 温卫东; 孙联文

2004-01-01

Based on the fatigue prediction model of exponential function and Whitney-Nuismer(WN) criterion of static strength for the composite material laminate with a circular hole, the stress correct factor (β) was put forward and a new fatigue prediction model for composite material laminate was set up. T300/KH304, which is recently studied and is a high capability composite material, was used as the raw material. In order to gain the factorβ, the fatigue experiments of the laminates with holes in different diameters and the same ratio of width to diameter were conducted. The fatigue analysis and tests of the laminates with a hole 5 mm in diameter are carried out at different stress levels, and the results meet the engineering requirement. The simple, prompt and practical method is provided for the prediction of S-N curve of composite laminate with a circular hole.

7. Study of the Fatigue Life and Weight Optimization of an Automobile Aluminium Alloy Part under Random Road Excitation

Directory of Open Access Journals (Sweden)

A. Saoudi

2010-01-01

Full Text Available Weight optimization of aluminium alloy automobile parts reduces their weight while maintaining their natural frequency away from the frequency range of the power spectral density (PSD that describes the roadway profile. We present our algorithm developed to optimize the weight of an aluminium alloy sample relative to its fatigue life. This new method reduces calculation time; It takes into account the multipoint excitation signal shifted in time, giving a tangle of the constraint signals of the material mesh elements; It also reduces programming costs. We model an aluminium alloy lower vehicle suspension arm under real conditions. The natural frequencies of the part are inversely proportional to the mass and proportional to flexural stiffness, and assumed to be invariable during the process of optimization. The objective function developed in this study is linked directly to the notion of fatigue. The method identifies elements that have less than 10% of the fatigue life of the part's critical element. We achieved a weight loss of 5 to 11% by removing the identified elements following the first iteration.

8. Predicting quality of life in multiple sclerosis: accounting for physical disability, fatigue, cognition, mood disorder, personality, and behavior change.

Science.gov (United States)

Benedict, Ralph H B; Wahlig, Elizabeth; Bakshi, Rohit; Fishman, Inna; Munschauer, Frederick; Zivadinov, Robert; Weinstock-Guttman, Bianca

2005-04-15

Health-related quality of life (HQOL) is poor in multiple sclerosis (MS) but the clinical precipitants of the problem are not well understood. Previous correlative studies demonstrated relationships between various clinical parameters and diminished HQOL in MS. Unfortunately, these studies failed to account for multiple predictors in the same analysis. We endeavored to determine what clinical parameters account for most variance in predicting HQOL, and employability, while accounting for disease course, physical disability, fatigue, cognition, mood disorder, personality, and behavior disorder. In 120 MS patients, we measured HQOL (MS Quality of Life-54) and vocational status (employed vs. disabled) and then conducted detailed clinical testing. Data were analyzed by linear and logistic regression methods. MS patients reported lower HQOL (pPhysical HQOL was predicted by fatigue, depression, and physical disability. Mental HQOL was associated with only depression and fatigue. In contrast, vocational status was predicted by three cognitive tests, conscientiousness, and disease duration (p<0.05). Thus, for the first time, we predicted HQOL in MS while accounting for measures from these many clinical domains. We conclude that self-report HQOL indices are most strongly predicted by measures of depression, whereas vocational status is predicted primarily by objective measures of cognitive function. The findings highlight core clinical problems that merit early identification and further research regarding the development of effective treatment.

9. Energy expenditure in caving.

Science.gov (United States)

Antoni, Giorgia; Marini, Elisabetta; Curreli, Nicoletta; Tuveri, Valerio; Comandini, Ornella; Cabras, Stefano; Gabba, Silvia; Madeddu, Clelia; Crisafulli, Antonio; Rinaldi, Andrea C

2017-01-01

The aim of this study was to determine the energy expenditure of a group of cavers of both genders and different ages and experience during a 10 hour subterranean exploration, using portable metabolimeters. The impact of caving activity on body composition and hydration were also assessed through bioelectrical impedance, and nutritional habits of cavers surveyed. During cave activity, measured total energy expenditure (TEE) was in the range 225-287 kcal/h for women-men (MET = 4.1), respectively; subjects had an energy intake from food in the range 1000-1200 kcal, thus inadequate to restore lost calories. Bayesian statistical analysis estimated the effect of predictive variables on TEE, revealing that experienced subjects had a 5% lower TEE than the less skilled ones and that women required a comparatively larger energy expenditure than men to perform the same task. BIVA (bioelectrical impedance vector analysis) showed that subjects were within the range of normal hydration before and after cave activity, but bioelectrical changes indicated a reduction of extracellular water in men, which might result in hypo-osmolal dehydration in the case of prolonged underground exercise. All these facts should be considered when planning cave explorations, preparing training programs for subjects practising caving, and optimizing a diet for cavers. Further, information gathered through this study could be of value to reduce accidents in caves related to increase in fatigue.

10. Rolling Contact Fatigue Life of Steel Rollers Treated by Cavitation Peening and Shot Peening

Science.gov (United States)

Seki, Masanori; Soyama, Hitoshi; Kobayashi, Yuji; Gowa, Daisuke; Fujii, Masahiro

The purpose of this study is to investigate the influence of peening on the rolling contact fatigue (RCF) life of steel rollers. First, steel rollers were treated by three types of peenings to ensure the same surface roughness of peened rollers. One is the cavitation peening (CP) used a cavitating jet in water with an injection pressure of 30 MPa, and the others are the fine particle peening (FPP) with a shot diameter of 0.1 mm and the normal shot peening (NSP) with a shot diameter of 0.3 mm. The surface hardness and the surface compressive residual stress of the steel rollers were increased by all the peenings. In particular, they were most increased by the FPP. On the other hand, the work-hardened depth due to the CP and the NSP was larger than that due to the FPP. As a result of the RCF tests, the RCF lives of the steel rollers were improved by all the peenings, and they were most improved by the NSP. Judging from the pmax - N curves and the [A(σy/√3 HV)]max - N curves, the improvement in RCF lives due to the FPP depended heavily on the increase in surface hardness due to that, and the effects of the CP and the NSP on the RCF were equivalent under the same surface roughness and the same surface hardness. It follows from these that the surface treatment condition should be selected according to the rolling contact conditions and the failure modes of machine elements.

11. DETERMINATION OF VEHICLE COMPONENTS FATIGUE LIFE BASED ON FEA METHOD AND EXPERIMENTAL ANALYSIS

Directory of Open Access Journals (Sweden)

Arif Senol SENER

2012-01-01

Full Text Available In this study, construction and standardization of a track for performing fatigue and reliability test of light commercial vehicles is described. For the design and process verification of the company’s vehicles one test track is defined. A questionnaire was used to determine the average usage of light commercial vehicles in Turkey. Fatigue characteristics of Turkish roads were determined by analyzing fifty different roads and this article focuses on defining the load spectrum and equivalent fatigue damage of the leaf spring resulting from the accelerated test route. Fatigue analysis and estimated lifespan of the part were calculated using Finite Element Analyses and verified by the Palmgren-Miner rule. When the customer profile is taken into consideration; Turkish customer automotive usage profile, the aim of usage of this kind of vehicle (LCV, fatigue characteristics of Turkish roads for this vehicle were determined and around Bursa one accelerated test tracks were formed for the reliability and fatigue test for the related company, linear analysis executed on the FEA of the spring was more convenient were obtained.

12. Bending resistance and dynamic and static cyclic fatigue life of Reciproc and WaveOne large instruments.

Science.gov (United States)

De-Deus, Gustavo; Leal Vieira, Victor Talarico; Nogueira da Silva, Emmanuel João; Lopes, Helio; Elias, Carlos Nelson; Moreira, Edson Jorge

2014-04-01

The aim of the present study was to evaluate the bending resistance and the dynamic and static cyclic fatigue life of Reciproc R40 and WaveOne large instruments. A sample of 68 nickel-titanium instruments (25 mm in length) for use under reciprocation movement (Reciproc and WaveOne) from 3 different lots was tested. Reciproc R40 and WaveOne Large files, both of which had a nominal size of 0.40 mm at D0, were selected. The bending resistance was performed in 10 instruments of each system by using a universal testing machine. Dynamic and static models for cyclic fatigue testing were performed by using a custom-made device. For these tests, an artificial canal measuring 1.4 mm in diameter and 19 mm total length was fabricated from a stainless steel tube. Scanning electron microscopy analysis was performed to determine the mode of fracture. Statistical analysis was performed by using parametric methods, 1-way analysis of variance. Post hoc pair-wise comparisons were performed by using Tukey test for multiple comparisons. WaveOne instruments presented significantly higher bending resistance than Reciproc (P < .05). Moreover, Reciproc revealed a significantly longer cyclic fatigue life (P < .05) in both static and dynamic tests (P < .05). Reciproc R40 instruments resisted dynamic and static cyclic fatigue significantly more than WaveOne Large instruments. Furthermore, WaveOne instruments presented significantly less flexibility than Reciproc. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

13. Comparison of Fatigue Life Between C/SiC and SiC/SiC Ceramic-Matrix Composites at Room and Elevated Temperatures

Science.gov (United States)

Longbiao, Li

2016-10-01

In this paper, the comparison of fatigue life between C/SiC and SiC/SiC ceramic-matrix composites (CMCs) at room and elevated temperatures has been investigated. An effective coefficient of the fiber volume fraction along the loading direction (ECFL) was introduced to describe the fiber architecture of preforms. Under cyclic fatigue loading, the fibers broken fraction was determined by combining the interface wear model and fibers statistical failure model at room temperature, and interface/fibers oxidation model, interface wear model and fibers statistical failure model at elevated temperatures in the oxidative environments. When the broken fibers fraction approaches to the critical value, the composites fatigue fracture. The fatigue life S-N curves and fatigue limits of cross-ply, 2D and 3D C/SiC and SiC/SiC composites at room temperature, 550 °C in air, 750 °C in dry and humid condition, 800 °C in air, 1000 °C in argon and air, 1100 °C, 1300 °C and 1500 °C in vacuum, have been predicted. At room temperature, the fatigue limit of 2D C/SiC composite with ECFL of 20 % lies between 0.78 and 0.8 tensile strength; and the fatigue limit of 2D SiC/SiC composite with ECFL of 20 % lies between 0.75 and 0.85 tensile strength. The fatigue limit of 2D C/SiC composite increases to 0.83 tensile strength with ECFL increasing from 20 to 22.5 %, and the fatigue limit of 3D C/SiC composite is 0.85 tensile strength with ECFL of 37 %. The fatigue performance of 2D SiC/SiC composite is better than that of 2D C/SiC composite at elevated temperatures in oxidative environment.

14. Disease-free ovarian cancer patients report severe pain and fatigue over time: prospective quality of life assessment in a consecutive series.

Science.gov (United States)

Shinde, S; Wanger, T; Novotny, P; Grudem, M; Jatoi, A

2015-01-01

objective: Among ovarian cancer patients, cancer treatment is aggressive and yet survival is often so limited; hence, this study sought to measure quality of life with the ultimate goal of identifying ways of improving it over the duration of these patients' lives. The medical records of all ovarian cancer patients who received some/all of their initial chemotherapy at the Mayo Clinic in Rochester, Minnesota from late 2010 through 2012 were reviewed. Patient-reported quality of life was derived from the following ten-point linear analogue scale questions which had been administered to all patients: 1) How would you describe your degree of pain, on average? 2) How would you describe your level of fatigue, on average? 3) How would you describe your overall quality of life? Quality of life data were censored upon cancer recurrence. Among 59 eligible patients, the median cumulative interval during which quality of life was serially assessed was 1.15 years (range: three months, 3.2 years). Area under the curve for pain, fatigue, and global quality of life showed no statistically significant differences between patients treated with dose-dense chemotherapy with carboplatin/paclitaxel (n = 10) versus three-week chemotherapy with carboplatin/paclitaxel (n = 36) versus other (n = 13). Although pain, fatigue, and global quality of life improved over time, 35 of 59 (59%) patients reported grade 4 or worse pain during follow up, and 47 of 59 (80%) reported grade 4 or worse fatigue (higher scores denote worse pain or fatigue). After completion of cancer treatment, 30 (51%) described grade 4 or worse pain or fatigue. The most common pain site was the abdomen/pelvis, followed by the back, followed by the hands, feet, fingers, and toes. In ovarian cancer patients who remain cancer-free, severe pain and fatigue occur years after cancer treatment. Further research should focus on how best to address these symptoms.

15. Optimal Fatigue Testing

DEFF Research Database (Denmark)

Faber, M. H.; Sørensen, John Dalsgaard; Kroon, I. B.

1993-01-01

This paper considers the reassessment of the reliability of tubular joints subjected to fatigue load. The reassessment is considered in two parts namely the task of utilizing new experimental data on fatigue life to update the reliability of the tubular joint ant the task of planning new fatigue ...

16. Prediction of low-cycle fatigue-life by acoustic emission—1: 2024-T3 aluminum alloy, and —2: 7075-T6 aluminum alloy

Energy Technology Data Exchange (ETDEWEB)

Baram, J. [Ben-Gurion Univ. of the Negev, Beer Sheva (Israel). Materials Engineering Division; Rosen, M. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials and Molecular Research Division

1981-01-01

1: In this paper, low-cycle fatigue tests were conducted by tension-tension until rupture, on a 2024-T3 aluminum alloy sheet. Initial crack sizes and orientations in the fatigue specimens were found to be randomly distributed. Acoustic emission was continuously monitored during the tests. Every few hundred cycles, the acoustic signal having the highest peak-amplitude, was recorded as an extremal event for the elapsed period. This high peak-amplitude is related to a fast crack propagation rate through a phenomenological relationship. The extremal peak amplitudes are shown by an ordered statistics treatment, to be extremally distributed. The statistical treatment enables the prediction of the number of cycles left until failure. Predictions performed a posteriori based on results gained early in each fatigue test are in good agreement with actual fatigue lives. Finally, the amplitude distribution analysis of the acoustic signals emitted during cyclic stress appears to be a promising nondestructive method of predicting fatigue life. 2: In this paper, low cycle high stress fatigue tests were conducted by tension-tension on an Alclad 7075-T6 aluminum sheet alloy, until rupture. Initial crack sizes and orientations in the fatigue specimens were randomly distributed. Acoustic emission was continuously monitored during the tests. Extremal peak-amplitudes, equivalent to extremal crack-propagation rates, are shown to be extremally Weibull distributed. The prediction of the number of cycles left until failure is made possible, using an ordered statistics treatment and an experimental equipment parameter obtained in previous experiments (Part 1). The predicted life-times are in good agreement with the actual fatigue lives. Finally, the amplitude distribution analysis of the acoustic signals emitted during cyclic stress has been proven to be a feasible nondestructive method of predicting fatigue life.

17. Associations of Midlife to Late Life Fatigue With Physical Performance and Strength in Early Old Age

DEFF Research Database (Denmark)

Mänty, Minna Regina; Kuh, Diana; Cooper, Rachel

2015-01-01

objective measures: grip strength, standing balance, chair rising, and timed get-up-and-go (TUG) tests. RESULTS: There were associations between reports of frequent fatigue at both ages and poorer grip strength, chair rise, and TUG performance at 60 to 64 years. Furthermore, individuals reporting frequent...... fatigue at both ages had weaker grip strength (β = -4.09 kg, 95% confidence interval [CI] = -6.71 to -1.48) and slower chair rise (β = -4.65 repetitions/min, 95% CI = -6.65 to -2.64) and TUG (β = -4.22 cm/s, 95% CI = -12.16 to -2.28) speeds when compared with those who reported no fatigue at both time...

18. Fatigue in Rheumatoid Arthritis.

Science.gov (United States)

Katz, Patricia

2017-05-01

The purpose of this study was to review the current information on fatigue in rheumatoid arthritis (RA). Severe fatigue is common among individuals with RA and has a significant impact on quality of life (QOL). RA-related factors (e.g., inflammation, pain) are associated with greater fatigue, but other factors, such as obesity, physical inactivity, sleep disturbance, and depression, explain the majority of variation in fatigue. Medications targeting RA have little effect on fatigue. Instead, the most effective interventions seem to address non-RA-specific factors such as physical inactivity or use cognitive behavioral approaches. No recommendations have been made for tools to measure fatigue in RA, leading to potential difficulty comparing studies. Although fatigue has great impact on patients' QOL, effective interventions that are feasible for broad dissemination remain elusive. Additional multi-faceted research is needed to identify modifiable sources of fatigue. Such research would be enhanced by harmonization of fatigue measurement across studies.

19. Synergistic Effects of Temperature, Oxidation and Multicracking Modes on Damage Evolution and Life Prediction of 2D Woven Ceramic-Matrix Composites under Tension-Tension Fatigue Loading

Science.gov (United States)

Longbiao, Li

2017-08-01

In this paper, the synergistic effects of temperature, oxidation and multicracking modes on damage evolution and life prediction in 2D woven ceramic-matrix composites (CMCs) have been investigated. The damage parameter of fatigue hysteresis dissipated energy and the interface shear stress were used to monitor the damage evolution inside of CMCs. Under cyclic fatigue loading, the fibers broken fraction was determined by combining the interface/fiber oxidation model, interface wear model and fibers statistical failure model at elevated temperature, based on the assumption that the fiber strength is subjected to two-parameter Weibull distribution and the load carried by broken and intact fibers satisfy the Global Load Sharing (GLS) criterion. When the broken fibers fraction approaches to the critical value, the composite fatigue fractures. The evolution of fatigue hysteresis dissipated energy, the interface shear stress and broken fibers fraction versus cycle number, and the fatigue life S-N curves of SiC/SiC at 1000, 1200 and 1300 °C in air and steam condition have been predicted. The synergistic effects of temperature, oxidation, fatigue peak stress, and multicracking modes on the evolution of interface shear stress and fatigue hysteresis dissipated energy versus cycle numbers curves have been analyzed.

20. Fatigue Life Prediction of Fiber-Reinforced Ceramic-Matrix Composites with Different Fiber Preforms at Room and Elevated Temperatures

Directory of Open Access Journals (Sweden)

Longbiao Li

2016-03-01

Full Text Available In this paper, the fatigue life of fiber-reinforced ceramic-matrix composites (CMCs with different fiber preforms, i.e., unidirectional, cross-ply, 2D (two dimensional, 2.5D and 3D CMCs at room and elevated temperatures in air and oxidative environments, has been predicted using the micromechanics approach. An effective coefficient of the fiber volume fraction along the loading direction (ECFL was introduced to describe the fiber architecture of preforms. The statistical matrix multicracking model and fracture mechanics interface debonding criterion were used to determine the matrix crack spacing and interface debonded length. Under cyclic fatigue loading, the fiber broken fraction was determined by combining the interface wear model and fiber statistical failure model at room temperature, and interface/fiber oxidation model, interface wear model and fiber statistical failure model at elevated temperatures, based on the assumption that the fiber strength is subjected to two-parameter Weibull distribution and the load carried by broken and intact fibers satisfies the Global Load Sharing (GLS criterion. When the broken fiber fraction approaches the critical value, the composites fatigue fracture.

1. Fatigue life prediction in a unidirectional glass-epoxy composite material subjected to off-axis cyclic loads

Directory of Open Access Journals (Sweden)

Revuelta, D.

2005-03-01

Full Text Available Most of today s fatigue analysis and design methods for composite laminates were developed primarily on the basis of experience with homogeneous metals. Such methods are subject to serious drawbacks, however, because the failure the modes of failure observed in metals. A theoretical model for predicting the fatigue life of continuous glass-fibre/epoxy composite materials under general loading conditions has been developed on the basis of fundamental fatigue failure modes and local failure criteria.

La mayoría de los actuales métodos de cálculo y diseño a fatiga de estructuras de materiales compuestos se han desarrollado principalmente a partir de la experiencia previa en materiales metálicos homogéneos. Sin embargo, estos métodos presentan serios inconvenientes debido a que la heterogeneidad y micro estructura orientada características de los materiales compuestos laminados provocan modos de fallo diferentes a los de los metales. Basándose en los modos fundamentales de rotura por fatiga y en criterios de rotura local, se desarrolla un modelo teórico de vida a fatiga para materiales compuestos de matriz epoxi reforzados con fibra de vidrio bajo condiciones generales de carga

2. [Effects of Lifestyle Intervention on Fatigue, Nutritional Status and Quality of Life in Patients with Gynecologic Cancer].

Science.gov (United States)

An, Hyunjin; Nho, Ju Hee; Yoo, Sunyoung; Kim, Hyunmin; Nho, Minji; Yoo, Hojeong

2015-12-01

The purpose of this study was to examine the effect of lifestyle intervention on the development of fatigue, nutritional status and quality of life of patients with gynecologic cancer. A nonequivalent control group quasi-experimental design was used. Participants were 49 patients with gynecologic cancer. They were assigned to the experiment group (n=24) or the control group (n=25). The lifestyle intervention for this study consisted of physical activity, nutritional education, telephone call counseling, health counseling, monitoring for lifestyle, and affective support based on Cox's Interaction Model of Client Health Behavior and was implemented for six weeks. Significant group differences were found for fatigue (p =.037), nutritional status (p =.034) and social/family well-being (p =.035) in these patients with gynecologic cancer. Results indicate that this lifestyle intervention is effective in lessening fatigue, and improving nutritional status and social/family well-being. Therefore, nurses in hospitals should develop strategies to expand and provide lifestyle interventions for patients with cancer.

3. FATIGUE LIFE PREDICTION BASED ON MACROSCOPIC PLASTIC ZONE ON FRACTURE SURFACE OF AISI-SAE 1018 STEEL

Directory of Open Access Journals (Sweden)

G.M. Domínguez Almaraz

2010-06-01

Full Text Available This paper deals with rotating bending fatigue tests at high speed (150 Hz carried out on AISI-SAE 1018 steel with a high content of impurities (non metallic inclusions, for which the high experimental stress inside the specimen is close to the elastic limit of the material. Simulations of rotating loading are obtained by Visual NASTRAN software in order to determine the numerical stresse and strain distributions inside a hypothetical homogeneous specimen; later, this information is used for the experimental set up. A general description of experimental test machine and experimental conditions are developed and then, the experimental results are presented and discussed according the observed failure origin related to the non metallic inclusions and the associated high stress zones. Finally, a simple model is proposed to predict the fatigue life for this non homogeneous steel under high speed rotating bending fatigue tests close to the elastic limit, based on the rate between the visual macro-plastic deformation zone at fracture surface and the total fracture surface, together with the crack initiation inclusion (or inclusions located at this zone.

4. Effect of Application of Short and Long Holds on Fatigue Life of Modified 9Cr-1Mo Steel Weld Joint

Science.gov (United States)

Shankar, Vani; Mariappan, K.; Sandhya, R.; Mathew, M. D.; Jayakumar, T.

2013-11-01

Modified 9Cr-1Mo steel is a heat-treatable steel and hence the microstructure is temperature sensitive. During welding, the weld joint (WJ) is exposed to various temperatures resulting in a complex heterogeneous microstructure across the weld joint, such as the weld metal, heat-affected zone (HAZ) (consisting of coarse-grained HAZ, fine-grained HAZ, and intercritical HAZ), and the unaffected base metal of varying mechanical properties. The overall creep-fatigue interaction (CFI) response of the WJ is hence due to a complex interplay between various factors such as surface oxides and stress relaxation (SR) occurring in each microstructural zone. It has been demonstrated that SR occurring during application of hold in a CFI cycle is an important parameter that controls fatigue life. Creep-fatigue damage in a cavitation-resistant material such as modified 9Cr-1Mo steel base metal is accommodated in the form of microstructural degradation. However, due to the complex heterogeneous microstructure across the weld joint, SR will be different in different microstructural zones. Hence, the damage is accommodated in the form of preferential coarsening of the substructure, cavity formation around the coarsened carbides, and new surface formation such as cracks in the soft heat-affected zone.

5. Fatigue life analysis of cracked gas receiver of emergency cut-off system in gas gathering station

Science.gov (United States)

Hu, Junzhi; Zhou, Jiyong; Li, Siyuan

2017-06-01

Small-scale air compressor and gas receiver are used as the driving gas of the emergency cut-off system in gas gathering station. Operation of block valve is ensured by starting and stopping compressor automatically. The frequent start-stop of compressor and the pressure fluctuation pose a threat to the service life of gas receiver, and then affect normal operation of the emergency cut-off system and security of gas gathering station. In this paper, the fatigue life of a pressure vessel with axial semi-elliptical surface crack in the inner wall is analyzed under the varying pressure by means of the theory of fracture mechanics. The influences of the amplitude of pressure fluctuation and the initial crack size on the residual life of gas receiver are discussed. It provides a basis for setting the working parameters of gas receiver of emergency cut-off system and determining the maintenance cycle.

6. Effect of Fe ion concentration on fatigue life of carbon steel in aqueous CO2 environment

DEFF Research Database (Denmark)

Rogowska, Magdalena; Gudme, J.; Rubin, A.

2016-01-01

In this work, the corrosion fatigue behaviour of steel armours used in the flexible pipes, in aqueous solutions initially containing different concentrations of Fe2+, was investigated by four-point bending testing under saturated 1 bar CO2 condition. Corrosion fatigue results were supported with ex...... of Fe2+ marginally above the solubility limit of FeCO3 compared to the samples tested in highly supersaturated solution of Fe2+. Results revealed that the impact of the alternating stresses on the corrosion behaviour of samples reduces with lowering the applied stresses. At the stress range of 100 MPa...

7. Estimation method for random sonic fatigue life of thin-walled structure of a combustor liner based on stress probability distribution%Estimation method for random sonic fatigue life of thin-walled structure of a combustor liner based on stress probability distribution

Institute of Scientific and Technical Information of China (English)

SHA Yun-dong; GUO Xiao-peng; LIAO Lian-fang; XIE Li-juan

2011-01-01

As to the sonic fatigue problem of an aero-engine combustor liner structure under the random acoustic loadings, an effective method for predicting the fatigue life of a structure under random loadings was studied. Firstly, the probability distribution of Von Mises stress of thin-walled structure under random loadings was studied, analysis suggested that probability density function of Von Mises stress process accord approximately with two-parameter Weibull distribution. The formula for calculating Weibull parameters were given. Based on the Miner linear theory, the method for predicting the random sonic fatigue life based on the stress probability density was developed, and the model for fatigue life prediction was constructed. As an example, an aero-engine combustor liner structure was considered. The power spectrum density (PSD) of the vibrational stress response was calculated by using the coupled FEM/BEM (finite element method/boundary element method) model, the fatigue life was estimated by using the constructed model. And considering the influence of the wide frequency band, the calculated results were modified. Comparetive analysis shows that the estimated results of sonic fatigue of the combustor liner structure by using Weibull distribution of Von Mises stress are more conservative than using Dirlik distribution to some extend. The results show that the methods presented in this paper are practical for the random fatigue life analysis of the aeronautical thin-walled structures.

8. Effect of load ratio and saltwater corrosive environment on the initiation life of fatigue of 10Ni5CrMoV steel

Science.gov (United States)

Xie, Xing; Yi, Hong; Xu, Jian; Gen, Liming; Chen, Luyun

2017-09-01

Fatigue initiation life has been studied with 10CrNi5MoV steel for use in ocean engineering at different load ratios and in different environmental media. The microstructure and micro-topography have been observed and analyzed by means of SEM, EDS and EBSD. Our findings indicate that, the initiation life of 10Ni5CrMoV steel in seawater is shorter than that in air, and the difference in longevity is larger with the increasing of load ratio. Corrosion pits had a great influence on initial corrosion fatigue life.

9. Fatigue strain-life behavior of carbon and low-alloy steels, austenitic stainless steels, and Alloy 600 in LWR environments

Energy Technology Data Exchange (ETDEWEB)

Keisler, J.; Chopra, O.K.; Shack, W.J. [Argonne National Lab., IL (United States)

1995-08-01

The existing fatigue strain vs. life (S-N) data, foreign and domestic, for carbon and low-alloy steels, austenitic stainless steels, and Alloy 600 used in the construction of nuclear power plant components have been compiled and categorized according to material, loading, and environmental conditions. Statistical models have been developed for estimating the effects of the various service conditions on the fatigue life of these materials. The results of a rigorous statistical analysis have been used to estimate the probability of initiating a fatigue crack. Data in the literature were reviewed to evaluate the effects of size, geometry, and surface finish of a component on its fatigue life. The fatigue S-N curves for components have been determined by adjusting the probability distribution curves for smooth test specimens for the effect of mean stress and applying design margins to account for the uncertainties due to component size/geometry and surface finish. The significance of the effect of environment on the current Code design curve and on the proposed interim design curves published in NUREG/CR-5999 is discussed. Estimations of the probability of fatigue cracking in sample components from BWRs and PWRs are presented.

10. The effect of music and progressive muscle relaxation on anxiety, fatigue, and quality of life in family caregivers of hospice patients.

Science.gov (United States)

Choi, Yoon Kyung

2010-01-01

The purpose of this study was to examine the effects of music, progressive muscle relaxation (PMR), and music combined with progressive muscle relaxation on the reduction of anxiety, fatigue, and improvement of quality of life in family hospice caregivers. Subjects (N = 32) were divided randomly into 4 groups: control, music only, progressive muscle relaxation only, and music combined with progressive muscle relaxation and were tested twice a week for a duration of 2 weeks. A pre and posttest measuring anxiety and fatigue was administered each session. Quality of life was measured only on the first and last session. Results of three-way mixed design ANOVA indicated no significant main effect for group. However, results revealed a significant main effect for pretest and posttest on anxiety F(1, 28) = 51.82, p fatigue, F(1, 28) = 32.86, p fatigue F(3, 84) = 5.21, p fatigue (r(32) = .55, p fatigue and quality of life (r(32) = -.53, p < .01).

11. A New Paradigm of Fatigue Variability Behavior and Implications for Life Prediction (Preprint)

Science.gov (United States)

2006-06-01

31] S. Suresh, Fatigue of Materials, Cambridge University Press, 1991. [32] A. S. Beranger, X. Feaugas, and M. Clavel , Mater. Sci. Eng., Vol...A172, p. 31, 1993. [33] X. Feaugas and M. Clavel , Acta Materialia, Vol. 45, p. 2685, 1997. [34] D. L. McDowell, K. Gall, M. F. Horstememyer, and J. Fan

12. Sleep, fatigue, depression, and quality of life in survivors of childhood acute lymphoblastic leukemia.

NARCIS (Netherlands)

Gordijn, M.S.; Litsenburg, R.R. van; Gemke, R.J.; Huisman, J.; Bierings, M.B.; Hoogerbrugge, P.M.; Kaspers, G.J.L.

2013-01-01

BACKGROUND: With the improved survival of childhood acute lymphoblastic leukemia (ALL), the effect of treatment on psychosocial well-being becomes increasingly relevant. Literature on sleep and fatigue during treatment is emerging. However, information on these subjects after treatment is sparse. Th

13. Sleep, fatigue, depression, and quality of life in survivors of childhood acute lymphoblastic leukemia.

NARCIS (Netherlands)

Gordijn, M.S.; Litsenburg, R.R. van; Gemke, R.J.; Huisman, J.; Bierings, M.B.; Hoogerbrugge, P.M.; Kaspers, G.J.L.

2013-01-01

BACKGROUND: With the improved survival of childhood acute lymphoblastic leukemia (ALL), the effect of treatment on psychosocial well-being becomes increasingly relevant. Literature on sleep and fatigue during treatment is emerging. However, information on these subjects after treatment is sparse.

14. Sleep, fatigue, depression, and quality of life in survivors of childhood acute lymphoblastic leukemia.

NARCIS (Netherlands)

Gordijn, M.S.; Litsenburg, R.R. van; Gemke, R.J.; Huisman, J.; Bierings, M.B.; Hoogerbrugge, P.M.; Kaspers, G.J.L.

2013-01-01

BACKGROUND: With the improved survival of childhood acute lymphoblastic leukemia (ALL), the effect of treatment on psychosocial well-being becomes increasingly relevant. Literature on sleep and fatigue during treatment is emerging. However, information on these subjects after treatment is sparse. Th

15. Further Investigations to Improve the Fatigue Life of the Mirage IIID Wing Main Spar.

Science.gov (United States)

1985-01-01

Airworthiness Division Canberra, Mr. C. Torkington Statutory & State Authorities and Industry Trans-Australia Airlines, Library Qantas Airways Limited ...t No limitations 13. b CQiti toi ath pu rp ot( cin,’ annaarwIr; mwy be twMwcf U’~TtI?’ ciedjoJ a tot 13 14 .onW 16. COSATI Group 2 Fatigue (materials

16. Research on the Fatigue Property of HFW Pipe Welded Seam and Fatigue Life Forecast Method%HFW钢管焊缝疲劳特性与疲劳寿命预测方法研究

Institute of Scientific and Technical Information of China (English)

韩军; 高惠临; 韩新利

2011-01-01

受停输启用和供需变动的影响,油气管道的输送压力会发生周期性的变化,疲劳失效问题异常突出.特别是对于含有裂纹缺陷的管道,在疲劳载荷的作用下,若管道的应力强度因子幅超过疲劳裂纹扩展门槛值,裂纹就会发生疲劳扩展.当裂纹扩展到一定程度,超过管道运行压力下所能承受的临界缺陷极限尺寸,管道就会发生疲劳失效,从而影响到管道的使用寿命.采用高频疲劳试验机测试了X80钢级HFW焊管焊缝的疲劳裂纹扩展门槛值与疲劳裂纹扩展速率,结合API 579《适用性评价规范》中推荐的失效评估图技术(FAD)和Miner线性疲劳损伤积累理论,考虑了多种应力比对管道疲劳寿命的影响,建立了双参数HFW管道的疲劳寿命预测方法.%The transportation pressure of oil and gas pipeline can change periodically because of restart and supply change, so the fatigue failure problems stand out exceptionally. Especially for pipeline with crack defect, when the value of stress intensity factor exceeds fatigue crack expansion threshold value under fatigue load, the crack will expand; when crack expansion exceed critical defect extreme dimension under pipeline operation pressure, the fatigue failure of pipeline will happen, this will affect useful life of pipeline. In this article, the fatigue crack expansion threshold value of X80 HFW pipe welded seam and fatigue crack propagation rate were tested by using high-frequency fatigue testing machine, combined with the failure assessment diagram (FAD) recommended in API 579 Fitness-for-service Specification and the Miner's linear cumulative damage theory, considering the effect of combined stress ratio on pipeline fatigue life, the fatigue life forecast method for two-parameter HFW pipeline was established.

17. The Effect of Group Mindfulness-based Stress Reduction and Consciousness Yoga Program on Quality of Life and Fatigue Severity in Patients with MS

Directory of Open Access Journals (Sweden)

Somayeh Nejati

2016-12-01

Full Text Available Introduction: The chronic nature of Multiple Sclerosis (MS, have can leave devastating effects on quality of life and fatigue. The present research aimed to study the effect of group Mindfulness-based Stress Reduction (MBSR and conscious yoga program on the quality of life and fatigue severity among patients with MS. Methods: This study was quasi-experimental with intervention and control groups. The statistical population included all members to MS Society of Tehran Province, 24 of whom diagnosed with MS were selected as the sample based on the inclusion criteria. The subjects were randomly assigned into the test group (12 patients and the control group (12 patients. MS Quality of Life-54 (MSQOL-54 and Fatigue Severity Scale (FSS were used for data collection. Subjects in the test group underwent a MBSR and conscious yoga program in 8 two-hour sessions. The data were analyzed using the SPSS ver.13 software. Results: The study findings showed that there was a significant difference between subjects in the experimental and control groups in terms of mean score of some subscales of quality of life including physical health, role limitations due to physical and emotional problems, energy, emotional well-being, health distress, health perception, and satisfaction with sexual function, overall quality of life, and fatigue severity. Conclusion: The results show that the program is effective in reduction of fatigue severity and improving some subscales of quality of life in MS patients. Hence, this supportive method can be used as an effective way for improving quality of life and relieving fatigue in MS patients.

18. The Effect of Group Mindfulness-based Stress Reduction and Consciousness Yoga Program on Quality of Life and Fatigue Severity in Patients with MS.

Science.gov (United States)

Nejati, Somayeh; Rajezi Esfahani, Sepideh; Rahmani, Soheila; Afrookhteh, Gita; Hoveida, Shahrzad

2016-12-01

Introduction: The chronic nature of Multiple Sclerosis (MS), have can leave devastating effects on quality of life and fatigue. The present research aimed to study the effect of group Mindfulness-based Stress Reduction (MBSR) and conscious yoga program on the quality of life and fatigue severity among patients with MS. Methods: This study was quasi-experimental with intervention and control groups. The statistical population included all members to MS Society of Tehran Province, 24 of whom diagnosed with MS were selected as the sample based on the inclusion criteria. The subjects were randomly assigned into the test group (12 patients) and the control group (12 patients). MS Quality of Life-54 (MSQOL-54) and Fatigue Severity Scale (FSS) were used for data collection. Subjects in the test group underwent a MBSR and conscious yoga program in 8 two-hour sessions. The data were analyzed using the SPSS ver.13 software. Results: The study findings showed that there was a significant difference between subjects in the experimental and control groups in terms of mean score of some subscales of quality of life including physical health, role limitations due to physical and emotional problems, energy, emotional well-being, health distress, health perception, and satisfaction with sexual function, overall quality of life, and fatigue severity. Conclusion: The results show that the program is effective in reduction of fatigue severity and improving some subscales of quality of life in MS patients. Hence, this supportive method can be used as an effective way for improving quality of life and relieving fatigue in MS patients.

19. The Effect of Group Mindfulness-based Stress Reduction and Consciousness Yoga Program on Quality of Life and Fatigue Severity in Patients with MS

Science.gov (United States)

Nejati, Somayeh; Rajezi Esfahani, Sepideh; Rahmani, Soheila; Afrookhteh, Gita; Hoveida, Shahrzad

2016-01-01

Introduction: The chronic nature of Multiple Sclerosis (MS), have can leave devastating effects on quality of life and fatigue. The present research aimed to study the effect of group Mindfulness-based Stress Reduction (MBSR) and conscious yoga program on the quality of life and fatigue severity among patients with MS. Methods: This study was quasi-experimental with intervention and control groups. The statistical population included all members to MS Society of Tehran Province, 24 of whom diagnosed with MS were selected as the sample based on the inclusion criteria. The subjects were randomly assigned into the test group (12 patients) and the control group (12 patients). MS Quality of Life-54 (MSQOL-54) and Fatigue Severity Scale (FSS) were used for data collection. Subjects in the test group underwent a MBSR and conscious yoga program in 8 two-hour sessions. The data were analyzed using the SPSS ver.13 software. Results: The study findings showed that there was a significant difference between subjects in the experimental and control groups in terms of mean score of some subscales of quality of life including physical health, role limitations due to physical and emotional problems, energy, emotional well-being, health distress, health perception, and satisfaction with sexual function, overall quality of life, and fatigue severity. Conclusion: The results show that the program is effective in reduction of fatigue severity and improving some subscales of quality of life in MS patients. Hence, this supportive method can be used as an effective way for improving quality of life and relieving fatigue in MS patients. PMID:28032077

20. Perceived Quality of Work Life and Risk for Compassion Fatigue Among Oncology Nurses: A Mixed-Methods Study.

Science.gov (United States)

Denigris, Jami; Fisher, Kathleen; Maley, MaryKay; Nolan, Elizabeth

2016-05-01

To examine factors that influenced the nurse's perceived quality of work life and risk for compassion fatigue (CF). The specific aims of the study were to describe the (a) relationship among nurse characteristics and perceived quality of work life, (b) relationship between personal life stress and perceived quality of work life, and (c) the nurse's beliefs about his or her risk for CF. . A descriptive, mixed-methods study. . A hematology-oncology unit in a large urban teaching hospital in Pennsylvania. . 20 oncology nurses.  . Descriptive study using questionnaires and in-depth interviews. The variables were nurse characteristics, personal life stress, and quality of work life. Data were analyzed descriptively and thematically. Scores on the self-report questionnaires were compared to themes. . Personal life stressors, measured by combining the Impact of Events Scale and Life Events Scale, identified powerful or severe impacts on well-being for 30% of nurse respondents in this study, theoretically placing them at risk for CF. However, qualitative data did not complement the results of the Life Events Scale, and 55% of the nurses described their overall work experiences as "life-affirming and rewarding." The participants provided multiple sources of their work-related stress, including subcategories of communication breakdown, work environment/institution, and care-driven factors.  . Overall, oncology nurses experienced positive reinforcement at work and they had little concern about individual or organizational effectiveness. Positive experiences offset the negative and balanced out the risk for CF. . The identification of personal and social contributors, as well as solutions to work-related stress, supports the philosophical premises (i.e., conceptual model) that the circumstances that place a nurse at risk for CF are socially constructed. Nurses can achieve greater empathy through self-understanding and translate this learning to patient care.

1. Stress Analysis and Fatigue Analysis of Front Axle of Heavy-Duty Truck using ANSYS Ncode Design Life for Different Loading Cases

Directory of Open Access Journals (Sweden)

Hemant L. Aghav

2016-06-01

Full Text Available Front axle of heavy duty truck is the important component of vehicle and needs good design under the various loading conditions of the complete vehicle. Aim of the project is to stress analysis and predict the life of front axle for vertical, and vertical and braking loading case. The fatigue life of front axle is generally estimated by stress life approach and strain life approach method. Front axle beam assembly was modeled in the NX cad software. Meshing and Stress analysis is performed by ANSYS workbench and fatigue analysis is performed by NCODE design life ANSYS tool under different loading cases. Fatigue life of axle obtained by FEA method is more than 2 x 105 cycles, which is considered as safe for vertical loading case. Similarly, Fatigue life of axle obtained is more than 4 x 103 cycles, which is considered as safe for vertical and braking loading case. The max stress region is below spring pad of axle for vertical loading and in the goose neck of axle for vertical and braking loading case

2. Reliability analysis for aeroengine turbine disc fatigue life with multiple random variables based on distributed collaborative response surface method

Institute of Scientific and Technical Information of China (English)

高海峰; 白广忱; 高阳; 鲍天未

2015-01-01

The fatigue life of aeroengine turbine disc presents great dispersion due to the randomness of the basic variables, such as applied load, working temperature, geometrical dimensions and material properties. In order to ameliorate reliability analysis efficiency without loss of reliability, the distributed collaborative response surface method (DCRSM) was proposed, and its basic theories were established in this work. Considering the failure dependency among the failure modes, the distributed response surface was constructed to establish the relationship between the failure mode and the relevant random variables. Then, the failure modes were considered as the random variables of system response to obtain the distributed collaborative response surface model based on structure failure criterion. Finally, the given turbine disc structure was employed to illustrate the feasibility and validity of the presented method. Through the comparison of DCRSM, Monte Carlo method (MCM) and the traditional response surface method (RSM), the results show that the computational precision for DCRSM is more consistent with MCM than RSM, while DCRSM needs far less computing time than MCM and RSM under the same simulation conditions. Thus, DCRSM is demonstrated to be a feasible and valid approach for improving the computational efficiency of reliability analysis for aeroengine turbine disc fatigue life with multiple random variables, and has great potential value for the complicated mechanical structure with multi-component and multi-failure mode.

3. [Health care expenditures and the aging population].

Science.gov (United States)

Felder, S

2012-05-01

The impact of a longer life on future health care expenditures will be quite moderate because of the high costs of dying and the compression of mortality in old age. If not age per se but proximity to death determines the bulk of expenditures, a shift in the mortality risk to higher ages will not significantly affect lifetime health care expenditures, as death occurs only once in every life. A calculation of the demographic effect on health care expenditures in Germany up until 2050 that explicitly accounts for costs in the last years of life leads to a significantly lower demographic impact on per-capita expenditures than a calculation based on crude age-specific health expenditures.

4. Indentation hardness: A simple test that correlates with the dissipated-energy predictor for fatigue-life in bovine pericardium membranes for bioprosthetic heart valves.

Science.gov (United States)

Tobaruela, Almudena; Rojo, Francisco Javier; García Paez, José María; Bourges, Jean Yves; Herrero, Eduardo Jorge; Millán, Isabel; Alvarez, Lourdes; Cordon, Ángeles; Guinea, Gustavo V

2016-08-01

The aim of this study was to evaluate the variation of hardness with fatigue in calf pericardium, a biomaterial commonly used in bioprosthetic heart valves, and its relationship with the energy dissipated during the first fatigue cycle that has been shown to be a predictor of fatigue-life (García Páez et al., 2006, 2007; Rojo et al., 2010). Fatigue tests were performed in vitro on 24 pericardium specimens cut in a root-to-apex direction. The specimens were subjected to a maximum stress of 1MPa in blocks of 10, 25, 50, 100, 250, 500, 1000 and 1500 cycles. By means of a modified Shore A hardness test procedure, the hardness of the specimen was measured before and after fatigue tests. Results showed a significant correlation of such hardness with fatigue performance and with the energy dissipated in the first cycle of fatigue, a predictor of pericardium durability. The study showed indentation hardness as a simple and reliable indicator of mechanical performance, one which could be easily implemented in improving tissue selection.

5. A Study on the Effects on Low Cycle Fatigue Life of a High Pressure Turbine Nozzle due to the Perturbation of Crystal Orientation of Grain of DS Materials

Energy Technology Data Exchange (ETDEWEB)

Huh, Jae Sung; Kang, Young Seok; Rhee, Dong Ho [Korea Aerospace Research Institute, Daejeon (Korea, Republic of)

2016-07-15

High pressure components of a gas turbine engine are generally made of nickel-base superalloys, using precision casting process due to complicated geometries with intricate channels and cooling holes. Turbine components manufactured from directionally solidified and single crystal materials have columnar grains; however, it is found that the crystals do not grow in its preferred direction, although the orientation can be controlled. This anisotropy can lead to the variations of elastic and Hill's parameters in constitutive equations, and they alter stress distributions and the low cycle fatigue life. We aims to evaluate the effects of perturbed crystal orientations on the structural integrity of a directionally solidified nozzle using low cycle fatigue life. We also attempt to show the necessity for the control of allowed manufacturing errors and stochastic analysis. Our approaches included conjugate heat transfer and structural analysis, along with low cycle fatigue life assessment.

6. Multimodal intervention improves fatigue and quality of life in subjects with progressive multiple sclerosis: a pilot study

Directory of Open Access Journals (Sweden)

Bisht B

2015-02-01

Full Text Available Babita Bisht,1 Warren G Darling,2 E Torage Shivapour,3 Susan K Lutgendorf,4–6 Linda G Snetselaar,7 Catherine A Chenard,1 Terry L Wahls1,8 1Department of Internal Medicine, Carver College of Medicine, University of Iowa, 2Department of Health and Human Physiology, College of Liberal Arts and Sciences, University of Iowa, 3Department of Neurology, Carver College of Medicine, University of Iowa, 4Department of Psychology, College of Liberal Arts and Sciences, University of Iowa, 5Department of Obstetrics and Gynecology, Carver College of Medicine, University of Iowa, 6Department of Urology, Carver College of Medicine, University of Iowa, 7Department of Epidemiology, College of Public Health, University of Iowa, 8Department of Internal Medicine, VA Medical Center, Iowa City, IA, USA Background: Fatigue is a disabling symptom of multiple sclerosis (MS and reduces quality of life. The aim of this study was to investigate the effects of a multimodal intervention, including a modified Paleolithic diet, nutritional supplements, stretching, strengthening exercises with electrical stimulation of trunk and lower limb muscles, and stress management on perceived fatigue and quality of life of persons with progressive MS. Methods: Twenty subjects with progressive MS and average Expanded Disability Status Scale (EDSS score of 6.2 (range: 3.5–8.0 participated in the 12-month phase of the study. Assessments were completed at baseline and at 3 months, 6 months, 9 months, and 12 months. Safety analyses were based on monthly side effects questionnaires and blood analyses at 1 month, 3 months, 6 months, 9 months, and 12 months. Results: Subjects showed good adherence (assessed from subjects' daily logs with this intervention and did not report any serious side effects. Fatigue Severity Scale (FSS and Performance Scales-fatigue subscale scores decreased in 12 months (P<0.0005. Average FSS scores of eleven subjects showed clinically significant reduction (more than

7. Effect of interaction of embedded crack and free surface on remaining fatigue life

Directory of Open Access Journals (Sweden)

Genshichiro Katsumata

2016-12-01

Full Text Available Embedded crack located near free surface of a component interacts with the free surface. When the distance between the free surface and the embedded crack is short, stress at the crack tip ligament is higher than that at the other area of the cracked section. It can be easily expected that fatigue crack growth is fast, when the embedded crack locates near the free surface. To avoid catastrophic failures caused by fast fatigue crack growth at the crack tip ligament, fitness-for-service (FFS codes provide crack-to-surface proximity rules. The proximity rules are used to determine whether the cracks should be treated as embedded cracks as-is, or transformed to surface cracks. Although the concepts of the proximity rules are the same, the specific criteria and the rules to transform embedded cracks into surface cracks differ amongst FFS codes. This paper focuses on the interaction between an embedded crack and a free surface of a component as well as on its effects on the remaining fatigue lives of embedded cracks using the proximity rules provided by the FFS codes. It is shown that the remaining fatigue lives for the embedded cracks strongly depend on the crack aspect ratio and location from the component free surface. In addition, it can be said that the proximity criteria defined by the API and RSE-M codes give overly conservative remaining lives. On the contrary, the WES and AME codes always give long remaining lives and non-conservative estimations. When the crack aspect ratio is small, ASME code gives non-conservative estimation.

8. The Influence of Secondary Bending on Fatigue Life Improvement in Bolted Joints

Science.gov (United States)

1993-08-01

Canberra) ASTA Engineering, Document Control Office Ansett Airlines of Australia, Library Qantas Airways Limit»! . Hawker de Havilland Aast Pty Ltd...320 MPa. The four non-bending specimens were tested at a net-area stress level of 350 MPa only. SPATE (Stress Pattern Analysis by measurement of...Lives A two-way analysis of variance of the fatigue data from the secondary-bending specimens (Table 4) indicated that cold expansion provides a

9. Factors affecting the corrosion fatigue life in nickel based superalloys for disc applications

OpenAIRE

Rosier Hollie; Perkins Karen; Girling Andrew; Leggett Jonathan; Gibson Grant

2014-01-01

The nickel based superalloy 720Li is employed in the gas turbine due to its mechanical performance at elevated temperature. A comprehensive assessment of the materials behaviour under representative service conditions is reported to address the drive for ever increasing temperatures and more arduous environmental exposure. Fatigue experiments have been performed in an air and air/SOx environment at 700 ∘C containing a mixed salt as a contaminant. There is an intimate relationship between loca...

10. The Effect of Residual Stress State in the Notch Root Region Caused by the Hold Period of the Overload to the Fatigue Life

OpenAIRE

Anindito Purnowidodo; Ari Wahyudi; Rudy Soenoko; Khairul Anam

2015-01-01

In the present study, the effect of the overload together with the hold period of the overload to the fatigue life associating with the crack emerging from the notch root region is investigated because the region is vulnerable to the plastic deformation. The result of the study shows that the fatigue life is affected by the residual stress state in front of the notch root, and the state of the residual stress depends on the constant amplitude load condition following of the overload. The resi...

11. A Predictive Framework for Thermomechanical Fatigue Life of High Silicon Molybdenum Ductile Cast Iron Based on Considerations of Strain Energy Dissipation

Science.gov (United States)

Avery, Katherine R.

Isothermal low cycle fatigue (LCF) and anisothermal thermomechanical fatigue (TMF) tests were conducted on a high silicon molybdenum (HiSiMo) cast iron for temperatures up to 1073K. LCF and out-of-phase (OP) TMF lives were significantly reduced when the temperature was near 673K due to an embrittlement phenomenon which decreases the ductility of HiSiMo at this temperature. In this case, intergranular fracture was predominant, and magnesium was observed at the fracture surface. When the thermal cycle did not include 673K, the failure mode was predominantly transgranular, and magnesium was not present on the fracture surface. The in-phase (IP) TMF lives were unaffected when the thermal cycle included 673K, and the predominant failure mode was found to be transgranular fracture, regardless of the temperature. No magnesium was present on the IP TMF fracture surfaces. Thus, the embrittlement phenomenon was found to contribute to fatigue damage only when the temperature was near 673K and a tensile stress was present. To account for the temperature- and stress-dependence of the embrittlement phenomenon on the TMF life of HiSiMo cast iron, an original model based on the cyclic inelastic energy dissipation is proposed which accounts for temperature-dependent differences in the rate of fatigue damage accumulation in tension and compression. The proposed model has few empirical parameters. Despite the simplicity of the model, the predicted fatigue life shows good agreement with more than 130 uniaxial low cycle and thermomechanical fatigue tests, cyclic creep tests, and tests conducted at slow strain rates and with hold times. The proposed model was implemented in a multiaxial formulation and applied to the fatigue life prediction of an exhaust manifold subjected to severe thermal cycles. The simulation results show good agreement with the failure locations and number of cycles to failure observed in a component-level experiment.

12. Quantifying the contribution of changes in healthcare expenditures and smoking to the reversal of the trend in life expectancy in the Netherlands Health policies, systems and management in high-income countries

NARCIS (Netherlands)

F. Peters (Frederick); W.J. Nusselder (Wilma); Reibling, N. (Nadine); Wegner-Siegmundt, C. (Christian); J.P. Mackenbach (Johan)

2015-01-01

textabstractBackground: Since 2001 the Netherlands has shown a sharp upturn in life expectancy (LE) after a longer period of slower improvement. This study assessed whether changes in healthcare expenditure (HCE) explain this reversal in trends in LE. As an alternative explanation, the impact of cha

13. Consequences of variations in spatial turbulence characteristics for fatigue life time of wind turbines

Energy Technology Data Exchange (ETDEWEB)

Larsen, G.C.

1998-09-01

The fatigue loading of turbines situated in complex terrain is investigated in order to determine the crucial parameters in the spatial structure of the turbulence in such situations. The parameter study is performed by means of numerical calculations, and it embraces three different wind turbine types, representing a pitch controlled concept, a stall controlled concept, and a stall controlled concept with an extremely flexible tower. For each of the turbine concepts, the fatigue load sensibility to the selected turbulence characteristics are investigated for three different mean wind speeds at hub height. The selected mean wind speeds represent the linear-, the stall-, and the post stall aerodynamic region for the stall controlled turbines and analogously the unregulated-, the partly regulated-, and the fully regulated regime for the pitch controlled turbine. Denoting the turbulence component in the mean wind direction by u, the lateral turbulence component by v, and the vertical turbulence component by w, the selected turbulence characteristics comprise the u-turbulence length scale, the ratio between the v- and w-turbulence intensities and the u-turbulence intensity, the uu-coherence decay factor, and finally the u-v and u-w cross-correlations. The turbulence length scale in the mean wind direction gives rise to significant modification of the fatigue loading on all the investigated wind turbine concepts, but for the other selected parameter variations, large individual differences exists between the turbines. With respect to sensitivity to the performed parameter variations, the Vestas V39 wind turbine is the most robust of the investigated turbines. The Nordtank 500/37 turbine, equipped with the (artificial) soft tower, is by far the most sensitive of the investigated turbine concepts - also much more sensitive than the conventional Nordtank 500/37 turbine equipped with a traditional tower. (au) 2 tabs., 43 ills., 7 refs.

14. The effect of group mindfulness - based stress reduction program and conscious yoga on the fatigue severity and global and specific life quality in women with breast cancer.

Science.gov (United States)

Rahmani, Soheila; Talepasand, Siavash

2015-01-01

Cancer is not merely an event with a certain end, but it is a permanent and vague situation that is determined by delayed effects due to the disease, its treatment and its related psychological issues. The aim of this study was to examine the effectiveness of the mindfulness-based stress reduction program and conscious yoga on the mental fatigue severity and life quality of women with breast cancer. This was a quasi-experimental study with a pre-test, post-test and control group. In this study, 24 patients with the diagnosis of breast cancer were selected among the patients who referred to the Division of Oncology and Radiotherapy of Imam Hossein hospital in Tehran using available sampling method, and were randomly assigned into the experimental and control groups. All the participants completed the Fatigue Severity Scale, Global Life Quality of Cancer Patient and Specific Life Quality of Cancer Patient questionnaires. Data were analyzed by multivariate repeated measurement variance analysis model. Findings revealed that the mindfulness-based stress reduction treatment significantly improved the overall quality of life, role, cognitive, emotion, social functions and pain and fatigue symptoms in global life quality in the experimental group. It also significantly improved the body image, future functions and therapy side effects in specific life quality of the experimental group compared to the control group. In addition, fatigue severity caused by cancer was reduced significantly. The results showed that the mindfulness - based stress reduction treatment can be effective in improving global and specific life quality and fatigue severity in women with breast cancer.

15. Fatigue Performance and Fatigue Life Prediction of Aluminum Resistance Spot Welded Tensile Shear Specimen%铝合金点焊拉剪接头疲劳性能及寿命分析

Institute of Scientific and Technical Information of China (English)

石燕栋; 郭海丁

2014-01-01

Fatigue performance of spot welds of aluminum alloy AA5754 was investigated experi-mentally herein .Fatigue failure mode of spot welded tensile shear specimen was discussed and fatigue crack growth path was also explored .Theoretical crack growth angle was determined for tensile shear specimen ,which was under mix mode I/II loading ,and results were verified by measured angles of failed specimens .Local stress intensity factor at nugget circumference was derived ,modified by actual fatigue crack length in sheet thickness and treated as a fatigue parameter K(i) in fatigue data correla-tion .The proposed fatigue delete parameter is proven efficient in correlating fatigue data and can be used for fatigue life prediction of aluminum resistance spot welds .%研究了铝合金A A 5754点焊拉剪接头的疲劳性能，获得了不同厚度试件的载荷寿命曲线。研究了铝合金焊点的疲劳失效模式，讨论了焊点疲劳裂纹的扩展形式，并测量了裂纹扩展路径与点焊熔核界面之间的角度。分析了点焊拉剪试件在同时承受I型和II型载荷时，疲劳裂纹的扩展方向，并与测量值进行了比较。利用疲劳破坏后沿铝板厚度方向的实际裂纹长度修正了裂纹尖端的局部应力强度因子，提出了评价焊点寿命的疲劳参量 K （i），并对试验数据进行了分析比较。结果证明 K （i）可以有效关联试件尺寸效应和焊点疲劳寿命，能够用于预测焊点疲劳寿命。

16. Motor, psychiatric and fatigue features associated with nutritional status and its effects on quality of life in Parkinson's disease patients.

Directory of Open Access Journals (Sweden)

Full Text Available OBJECTIVES: Parkinson's disease (PD patients are more likely to develop impaired nutritional status because of the symptoms, medications and complications of the disease. However, little is known about the determinants and consequences of malnutrition in PD. This study aimed to investigate the association of motor, psychiatric and fatigue features with nutritional status as well as the effects of malnutrition on different aspects of quality of life (QoL in PD patients. METHODS: One hundred and fifty patients with idiopathic PD (IPD were recruited in this study. A demographic checklist, the Unified Parkinson's Disease Rating Scale (UPDRS, the Hospital Anxiety and Depression Scale (HADS and the Fatigue Severity Scale (FSS were completed through face-to-face interviews and clinical examinations. The health-related QoL (HRQoL was also evaluated by means of the Parkinson's Disease Questionnaire (PDQ-39. For evaluation of nutritional status, the Mini Nutritional Assessment (MNA questionnaire was applied together with anthropometric measurements. RESULTS: Thirty seven (25.3% patients were at risk of malnutrition and another 3 (2.1% were malnourished. The total score of the UPDRS scale (r =  -0.613, P<0.001 and PD duration (r =  -0.284, P = 0.002 had a significant inverse correlation with the total MNA score. The median score of the Hoehn and Yahr stage was significantly higher in PD patients with abnormal nutritional status [2.5 vs. 2.0; P<0.001]. More severe anxiety [8.8 vs. 5.9; P = 0.002], depression [9.0 vs. 3.6; P<0.001] and fatigue [5.4 vs. 4.2; P<0.001] were observed in PD patients with abnormal nutritional status. Except for stigma, all other domains of the PDQ-39 were significantly correlated with the total score of the MNA. CONCLUSION: Our study demonstrates that disease duration, severity of motor and psychiatric symptoms (depression, anxiety and fatigue are associated with nutritional status in PD. Different aspects of the HRQoL were

17. A critical review of fracture mechanics as a tool for multiaxial fatigue life prediction of plastics1

Directory of Open Access Journals (Sweden)

Anders Winkler

2015-07-01

of crack initiation, as well as the use of fracture mechanics for multiaxial fatigue life prediction of injectionmoulded plastics. Numerical tools have been utilised alongside experimental experience and public domain data to offer what we hope will be a contemporary overview, and offer an outlook for future research into the matter

18. TiNi-based films for elastocaloric microcooling— Fatigue life and device performance

Science.gov (United States)

Ossmer, H.; Chluba, C.; Kauffmann-Weiss, S.; Quandt, E.; Kohl, M.

2016-06-01

The global trend of miniaturization and concomitant increase of functionality in microelectronics, microoptics, and various other fields in microtechnology leads to an emerging demand for temperature control at small scales. In this realm, elastocaloric cooling is an interesting alternative to thermoelectrics due to the large latent heat and good down-scaling behavior. Here, we investigate the elastocaloric effect due to a stress-induced phase transformation in binary TiNi and quaternary TiNiCuCo films of 20 μm thickness produced by DC magnetron sputtering. The mesoscale mechanical and thermal performance, as well as the fatigue behavior are studied by uniaxial tensile tests combined with infrared thermography and digital image correlation measurements. Binary films exhibit strong features of fatigue, involving a transition from Lüders-like to homogeneous transformation behavior within three superelastic cycles. Quaternary films, in contrast, show stable Lüders-like transformation without any signs of degradation. The elastocaloric temperature change under adiabatic conditions is -15 K and -12 K for TiNi and TiNiCuCo films, respectively. First-of-its-kind heat pump demonstrators are developed that make use of out-of-plane deflection of film bridges. Owing to their large surface-to-volume ratio, the demonstrators reveal rapid heat transfer. The TiNiCuCo-based devices, for instance, generate a temperature difference of 3.5 K within 13 s. The coefficients of performance of the demonstrators are about 3.

19. Development of a life time assessment method for power plant components subjected to complex multiaxial fatigue loadings; Entwicklung einer Methode zur Lebensdauerbewertung von Kraftwerkskomponenten bei komplexer mehrachsiger Schwingbeanspruchung

Energy Technology Data Exchange (ETDEWEB)

Fesich, Thomas M. [Stuttgart Univ. (Germany). Inst. fuer Materialpruefung, Werkstoffkunde und Festigkeitslehre

2012-11-01

Technical components are loaded by forces and moments that can be constant or dynamic. Therefore multi-axial loadings can develop dependent on load and/or geometry of the component. The evaluation of multi-axial loadings is still not solved, mainly because the time dependent stresses can cause in complex loading states. Since in contrary to static failures no significant changes of material characteristics are observable in case of fatigue failures a sufficiently accurate lifetime assessment is of main importance. In nuclear engineering the components are mostly individual constructions that need the demonstration of fatigue resistance in the frame of a local fatigue analysis. For the materials side the Woehler curve is sufficient since representative component test would not be economic. The national standards include guidelines for the determination of reference values for complex fatigue loadings that are very conservative or only applicable for definite tasks. The presented of an advanced integrated multi-axial fatigue life concept is an experimentally verified technique that allows a realistic evaluation of the multi-axial loading of components and lifetime assessment based on the so called fatigue damage parameter.

20. Interval Solution for Nonlinear Programming of Maximizing the Fatigue Life of V-Belt under Polymorphic Uncertain Environment

Directory of Open Access Journals (Sweden)

Zhong Wan

2013-01-01

Full Text Available In accord with the practical engineering design conditions, a nonlinear programming model is constructed for maximizing the fatigue life of V-belt drive in which some polymorphic uncertainties are incorporated. For a given satisfaction level and a confidence level, an equivalent formulation of this uncertain optimization model is obtained where only interval parameters are involved. Based on the concepts of maximal and minimal range inequalities for describing interval inequality, the interval parameter model is decomposed into two standard nonlinear programming problems, and an algorithm, called two-step based sampling algorithm, is developed to find an interval optimal solution for the original problem. Case study is employed to demonstrate the validity and practicability of the constructed model and the algorithm.

1. National Health Expenditure Data

Data.gov (United States)

U.S. Department of Health & Human Services — National Health Expenditure Accounts are comprised of the following, National Health Expenditures - Historical and Projected, Age Estimates, State Health...

2. Pain in People with Multiple Sclerosis: Associations with Modifiable Lifestyle Factors, Fatigue, Depression, Anxiety, and Mental Health Quality of Life

Directory of Open Access Journals (Sweden)

Claudia H. Marck

2017-09-01

Full Text Available BackgroundPeople with multiple sclerosis (MS often experience pain, which can interfere with mobility, employment, and quality of life (QOL.MethodsThis cross-sectional study explored associations between pain, demographic, disease, and modifiable lifestyle factors in an international sample of people with MS recruited online.ResultsSubstantial pain, of moderate/severe intensity and interfering at least moderately with work/household or enjoyment of life in the past 4 weeks, was reported by 682/2,362 (28.9%. Substantial pain was associated with fatigue (odds ratio (OR: 6.7, 95% confidence interval (CI: 4.9,9.3, depression (OR:4.0, 95% CI:3.2,5.1, anxiety (OR:2.4, 95% CI:1.9,2.9, and lower mental health QOL (Mean Difference: −14.7, 95% CI:−16.6,−12.8. Regression analyses showed that smoking (OR: 2.0, 95% CI:1.35,2.87 and obesity (OR:2.1, 95% CI: 1.5,2.8, moderate alcohol use (OR: 0.7, 95% CI:0.5,0.9, moderate (OR 0.7, 95% CI: 0.55,0.98 or high (OR 0.6, 95% CI: 0.4,0.8 physical activity level, and healthy diet (OR 0.8, 95% CI: 0.75,0.95, per 10 points were associated with substantial pain.ConclusionOur results show clear associations with modifiable lifestyle factors and substantial pain in MS. These factors are already considered in the prevention and management of pain in other populations but have not previously been considered in MS. Conversely, pain and associated common MS comorbidities, such as depression, anxiety, and fatigue, may hamper efforts to start or maintain healthy behaviors. Strategies to overcome these barriers need to be considered. Further research should clarify the direction of these associations.

3. Associations between nausea, vomiting, fatigue and health-related quality of life of women in early pregnancy: The generation r study

NARCIS (Netherlands)

G. Bai (Guannan); I.J. Korfage (Ida); E.H.D. Hafkamp-De Groen (Esther); V.W.V. Jaddoe (Vincent); Mautner, E. (Eva); H. Raat (Hein)

2016-01-01

textabstractThe objective of this study was to evaluate the independent associations between nausea, vomiting, fatigue and health-related quality of life of women in early pregnancy in the Generation R study, which is a prospective mother and child cohort. Analyses were based on 5079 women in early

4. Androgen deficiency in male patients diagnosed with ANCA-associated vasculitis : A cause of fatigue and reduced health-related quality of life?

NARCIS (Netherlands)

Tuin, Janneke; Sanders, Jan-Stephan F.; Buhl, Birgit M.; van Beek, Andre P.; Stegeman, Coen A.

2013-01-01

Introduction: Low testosterone levels in men are associated with fatigue, limited physical performance and reduced health-related quality of life (HRQOL); however, this relationship has never been assessed in patients with anti-neutrophil cytoplasmic antibodies (ANCA) -associated vasculitides (AAV).

5. Natalizumab treatment reduces fatigue in multiple sclerosis. Results from the TYNERGY trial; a study in the real life setting

DEFF Research Database (Denmark)

Svenningsson, Anders; Falk, Eva; Celius, Elisabeth G;

2013-01-01

Fatigue is a significant symptom in multiple sclerosis (MS) patients. First-generation disease modifying therapies (DMTs) are at best moderately effective to improve fatigue. Observations from small cohorts have indicated that natalizumab, an antibody targeting VLA-4, may reduce MS-related fatigue...

6. Experimental Damage Criterion for Static and Fatigue Life Assessment of Commercial Aluminum Alloy Die Castings

Science.gov (United States)

Battaglia, Eleonora; Bonollo, Franco; Ferro, Paolo

2017-05-01

Defects, particularly porosity and oxides, in high-pressure die casting can seriously compromise the in-service behavior and durability of products subjected to static or cyclic loadings. In this study, the influence of dimension, orientation, and position of casting defects on the mechanical properties of an AlSi12(b) (EN-AC 44100) aluminum alloy commercial component has been studied. A finite element model has been carried out in order to calculate the stress distribution induced by service loads and identify the crack initiation zones. Castings were qualitatively classified on the basis of porosities distribution detected by X-ray technique and oxides observed on fracture surfaces of specimens coming from fatigue and tensile tests. A damage criterion has been formulated which considers the influence of defects position and orientation on the mechanical strength of the components. Using the proposed damage criterion, it was possible to describe the mechanical behavior of the castings with good accuracy.

7. Quality of life, depression and fatigue among persons co-infected with HIV and hepatitis C: outcomes from a population-based cohort.

Science.gov (United States)

Braitstein, P; Montessori, V; Chan, K; Montaner, J S G; Schechter, M T; O'Shaughnessy, M V; Hogg, R S

2005-05-01

The objective of the study was to describe the additional burden generated by hepatitis C (HCV) infection among HIV-infected individuals as measured by self-reported quality of life, depression and fatigue. The provincial HIV/AIDS Drug Treatment Program (DTP) distributes all antiretroviral medication in the province of British Columbia. Eligibility for accessing antiretrovirals is based on published guidelines commensurate with the International AIDS Society. Each participant is asked to complete a self-administered mailed questionnaire that includes patient sociodemographic information, quality of life measures (Medical Outcomes Study-Short Form (MOS-SF), mental health issues (Centre for Epidemiological Studies Depression scale (CESD) and fatigue information. HIV-HCV co-infected individuals were compared to HIV mono-infected individuals using parametric and nonparametric methods. Multivariate logistic regression was used to examine the impact of hepatitis C on quality of life, depression and fatigue, after controlling for sociodemographics and HIV-specific clinical characteristics. Of the 4,134 individuals who were sent a HIV/AIDS DTP survey in 1999, 2000 or 2001, 484 participants both returned one and had an HCV-antibody test result on file. Of the 484 participants eligible for this analysis, 105 (22%) were HCV-positive. In comparison to the 379 (78%) patients testing negative for HCV, a larger proportion of co-infected patients were female (18% versus 3%, plife. However, using multivariate modeling, it was determined that the impact of HCV on quality of life, depression and fatigue was better explained by the sociodemographic factors related to poverty and injection drug use, than by HCV itself. In conclusion, individuals co-infected with HIV and HCV represent a patient population with significant physical and mental health challenges. Although these patients experience poorer quality of life, increased depression and fatigue, this experience appears to be

8. Fatigue Life Prediction for 45 Steel with Given Survivability%给定存活率下45钢的疲劳寿命估算

Institute of Scientific and Technical Information of China (English)

刘嘉; 李静; 杨友社; 李强; 张忠平

2011-01-01

基于临界损伤原理,在以损伤应变范围作为金属材料疲劳裂纹萌生寿命控制参量的基础上,推导了一个新的疲劳裂纹萌生寿命(Fatigue Crack Initation Life,FCIL)估算模型,并给出了模型中始裂抗力系数和始裂门槛值与金属拉伸性能参数之间的关系.与郑氏公式不同,新的FCIL估算模型中疲劳延性指数不恒等于-0.5,而是一个材料常数,用以反映材料抵抗疲劳破坏的能力.以新的FCIL估算模型为基础,建立了含缺口45钢具有给定存活率的疲劳寿命预测公式(PSN曲线公式).与基于郑氏公式的PSN公式相比,新的PSN曲线公式可以更为准确地预测45钢具有给定存活率的疲劳寿命.%Based on the critical damage principle, a new prediction model for fatigue crack initiation life (FCIL) is developed through taking the cyclic damage strain range as the damage parameter. Correlations between the mono-tonic tensile data and two of the material constants (the stress fatigue - resisting coefficient and the theoretical fatigue threshold) in the proposed FCIL prediction model are founded as well. In contrast to Zhengs model, the fatigue ductility exponent contained in the proposed FCIL prediction model is a material constant which doesn't identically equal to the constant value -0.5. Besides, the fatigue ductility exponent shows the damage resistance ability of the material. The expressions of fatigue life curves with given survivability ( PSN curves) for 45 steel notched specimen are developed on the basis of the proposed FCIL predication model. In comparison with the Zhengs model - based PSN curves, the new PSN curves can be used to predict the fatigue life with given survivability of 45 steel better.

9. Structural health monitoring for fatigue life prediction of orthotropic brdige decks

NARCIS (Netherlands)

Pijpers, R.J.M.; Pahlavan, P.L.; Paulissen, J.H.; Hakkesteegt, H.C.; Jansen, T.H.

2013-01-01

Infrastructure asset owners are more and more confronted with structures reaching the end of their structural life. Structural Health Monitoring (SHM) systems should provide up-to-date information about the actual condition, as well predict the structural life and required maintenance of the assets

10. Effect of Thermal Shock Process in Accelerated Environment Spectrum on the Fatigue Life of 7B04-T6 Aluminum Alloy

Institute of Scientific and Technical Information of China (English)

CUI Tengfei; LIU Daoxin; ZHANG Xiaohua; YU Shouming

2016-01-01

The effect of thermal shock, in an accelerated-corrosion environment spectrum, on the fatigue and corrosion behavior of 7B04-T6 aluminum alloy, was determined. The environment spectrum consists of two modules, namely: salt-spray corrosion and thermal shock. The effect of thermal shock on the mechanical properties was determined via tensile tests; SEM, DCS, and XRD were used to determine the effect of thermal shock on the corrosion products. In addition, the corrosion resistance of the products was ascertained through electrochemical testing. The results show that the mechanical properties and fatigue life of the aluminum alloy will decline with prolonged thermal shock time. The thermal shock process may result in denser surface corrosion products than those formed on the no thermal shock specimens, and transformation of some Al (OH)3 into AlOOH. AlOOH may have resulted in improved corrosion resistance and hence a lower decrease in the fatigue life after corrosion, compared with that of the no thermal shock specimen. Repeated corrosion/thermal shock may have delayed further decease in the fatigue life. Therefore, selection of an appropriate equivalent thermal shock temperature and time was essential for designing the environmental spectrum.

11. FATIGUE LIFE, MORPHOLOGICAL STUDIES, AND THERMAL AGING OF RATTAN POWDER-FILLED NATURAL RUBBER COMPOSITES AS A FUNCTION OF FILLER LOADING AND A SILANE COUPLING AGENT

Directory of Open Access Journals (Sweden)

Hanafi Ismail,

2012-01-01

Full Text Available Fatigue life, morphological studies, and thermal aging properties of rattan powder-filled natural rubber (NR composites were investigated as a function of filler loading and a silane coupling agent. NR composites were prepared by the incorporation of rattan powder in the range of 0 to 30 phr into a NR matrix with a laboratory size two roll mill. Thermal aging was carried out for 7 and 14 days at a temperature of 70 °C, and tensile testing was performed in order to determine the aging properties. The results indicated that the fatigue life of rattan powder-filled NR composites decreased with increasing rattan powder loading. Tensile strength and elongation at break decreased whilst tensile modulus, stress at 100% elongation (M100, and stress at 300% elongation (M300 increased after aging. Nevertheless, the addition of the silane coupling agent improved both fatigue life and the aging properties of NR composites due to better adhesion between the rubber matrix and the rattan filler which was confirmed by FTIR studies of composites and SEM studies of fatigue fractured surfaces.

12. Research on Analysis Method of Gear Fatigue Life and Reliability%齿轮弯曲疲劳寿命及可靠性分析研究

Institute of Scientific and Technical Information of China (English)

侯凤国

2012-01-01

Gears are the key components in Transmission system and cheir fatigue life and reliability is very important. In this paper, the gear fatigue life estimation and its reliability are studied by the nominal load method. The metal gear material is defined as structural steel materials, and given the gear load spectrum the study of the gear fatigue life is completed based on the fatigue damage theory Miner.%齿轮是传动系统中的关键部件,对其疲劳寿命及可靠性研究非常重要.采用了名义载荷法完成齿轮疲劳寿命的估算并对其可靠性进行研究.将齿轮材料属性定义为结构钢,给定齿轮工作载荷谱,并基于疲劳损伤理论Miner,完成时齿轮疲劳寿命的研究.

13. Impact of partial versus whole breast radiation therapy on fatigue, perceived stress, quality of life and natural killer cell activity in women with breast cancer

Directory of Open Access Journals (Sweden)

Albuquerque Kevin

2012-06-01

Full Text Available Abstract Introduction This pilot study used a prospective longitudinal design to compare the effect of adjuvant whole breast radiation therapy (WBRT versus partial breast radiation therapy (PBRT on fatigue, perceived stress, quality of life and natural killer cell activity (NKCA in women receiving radiation after breast cancer surgery. Methods Women (N = 30 with early-stage breast cancer received either PBRT, Mammosite brachytherapy at dose of 34 Gy 10 fractions/5 days, (N = 15 or WBRT, 3-D conformal techniques at dose of 50 Gy +10 Gy Boost/30 fractions, (N = 15. Treatment was determined by the attending oncologist after discussion with the patient and the choice was based on tumor stage and clinical need. Women were assessed prior to initiation of radiation therapy and twice after completion of radiation therapy. At each assessment, blood was obtained for determination of NKCA and the following instruments were administered: Perceived Stress Scale (PSS, Functional Assessment of Cancer Therapy-Fatigue (FACT-F, and Functional Assessment of Cancer Therapy-General (FACT-G. Hierarchical linear modeling (HLM was used to evaluate group differences in initial outcomes and change in outcomes over time. Results Fatigue (FACT-F levels, which were similar prior to radiation therapy, demonstrated a significant difference in trajectory. Women who received PBRT reported progressively lower fatigue; conversely fatigue worsened over time for women who received WBRT. No difference in perceived stress was observed between women who received PBRT or WBRT. Both groups of women reported similar levels of quality of life (FACT-G prior to initiation of radiation therapy. However, HLM analysis revealed significant group differences in the trajectory of quality of life, such that women receiving PBRT exhibited a linear increase in quality of life over time after completion of radiation therapy; whereas women receiving WBRT showed a decreasing

14. 航空航天轴承接触疲劳寿命分析%Analysis on Contact Fatigue Life of Aerospace Bearing

Institute of Scientific and Technical Information of China (English)

张明; 李志勇; 崔帅; 冯蕴雯

2012-01-01

A method of analyzing and calculating contact fatigue life of aerospace bearing under arbitrary application load is presented in this paper. The input load data is transformed into stress according to the line-contact stress formula and fatigue equation of constantife. Bringing the stress into the commonly used empirical formula of high cycle fatigue, the amended contact fatigue life under arbitrary application load is obtained. Taking the bearing series MS21438 of the roller wheel track applied in wing flap mechanism as an example, its contact fatigue life is calculaed under its working load. Furthermore, we obtain the conclusion that the service life is prolonged obviously as the model number of bearings increases. The result could provide helpful reference for choosing aerospace bearing designation and confirming bearing ＇s repair cycle.%提出一种航空航天轴承在任意使用载荷下接触疲劳寿命的分析方法。利用线接触应力公式和等寿命转化公式对载荷输入数据进行转化,之后将载荷数据代入到描述高周疲劳的常用经验公式中,经修正得到任意使用载荷下的接触疲劳寿命。以航空航天轴承中的MS21438轴承系列用做襟翼滚轮滑轨运动机构上的滚轮为例,得到此轴承系列在使用载荷下的飞行架次寿命,随轴承选用型号的增大,轴承可使用的飞行架次显著增大。

15. Fatigue behavior of thin-walled grade 2 titanium samples processed by selective laser melting. Application to life prediction of porous titanium implants.

Science.gov (United States)

Lipinski, P; Barbas, A; Bonnet, A-S

2013-12-01

Because of its biocompatibility and high mechanical properties, the commercially pure grade 2 titanium (CPG2Ti) is largely used for fabrication of patient specific implants or hard tissue substitutes with complex shape. To avoid the stress-shielding and help their colonization by bone, prostheses with a controlled porosity are designed. The selective laser melting (SLM) is well adapted to manufacture such geometrically complicated structures constituted by struts with rough surfaces and relatively small diameters. Few studies were dedicated to characterize the fatigue properties of SLM processed samples and bulk parts. They followed conventional or standard protocols. The fatigue behavior of standard samples is very different from the one of porous raw structures. In this study, the SLM made "as built" (AB) and "heat treated" (HT) tubular samples were tested in fatigue. Wöhler curves were determined in both cases. The obtained endurance limits were equal to σD(AB)=74.5MPa and σD(HT)=65.7MPa, respectively. The heat treatment worsened the endurance limit by relaxation of negative residual stresses measured on the external surface of the samples. Modified Goodman diagram was established for raw specimens. Porous samples, based on the pattern developed by Barbas et al. (2012), were manufactured by SLM. Fatigue tests and finite element simulations performed on these samples enabled the determination of a simple rule of fatigue assessment. The method based on the stress gradient appeared as the best approach to take into account the notch influence on the fatigue life of CPG2Ti structures with a controlled porosity. The direction dependent apparent fatigue strength was found. A criterion based on the effective, or global, nominal stress was proposed taking into account the anisotropy of the porous structures. Thanks to this criterion, the usual calculation methods can be used to design bone substitutes, without a precise modelling of their internal fine porosity.

16. International Psychometric Validation of an EORTC Quality of Life Module Measuring Cancer Related Fatigue (EORTC QLQ-FA12).

Science.gov (United States)

Weis, Joachim; Tomaszewski, Krzysztof A; Hammerlid, Eva; Ignacio Arraras, Juan; Conroy, Thierry; Lanceley, Anne; Schmidt, Heike; Wirtz, Markus; Singer, Susanne; Pinto, Monica; Alm El-Din, Mohamed; Compter, Inge; Holzner, Bernhard; Hofmeister, Dirk; Chie, Wei-Chu; Czeladzki, Marek; Harle, Amelie; Jones, Louise; Ritter, Sabrina; Flechtner, Hans-Henning; Bottomley, Andrew

2017-05-01

The European Organisation for Research and Treatment of Cancer (EORTC) Group has developed a new multidimensional instrument measuring cancer-related fatigue to be used in conjunction with the quality of life core questionnaire (EORTC QLQ-C30). The module EORTC QLQ-FA13 assesses physical, cognitive, and emotional aspects of cancer-related fatigue. The methodology follows the EORTC guidelines for phase IV validation of modules. This paper focuses on the results of the psychometric validation of the factorial structure of the module. For validation and cross-validation confirmatory factor analysis (maximum likelihood estimation), intraclass correlation and Cronbach alpha for internal consistency were employed. The study involved an international multicenter collaboration of 11 European and non-European countries. A total of 946 patients with various tumor diagnoses were enrolled. Based on the confirmatory factor analysis, we could approve the three-dimensional structure of the module. Removing one item and reassigning the factorial mapping of another item resulted in the EORTC QLQ-FA12. For the revised scale, we found evidence supporting good local (indicator reliability ≥ 0.60, factor reliability ≥ 0.82) and global model fit (GFI t1|t2 = 0.965/0.957, CFI t1|t2 = 0.976/0.972, RMSEA t1|t2 = 0.060/0.069) for both measurement points. For each scale, test-retest reliability proved to be very good (intraclass correlation: R t1-t2 = 0.905-0.921) and internal consistency proved to be good to high (Cronbach alpha = .79-.90). Based on the former phase III module, the multidimensional structure was revised as a phase IV module (EORTC FA12) with an improved scale structure. For a comprehensive validation of the EORTC FA12, further aspects of convergent and divergent validity as well as sensitivity to change should be determined.

17. Fatigue Life Prediction of Mooring Chains for a Floating Tidal Current Power Station

Institute of Scientific and Technical Information of China (English)

Fengmei Jing; Liang Zhang; Zhong Yang

2012-01-01

As a kind of clean and renewable energy,tidal current energy is becoming increasingly popular all over the world with the shortage of energy and environmental problems becoming more and more severe.A floating tidal current power station is a typical type of tidal current power transformers which can sustain the loads of wind,waves,and current,and even the extreme situation of a typhoon.Therefore,the mooring system must be reliable enough to keep the station operating normally and to survive in extreme situations.The power station examined in this paper was installed at a depth of 40 m.A 44 mm-diameter R4-RQ4 chain was chosen,with a 2 147 kN minimum break strength and 50 kN pretension.Common studless link chain was used in this paper.Based on the Miner fatigue cumulative damage rule,S-N curves of chains,and MOSES software,a highly reliable mooring system was designed and analyzed.The calculation results show that the mooring system designed is reliable throughout a 10-year period.It can completely meet the design requirements of American Petroleum institution (API).Therefore,the presented research is significant for advancing the design of this kind of power station.

18. Quality of life in multiple sclerosis (MS) and role of fatigue, depression, anxiety, and stress: A bicenter study from north of Iran.

Science.gov (United States)

2014-11-01

Although studies have demonstrated significant negative relationships between quality of life (QOL), fatigue, and the most common psychological symptoms (depression, anxiety, stress), the main ambiguity of previous studies on QOL is in the relative importance of these predictors. Also, there is lack of adequate knowledge about the actual contribution of each of them in the prediction of QOL dimensions. Thus, the main objective of this study is to assess the role of fatigue, depression, anxiety, and stress in relation to QOL of multiple sclerosis (MS) patients. One hundred and sixty-two MS patients completed the questionnaire on demographic variables, and then they were evaluated by the Persian versions of Short-Form Health Survey Questionnaire (SF-36), Fatigue Survey Scale (FSS), and Depression, Anxiety, Stress Scale-21 (DASS-21). Data were analyzed by Pearson correlation coefficient and hierarchical regression. Correlation analysis showed a significant relationship between QOL elements in SF-36 (physical component summary and mental component summary) and depression, fatigue, stress, and anxiety (P MS patients. In addition, the findings of this study indirectly suggest that psychological interventions for reducing fatigue, depression, and anxiety can lead to improved QOL of MS patients.

19. Compassion fatigue in nurses.

Science.gov (United States)

Yoder, Elizabeth A

2010-11-01

Compassion fatigue, trigger situations, and coping strategies were investigated in hospital and home care nurses. The Professional Quality of Life Scale measured compassion fatigue, compassion satisfaction, and burnout. Narrative questions elicited trigger situations and coping strategies. Compassion fatigue scores were significantly different between nurses who worked 8- or 12-hour shifts. Fifteen percent of the participants had scores indicating risk of the compassion fatigue. There were significant differences in compassion satisfaction, depending on the unit worked and time as a nurse. The most common category of trigger situations was caring for the patient. Work-related and personal coping strategies were identified. Copyright © 2010 Elsevier Inc. All rights reserved.

20. Improvement in Fatigue, Sleepiness, and Health-Related Quality of Life with Bright Light Treatment in Persons with Seasonal Affective Disorder and Subsyndromal SAD

Directory of Open Access Journals (Sweden)

2011-01-01

Full Text Available Objective. To investigate the effects of bright light treatment for secondary outcome measures and to explore and validate empirically derived subgroups and treatment effects in subgroups. Methods. A descriptive design. A sample of forty-nine persons (mean age of 45.8 with clinically assessed seasonal affective disorder (SAD or subsyndromal SAD (S-SAD participated in a two-group clinical trial evaluating the effects of treatment with bright light therapy. A person-oriented cluster analysis was applied to study treatment effects in subgroups. Results. For the merged group, sleepiness (Epworth Sleepiness Scale, fatigue (fatigue questionnaire, and health-related quality of life (SF-36 were improved at posttreatment, and results were maintained at the one-month followup. Three distinct subgroups had a high level of fatigue in common, while the level of excessive daytime sleepiness and depressed mood differed between the subgroups. Over time, all subgroups improved following ten days treatment in a light room. Conclusion. Fatigue, excessive daytime sleepiness, and health-related quality of life improve in a similar way as depressed mood following treatment with bright light. The treatment was effective irrespective of the severity of the disorder, that is, for persons with SAD and subsyndromal SAD.

1. Crack initiation life in notched Ti-6Al-4V titanium bars under uniaxial and multiaxial fatigue: synthesis based on the averaged strain energy density approach

Directory of Open Access Journals (Sweden)

Giovanni Meneghetti

2017-07-01

Full Text Available The fatigue behaviour of circumferentially notched specimens made of titanium alloy, Ti-6Al-4V, has been analysed. To investigate the notch effect on the fatigue strength, pure bending, pure torsion and multiaxial bending-torsion fatigue tests have been carried out on specimens characterized by two different root radii, namely 0.1 and 4 mm. Crack nucleation and subsequent propagation have been accurately monitored by using the direct current potential drop (DCPD technique. Based on the results obtained from the potential drop technique, the crack initiation life has been defined in correspondence of a relative potential drop increase V/V0 equal to 1%, and it has been used as failure criterion. Doing so, the effect of extrinsic mechanisms operating during crack propagation phase, such as sliding contact, friction and meshing between fracture surfaces, is expected to be reduced. The experimental fatigue test results have been re-analysed by using the local strain energy density (SED averaged over a structural volume having radius R0 and surrounding the notch tip. Finally, the use of the local strain energy density parameter allowed us to properly correlate the crack initiation life of Ti-6Al-4V notched specimens, despite the different notch geometries and loading conditions involved in the tests

2. 空冷风机桥架疲劳寿命分析%Analysis of fatigue life for air-cooling fan bridges

Institute of Scientific and Technical Information of China (English)

徐亚洲; 白国良

2013-01-01

Based on the in-situ tested vibration responses of an air-cooling fan bridge,the dynamic analysis is performed with modulation amplitude disturbing force model of draught fans.Rainflow method is used to count stress cycles and the fatigue load spectrum of air-cooling fan bridges is then programmed combined with investigation results of running frequencies of different operation modes per year.Fatigue damage to the air-cooling fan bridge is calculated in terms of Miner' s cumulative damage rule and design p-S-N curve.After giving the damage threshold corresponding to fatigue failure,the predicted fatigue life of the fan bridge is longer than the designed service life.Furthermore,the fatigue life slightly decreases as effects of mean stress are taken into consideration by Goodman' s,Gerber' s and Soderberg' s models.%基于现场实测风机桥架振动响应,采用风机调幅扰力模型进行结构动力响应分析.根据不同工况下疲劳危险点的名义应力时程,采用雨流计数法和各工况年运行频次调查结果编制疲劳载荷谱.通过Miner损伤累积准则和p-S-N关系对风机桥架进行疲劳损伤分析,给定疲劳破坏的损伤阈值,所得疲劳寿命满足设计使用年限的要求.采用Goodman、Gerber和Soderberg模型考虑平均应力影响时的疲劳寿命略有降低.

3. Surface fatigue life of carburized and hardened M50NiL and AISI 9310 spur gears and rolling-contact test bars

Science.gov (United States)

Townsend, Dennis P.; Bamberger, Eric N.

1989-01-01

Spur gear endurance tests and rolling-element surface tests were conducted to investigate vacuum-induction-melted, vacuum-arc-melted (VIM-VAR) M50NiL steel for use as a gear steel in advanced aircraft applications, to determine its endurance characteristics, and to compare the results with those for standard VAR and VIM-VAR AISI 9310 gear material. Tests were conducted with spur gears and rolling-contact bars manufactured from VIM-VAR M50NiL and VAR and VIM-VAR AISI 9310. The gear pitch diameter was 8.9 cm (3.5 in.). Gear test conditions were an inlet oil temperature of 320 K (116 F), and outlet oil temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), and a speed of 10,000 rpm. Bench rolling-element fatigue tests were conducted at ambient temperatures with a bar speed of 12,500 rpm and a maximum Hertz stress of 4.83 GPA (700 ksi). The VIM-VAR M50NiL gears had a surface fatigue life that was 4.5 and 11.5 times that for VIM-VAR and VAR AISI 9310 gears, respectively. The surface fatigue life of the VIM-VAR M50NiL rolling-contact bars was 13.2 and 21.6 times that for the VIM-VAR and VAR AISI 9310, respectively. The VIM-VAR M50NiL material was shown to have good resistance to fracture through a fatigue spall and to have fatigue life far superior to that of both VIM-VAR and VAR AISI 9310 gears and rolling-contact bars.

4. Effect of corrosion on the fatigue service-life on steel and reinforced concrete beams

NARCIS (Netherlands)

Veerman, R.P.; van Breugel, K.; Koenders, E.A.B.

2015-01-01

Chloride-induced corrosion is a point of big concern in reinforced concrete (RC) structures. To monitor the actual health and to predict the remaining service-life of structures, it is important to understand the structural behaviour and the failure mechanism of structures exposed to chlorides under

5. Effect of corrosion on the fatigue service-life on steel and reinforced concrete beams

NARCIS (Netherlands)

Veerman, R.P.; van Breugel, K.; Koenders, E.A.B.

2015-01-01

Chloride-induced corrosion is a point of big concern in reinforced concrete (RC) structures. To monitor the actual health and to predict the remaining service-life of structures, it is important to understand the structural behaviour and the failure mechanism of structures exposed to chlorides under

6. Quality of life, fatigue and mental health in patients with the m.3243A > G mutation and its correlates with genetic characteristics and disease manifestation.

Science.gov (United States)

Verhaak, Christianne; de Laat, Paul; Koene, Saskia; Tibosch, Marijke; Rodenburg, Richard; de Groot, Imelda; Knoop, Hans; Janssen, Mirian; Smeitink, Jan

2016-03-18

Mitochondrial disorders belong to the most prevalent inherited metabolic diseases with the m.3243A > G mutation reflecting being one of the most common mutations in mitochondrial DNA. Previous studies showed little relationship between mitochondrial genetics and disease manifestation. Relationship between genotype and disease manifestation with patient reported quality of life and other patient reported outcomes is still unexplored. Seventy-two out of the 122 invited adult patients with m.3243A > G mutation completed online standardized questionnaires on quality of life, functional impairment, fatigue and mental health as assessed by the RAND-SF36, the Sickness Impact Profile (SIP), the Checklist Individual Strength (CIS) and the Hospital Anxiety and Depression scale (HADS). Data were related to clinical manifestation reflected by the Newcastle Mitochondrial Disease Adult Scale (NMDAS) score and heteroplasmy levels of the mutation in urine epithelial cells. Patients reported impaired quality of life. Sixty percent showed severe levels of fatigue, and 37% showed clinical relevant mental health problems, which was significantly more than healthy norms. These patient reported health outcomes showed negligible relationship with levels of heteroplasmy (r = life, fatigue and mental health problems, are only partly reflected by clinical assessments. In order to support patients more effectively, integration of patient reported outcomes, alongside symptoms of their disease, in clinical practice is warranted.

7. A STUDY OF FATIGUE LIFE OF ASPHALT CONCRETE BASED ON SHUNGITE MINERAL POWDER

OpenAIRE

D. I. Chernousov; Vl. P. Podolsky; E. V. Trufanov; B. A. Bondarev

2011-01-01

Problem statement. Shortage of mineral powder stimulates seeking of new materials and technologiesby which traditional ones can be replaced without deterioration of their operating properties. Thatis why a study of mineral powder from shungite and development of new technologies of arrangementof high quality and durable asphalt concrete pavement based on shungite is an actual problem.Results. Bearing capacity and service life of asphalt concrete pavement is most completely characterizedby mod...

8. Endurance training in MS: short-term immune responses and their relation to cardiorespiratory fitness, health-related quality of life, and fatigue.

Science.gov (United States)

Bansi, J; Bloch, W; Gamper, U; Riedel, S; Kesselring, J

2013-12-01

The influences of exercise on cytokine response, health-related quality of life (HR-QoL), and fatigue are important aspects of MS rehabilitation. Physical exercises performed within these programs are often practiced in water, but the effects of immersion have not been investigated. To investigate the influences of short-term immune responses and cardiorespiratory fitness on HR-QoL and fatigue during 3 weeks endurance training conducted on a cycle-ergometer or an aquatic-bike. Randomized controlled clinical trial in 60 MS patients. HR-QoL, fatigue, cardiorespiratory fitness, and short-term immune changes (serum concentrations in response to cardiopulmonary exercise test) of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), interleukin-6, and the soluble receptor of IL-6 (sIL-6R) were determined at the beginning and end of 3 weeks of training intervention. Subjects performed daily 30 min training at 60 % of their VO2peak. SF-36 total (p = 0.031), physical (p = 0.004), and mental health (p = 0.057) scores show time effects within both groups. Between-group effects were shown for FSMC total (p = 0.040) and motor function score (p = 0.041). MFIS physical fatigue showed time effects (p = 0.008) for both groups. Linear regression models showed relationships between short-term immune responses and cardiorespiratory fitness with HR-QoL and fatigue after the intervention. This study indicates beneficial effects of endurance training independent of the training setting. Short-term immune adaptations and cardiorespiratory fitness have the potential to influence HR-QoL and fatigue in persons with MS. The specific immune responses of immersion to exercise need further clarification.

9. THE ADVERSE EFFECT OF STEEL PARTICLE CONTAMINANTS ON FATIGUE LIFE OF GREASE LUBRICATED BALL BEARINGS

Directory of Open Access Journals (Sweden)

A. Stathis

2014-01-01

Full Text Available The rating life of ball bearings is reduced when hard particle contaminants are present in the lubricant. Usually, this life reduction is taken into account in the calculation of modified rating life by using the contamination factor through a general characterization of the lubrication conditions. However, the impact of contaminant’s variables such as size, hardness and concentration level has to be specified in detail. This need is resolved by the present work, where greases contaminated with hard steel particles of different sizes are tested with the purpose of finding a pattern in the relationship between steel particle sizes and the progress of wear inside the bearings. A laboratory rig is utilized for these tests and vibration analysis is performed to estimate the condition and the residual life of the bearings. After the tests, optical inspections performed in a stereoscope verify the predictions of vibration analyses. It was found that large contaminating particles, after their initial deformation, produce high stresses and therefore higher wear of the bearings and that the wear mechanism is closely related to the interruption of the lubricating film in such a way that local overheating caused point melting and adhesion of the particles adhered on the raceways. In case of grease contaminated with steel particles, vibration analysis can indicate the severity of wear and monitor its progress. From the conducted tests of the present work it is proved that the size of the contaminant particles affect strongly the wear process in such a way that the larger steel particle contaminants cause greater damage to the bearing. The vibration levels were higher and the damage was greater as particle size increased. It is difficult to establish an equation that describes and quantifies the wear progress involving all the parameters of size and concentration levels of the steel contaminant particles due to the stochastic nature of the wear mechanisms

10. Nonlinear cumulative damage model for multiaxial fatigue

Institute of Scientific and Technical Information of China (English)

SHANG De-guang; SUN Guo-qin; DENG Jing; YAN Chu-liang

2006-01-01

On the basis of the continuum fatigue damage theory,a nonlinear uniaxial fatigue cumulative damage model is first proposed.In order to describe multiaxial fatigue damage characteristics,a nonlinear multiaxial fatigue cumulative damage model is developed based on the critical plane approach,The proposed model can consider the multiaxial fatigue limit,mean hydrostatic pressure and the unseparated characteristic for the damage variables and loading parameters.The recurrence formula of fatigue damage model was derived under multilevel loading,which is used to predict multiaxial fatigue life.The results showed that the proposed nonlinear multiaxial fatigue cumulative damage model is better than Miner's rule.

11. Estrogenic botanical supplements, health-related quality of life, fatigue, and hormone-related symptoms in breast cancer survivors: a HEAL study report

Directory of Open Access Journals (Sweden)

Ma Huiyan

2011-11-01

Full Text Available Abstract Background It remains unclear whether estrogenic botanical supplement (EBS use influences breast cancer survivors' health-related outcomes. Methods We examined the associations of EBS use with health-related quality of life (HRQOL, with fatigue, and with 15 hormone-related symptoms such as hot flashes and night sweats among 767 breast cancer survivors participating in the Health, Eating, Activity, and Lifestyle (HEAL Study. HRQOL was measured by the Medical Outcomes Study short form-36 physical and mental component scale summary score. Fatigue was measured by the Revised-Piper Fatigue Scale score. Results Neither overall EBS use nor the number of EBS types used was associated with HRQOL, fatigue, or hormone-related symptoms. However, comparisons of those using each specific type of EBS with non-EBS users revealed the following associations. Soy supplements users were more likely to have a better physical health summary score (odds ratio [OR] = 1.66, 95% confidence interval [CI] = 1.02-2.70. Flaxseed oil users were more likely to have a better mental health summary score (OR = 1.76, 95% CI = 1.05-2.94. Ginseng users were more likely to report severe fatigue and several hormone-related symptoms (all ORs ≥ 1.7 and all 95% CIs exclude 1. Red clover users were less likely to report weight gain, night sweats, and difficulty concentrating (all OR approximately 0.4 and all 95% CIs exclude 1. Alfalfa users were less likely to experience sleep interruption (OR = 0.28, 95% CI = 0.12-0.68. Dehydroepiandrosterone users were less likely to have hot flashes (OR = 0.33, 95% CI = 0.14-0.82. Conclusions Our findings indicate that several specific types of EBS might have important influences on a woman's various aspects of quality of life, but further verification is necessary.

12. Damage Evolution and Life Prediction of Cross-Ply C/SiC Ceramic-Matrix Composite under Cyclic Fatigue Loading at Room Temperature and 800 °C in Air

Directory of Open Access Journals (Sweden)

Longbiao Li

2015-12-01

Full Text Available The damage evolution and life prediction of cross-ply C/SiC ceramic-matrix composite (CMC under cyclic-fatigue loading at room temperature and 800 °C in air have been investigated using damage parameters derived from fatigue hysteresis loops, i.e., fatigue hysteresis modulus and fatigue hysteresis loss energy. The experimental fatigue hysteresis modulus and fatigue hysteresis loss energy degrade with increasing applied cycles attributed to transverse cracks in the 90° plies, matrix cracks and fiber/matrix interface debonding in the 0° plies, interface wear at room temperature, and interface and carbon fibers oxidation at 800 °C in air. The relationships between fatigue hysteresis loops, fatigue hysteresis modulus and fatigue hysteresis loss energy have been established. Comparing experimental fatigue hysteresis loss energy with theoretical computational values, the fiber/matrix interface shear stress corresponding to different cycle numbers has been estimated. It was found that the degradation rate at 800 °C in air is much faster than that at room temperature due to serious oxidation in the pyrolytic carbon (PyC interphase and carbon fibers. Combining the fiber fracture model with the interface shear stress degradation model and the fibers strength degradation model, the fraction of broken fibers versus the cycle number can be determined for different fatigue peak stresses. The fatigue life S-N curves of cross-ply C/SiC composite at room temperature and 800 °C in air have been predicted.

13. The Recognition Of Fatigue

DEFF Research Database (Denmark)

Elsass, Peter; Jensen, Bodil; Mørup, Rikke;

2007-01-01

Elsass P., Jensen B., Morup R., Thogersen M.H. (2007). The Recognition Of Fatigue: A qualitative study of life-stories from rehabilitation clients. International Journal of Psychosocial Rehabilitation. 11 (2), 75-87......Elsass P., Jensen B., Morup R., Thogersen M.H. (2007). The Recognition Of Fatigue: A qualitative study of life-stories from rehabilitation clients. International Journal of Psychosocial Rehabilitation. 11 (2), 75-87...

14. Advances in Fatigue Life Prediction and Accelerated Test of Rubber Vibration Isolator%橡胶隔振器寿命预测及加速试验研究进展

Institute of Scientific and Technical Information of China (English)

孙伟星; 刘山尖; 欧阳昕; 董兴建

2013-01-01

The failure modes of rubber vibration isolator and the factors influencing its fatigue life were introduced.The fatigue life prediction method for rubber materials based on fracture energy and S-N curve approaches were summarized.The recent research on fatigue life accelerated test for rubber vibration isolator was presented and the current development trends in rubber fatigue life prediction were prospected.%介绍了橡胶材料的疲劳失效形式及影响橡胶材料抗疲劳性能的因素,总结了基于撕裂能和基于S-N曲线的橡胶材料疲劳寿命预测方法,阐明了橡胶隔振器加速试验研究的现状,展望了未来值得研究的方向.

15. Contact Stress Analysis and Fatigue Life Prediction of a Turbine Fan Disc

Science.gov (United States)

Yang, Liang; Zhu, Shun-Peng; Lv, Zhiqiang; Zuo, Fang-Jun; Huang, Hong-Zhong

2016-06-01

Fan discs are critical components of an aero engine. In this paper, contact stress and life prediction of a turbine fan disc were investigated. A simplified pin/disc model was conducted to simulate the practical working condition under applied loads using finite element (FE) analysis. This study is devoted to examining the effects of interface condition of pin/disc such as gap and coefficient upon the maximum stress. The FE model indicated that the maximum stress occurs at the top right corner in the second pin hole, and larger gap or friction coefficient has a significant effect on the maximum stress. In addition, FE analysis without considering friction is also conducted. The results show that the dangerous point is similar to the result which considers friction and the stress state is relatively larger than that of considering friction. Finally, based on FE analysis result, life prediction for the fan disc is conducted to combine the material S-N curve, mean stress effects and concentration stress factor obtained by means of FE method.

16. Thermo-fatigue life study on LCCC electronic packaging structure%LCCC电子封装结构的热疲劳寿命分析

Institute of Scientific and Technical Information of China (English)

侯传涛; 童军; 荣克林

2014-01-01

以典型LCCC电子封装结构为研究对象，分别基于有限元仿真分析方法和工程算法开展电子封装结构在温循载荷作用下的疲劳寿命分析，分析结果表明，有限元仿真分析方法和工程算法所预测的结构疲劳寿命一致性较好。所探索的有限元方法和工程估算方法在解决电子封装结构的热疲劳寿命问题时具有很好地推广性。%Basing on the FEM and theory methods, Thermo-fatigue life of LCCC electronic packaging structure is investigated. The analysis outcomes show that the Fatigue life predicated by FEM is associated with the result of the theory method. The techniques explored by this paper are extended conveniently to evaluate thermo-fatigue life for other electronic packaging structures.

17. 挤压AZ31B镁合金多轴疲劳寿命预测%MULTIAXIAL FATIGUE LIFE PREDICTION FOR EXTRUDED AZ31B MAGNESIUM ALLOY

Institute of Scientific and Technical Information of China (English)

熊缨; 程利霞

2012-01-01

采用挤压AZ31B镁合金薄壁圆筒试样,分别进行了单轴和多轴加载下的对称应变控制疲劳实验,研究了不同加载路径对疲劳寿命的影响.单轴加载包括对称拉压和扭转路径,多轴加载包括45°比例加载和90°非比例加载路径.结果表明,在加载的等效应变幅值为0.3％ 0.55％附近,4种加载路径下的应变-寿命曲线均出现了不连续的拐点；比例加载路径在等效应变幅大于0.45％时疲劳寿命最高,拉压路径在等效应变幅小于0.45％时疲劳寿命最高；非比例加载路径的疲劳寿命最低.使用基于临界平面法的多轴疲劳模型FS,SWT以及修正SWT分别预测了各个路径加载下的疲劳寿命.预测结果表明,SWT模型对于拉压和循环扭转加载下寿命预测结果误差较大；FS模型与修正SWT模型可以较好地预测挤压AZ31B镁合金各个路径加载下的疲劳寿命.%Magnesium alloy components were widely used in automobile and aircraft industries, due to their light weight, high specific strength, stiffness, damping capacity, machinability, and recyclability. Engineering components subjected cyclic loading inevitably and led to fatigue failure. Most studies on magnesium alloy were focus on uniaxial fatigue, very limited work has been done of magnesium alloys under multiaxial loading. In this study, strain-controlled multiaxial fatigue experiments were conducted on extruded AZ31B magnesium alloy using thin-walled tubular specimens in ambient air. Four loading paths, including fully reversed tension-compression, cyclic torsion, 45° in-phase axial-torsion and 90° out-of-phase axial-torsion, were adopted in the fatigue experiments. It is observed that the strain-life curve displays a distinguishable kink under each loading path at the equivalent strain amplitude around 0.3% to 0.55%. The fatigue life -under the proportional loading path is the highest when equivalent strain amplitudes higher than 0.45%, and the fatigue

18. 'Setting a principled boundary'? Euthanasia as a response to 'life fatigue'.

Science.gov (United States)

Huxtable, Richard; Möller, Maaike

2007-03-01

The Dutch case of Brongersma presents novel challenges to the definition and evaluation of voluntary euthanasia since it involved a doctor assisting the suicide of an individual who was (merely?) 'tired of life'. Legal officials had called on the courts to 'set a principled boundary', excluding such cases from the scope of permissible voluntary euthanasia, but they arguably failed. This failure is explicable, however, since the case seems justifiable by reference to the two major principles in favour of that practice, respect for autonomy and beneficence. Ultimately, it will be argued that those proponents of voluntary euthanasia who are wary of its use in such circumstances may need to draw upon 'practical' objections, in order to erect an otherwise arbitrary perimeter. Furthermore, it will be suggested that the issues raised by the case are not peculiarly Dutch in nature and that, therefore, there are lessons here for other jurisdictions too.

19. Study on the Fatigue Life of Steel Crane Structures in Service%在役钢结构吊车梁疲劳寿命研究

Institute of Scientific and Technical Information of China (English)

张琳

2012-01-01

In recent years, according to the survey of industrial plant, most of the crane steel crane beam with large tonnage, heavy grade level or overweight duty prematurely appeared different degree of fatigue crack under the action of repeated load, and endanger the safety in production. So the fatigue life of crane beam structure is usually considered as the major indexes of the safety control. The evaluation parameters and index of fatigue life is great different from the practical load, and the structure form, stress state, production process of crane beam are the main factors that influence the fatigue life. At present, the technology personnel has done further research to the basic theory of the fatigue life of steel crane beam and has put forward a variety of evaluation methods. But we can see that each evaluation method has some limitations, and there is no better assessment method. Therefore, to seek a more reasonable evaluation method so as to more accurately calculate the fatigue life of crane beam is very necessary. This paper mainly uses the details fatigue rating method (DFR method) to calculate the fatigue life of steel crane beam.%近年来,对工业厂房的调查结果显示,大吨位、重级或超重级工作制起重机的钢吊车梁在反复荷载的作用下,大部分均过早地出现了不同程度的疲劳裂缝,危害生产安全.因此通常将吊车梁结构的疲劳寿命作为控制安全性的主要指标.疲劳寿命的评估参数及指标和实际的荷载存在较大的差异,还有吊车梁的结构形式、受力状态、制作工艺都是影响疲劳寿命的主要因素.目前已有技术人员对钢结构吊车梁疲劳寿命的基本理论进行了深入的研究且提出了多种评估方法,但每种评估方法都有一定的局限性,而且目前尚缺乏较好的评估方法.因此,寻求一个更加合理的评估方法以期能较准确地计算吊车梁的疲劳寿命就显得十分必要.本文主要采用细节疲劳

20. Fatigue Life Simulation Design and Research of the Taper Leaf Spring on Automobile%汽车少片变截面板簧的疲劳寿命仿真设计

Institute of Scientific and Technical Information of China (English)

朱剑宝; 陈建宏; 林平

2011-01-01

利用基于非线性有限元仿真分析的疲劳设计方法,对少片变截面板簧进行了疲劳寿命试验仿真分析,确定出板簧的疲劳破坏发生区域,然后基于材料的S-N曲线,利用ANSYS疲劳分析模块进行板簧的疲劳寿命设计计算.该疲劳寿命分析方法可以较准确地得出板簧产品的疲劳寿命,节约了疲劳试验成本.%By using the fatigue life prediction method based on the non-linear finite element model, fatigue life test simulation analysis of the designed taper leaf spring in the paper are performed, then based on the S-N curve of material, detect the fatigue dangerous area and predict fatigue life of the structure in critical location with the help of ANSYS’ Fatigue module, it is feasible to predict fatigue life of leafspring product, reduce fatigue test costs, provide practical significance in engineering.

1. 核电汽轮机转子在低周疲劳与高周疲劳交互作用下裂纹扩展寿命的研究%Study on Crack Propagation Life under Low Cycle Fatigue and High Cycle Fatigue of Nuclear Steam Turbine Rotors

Institute of Scientific and Technical Information of China (English)

史进渊

2015-01-01

The calculation and assessment methods for the crack propagation life under low cycle fatigue and high cycle fatigue of nuclear steam turbine rotors is presented. The low high fatigue cycle stress amplitude and stress range as well as the crack propagation life calculation methods for low cycle fatigue and high cycle fatigue of nuclear steam turbine rotors are introduced. The calculation and assessment methods for the crack propagation calendar life under low cycle fatigue and high cycle fatigue of nuclear steam turbine rotors are given together with an application example for calculation and improvement of the fatigue crack propagation calendar life of a low pressure welded rotor for 1 000 MW nuclear steam turbines. The example results indicate that effect of the high cycle fatigue on the fatigue crack propagation calendar life of nuclear steam turbine rotors is bigger, it is necessary that assessment for the crack propagation life under low cycle fatigue and high cycle fatigue of rotors in the rotor structure design of new development for nuclear steam turbine and the rotor safety assessment for operation steam turbine for nuclear power plants.%提出核电汽轮机转子在低周疲劳与高周疲劳交互作用下裂纹扩展寿命的计算与评定方法.介绍核电汽轮机转子的低周疲劳与高周疲劳的应力幅与应力范围、低周疲劳裂纹扩展寿命与高周疲劳扩展寿命的计算方法.给出了核电汽轮机转子在低周疲劳与高周疲劳交互作用下裂纹扩展日历寿命的计算与评定方法,以及1 000 MW级核电汽轮机焊接低压转子疲劳裂纹扩展日历寿命的计算与改进的应用实例.结果表明,高周疲劳对汽轮机转子疲劳裂纹扩展日历寿命有比较大的影响,新研制核电汽轮机的转子结构设计和在役核电汽轮机的转子安全性评定,需要评估转子在低周疲劳与高周疲劳交互作用下裂纹扩展寿命.

2. Decay in chest compression quality due to fatigue is rare during prolonged advanced life support in a manikin model

Directory of Open Access Journals (Sweden)

2011-08-01

Full Text Available Abstract Background The aim of this study was to measure chest compression decay during simulated advanced life support (ALS in a cardiac arrest manikin model. Methods 19 paramedic teams, each consisting of three paramedics, performed ALS for 12 minutes with the same paramedic providing all chest compressions. The patient was a resuscitation manikin found in ventricular fibrillation (VF. The first shock terminated the VF and the patient remained in pulseless electrical activity (PEA throughout the scenario. Average chest compression depth and rate was measured each minute for 12 minutes and divided into three groups based on chest compression quality; good (compression depth ≥ 40 mm, compression rate 100-120/minute for each minute of CPR, bad (initial compression depth 120/minute or decay (change from good to bad during the 12 minutes. Changes in no-flow ratio (NFR, defined as the time without chest compressions divided by the total time of the ALS scenario over time was also measured. Results Based on compression depth, 5 (26%, 9 (47% and 5 (26% were good, bad and with decay, respectively. Only one paramedic experienced decay within the first two minutes. Based on compression rate, 6 (32%, 6 (32% and 7 (37% were good, bad and with decay, respectively. NFR was 22% in both the 1-3 and 4-6 minute periods, respectively, but decreased to 14% in the 7-9 minute period (P = 0.002 and to 10% in the 10-12 minute period (P Conclusions In this simulated cardiac arrest manikin study, only half of the providers achieved guideline recommended compression depth during prolonged ALS. Large inter-individual differences in chest compression quality were already present from the initiation of CPR. Chest compression decay and thereby fatigue within the first two minutes was rare.

3. The impact of poverty, chronic illnesses, and health insurance status on out-of-pocket health care expenditures in later life.

Science.gov (United States)

Kim, Jinhyun; Richardson, Virginia

2014-10-01

This study aims to examine poverty, chronic illnesses, health insurance, and health care expenditures, within the context of a political economy of aging perspective. Subsamples of 1,773 older adults from the Medical Expenditure Panel Survey were selected for analyses. The results showed that chronic illnesses influenced out-of-pocket health care costs. Older persons with more than one health insurance spent less on out-of-pocket health care costs. The results have implications for health care social workers concerned with the growing costs of chronic illnesses, implementing integrated care, and advocating for extending public health insurance coverage especially for our most impoverished older adults.

4. Compressive Fatigue in Wood

DEFF Research Database (Denmark)

Clorius, Christian Odin; Pedersen, Martin Bo Uhre; Hoffmeyer, Preben;

1999-01-01

An investigation of fatigue failure in wood subjected to load cycles in compression parallel to grain is presented. Small clear specimens of spruce are taken to failure in square wave formed fatigue loading at a stress excitation level corresponding to 80% of the short term strength. Four...... frequencies ranging from 0.01 Hz to 10 Hz are used. The number of cycles to failure is found to be a poor measure of the fatigue performance of wood. Creep, maximum strain, stiffness and work are monitored throughout the fatigue tests. Accumulated creep is suggested identified with damage and a correlation...... is observed between stiffness reduction and accumulated creep. A failure model based on the total work during the fatigue life is rejected, and a modified work model based on elastic, viscous and non-recovered viscoelastic work is experimentally supported, and an explanation at a microstructural level...

5. Fatigue life and damage evolution of martensitic steels for low-pressure steam turbine blades in the VHCF regime; Lebensdauer und Schaedigungsentwicklung martensitischer Staehle fuer Niederdruck-Dampfturbinenschaufeln bei Ermuedungsbeanspruchung im VHCF-Bereich

Energy Technology Data Exchange (ETDEWEB)

Kovacs, Stephan

2014-07-01

Low-pressure steam turbine blades are usually made of martensitic steels with Cr contents between 9 and 12%, which combine good corrosion resistance, high mechanical strength and sufficient ductility. The inhomogeneous flow field behind the vanes generates high-frequency oscillations above 1 kHz. In addition, the blades with lengths up to 1.5 m are operated at rotational speeds up to 3000 rpm, resulting in large centrifugal forces leading to the superposition of extremely high mean stresses. Also resonance oscillations during start-up and shutdown cannot be completely excluded. Currently, the components are designed using high safety factors against S-N curves with an assumed asymptotic fatigue limit above 107 load cycles. Nevertheless, fatigue cracks are observed even at high number of cycles, starting from the blade root without pre-damage by erosion or steam droplet impingement. While fatigue failure usually occurs at the surface, fatigue cracks at very high number of cycles (> 108) initiate at oxides or intermetallic inclusions below the surface. This transition between both failure mechanisms in the Very High-Cycle Fatigue (VHCF) regime is in the focus of numerous current research activities, because numbers of cycles above 108 can be attained in a viable period of time using the recently developed high-frequency testing techniques operated at 20 kHz. Also for wind turbines, gas turbines, bearings, springs, etc. VHCF issues become increasingly important. Within this work, the fatigue life and damage behavior of a martensitic Cr-steel during fatigue loading with and without high mean stresses at number of cycles to failure above 108 was analyzed. On the one hand, the studies gave insights into the relation between fatigue life and fatigue damage evolution of the investigated group of high-strength steels in the very high cycle fatigue regime (up to 2·109). In particular, the influence of high mean stresses on the VHCF behavior (fracture origin, crack growth

6. Probabilistic Fatigue Damage Program (FATIG)

Science.gov (United States)

Michalopoulos, Constantine

2012-01-01

FATIG computes fatigue damage/fatigue life using the stress rms (root mean square) value, the total number of cycles, and S-N curve parameters. The damage is computed by the following methods: (a) traditional method using Miner s rule with stress cycles determined from a Rayleigh distribution up to 3*sigma; and (b) classical fatigue damage formula involving the Gamma function, which is derived from the integral version of Miner's rule. The integration is carried out over all stress amplitudes. This software solves the problem of probabilistic fatigue damage using the integral form of the Palmgren-Miner rule. The software computes fatigue life using an approach involving all stress amplitudes, up to N*sigma, as specified by the user. It can be used in the design of structural components subjected to random dynamic loading, or by any stress analyst with minimal training for fatigue life estimates of structural components.

7. Perceived work ability, quality of life, and fatigue in patients with rheumatoid arthritis after a 6-month course of TNF inhibitors: prospective intervention study and partial economic evaluation.

Science.gov (United States)

Hoving, J L; Bartelds, G M; Sluiter, J K; Sadiraj, K; Groot, I; Lems, W F; Dijkmans, B A C; Wijbrandts, C A; Tak, P P; Nurmohamed, M T; Voskuyl, A E; Frings-Dresen, M H W

2009-01-01

The objective of this exploratory study was to evaluate the effects and costs of a 6-month course of tumour necrosis factor (TNF) inhibitors on work ability, quality of life, and fatigue in patients with rheumatoid arthritis (RA). In this prospective single-arm intervention study 59 consecutive patients of working age with established RA were recruited from an outpatient clinic in Amsterdam, the Netherlands. All patients received fortnightly subcutaneous injections of 40 mg adalimumab. The three outcomes at baseline and 6 months were: perceived work ability [Work Ability Index (WAI)], quality of life [Rheumatoid Arthritis Quality of Life instrument (RAQoL)], and fatigue [Checklist Individual Strength (CIS), Need for Recovery (NFR) scale]. Cost data of the preceding 6 months were collected using a self-administered patient questionnaire at baseline and follow-up. At 6 months, all outcomes showed a statistically significant improvement in mean scores from baseline, ranging from 10.0% (WAI), to 11.7% (RAQoL), to 15% (NFR) (subgroup paid work, n = 26). The total mean costs showed a twofold increase in mean costs per week per patient [difference EUR 169, 95% confidence interval (CI) EUR 113-226]. In this short-term exploratory evaluation, a 6-month course of TNF inhibitors improved work ability and quality of life, and reduced fatigue in patients with established RA. These effects are associated with an increase in total healthcare costs, attributable to the costs of TNF inhibitors. Randomized controlled trials with a longer follow-up are needed to show a long-term effect on work disability and the potential cost-effectiveness of TNF inhibitors.

8. Supervised exercise reduces cancer-related fatigue: a systematic review

Directory of Open Access Journals (Sweden)

José F Meneses-Echávez

2015-01-01

Full Text Available Question: Does supervised physical activity reduce cancer-related fatigue? Design: Systematic review with meta-analysis of randomised trials. Participants: People diagnosed with any type of cancer, without restriction to a particular stage of diagnosis or treatment. Intervention: Supervised physical activity interventions (eg, aerobic, resistance and stretching exercise, defined as any planned or structured body movement causing an increase in energy expenditure, designed to maintain or enhance health-related outcomes, and performed with systematic frequency, intensity and duration. Outcome measures: The primary outcome measure was fatigue. Secondary outcomes were physical and functional wellbeing assessed using the Functional Assessment of Cancer Therapy Fatigue Scale, European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire, Piper Fatigue Scale, Schwartz Cancer Fatigue Scale and the Multidimensional Fatigue Inventory. Methodological quality, including risk of bias of the studies, was evaluated using the PEDro Scale. Results: Eleven studies involving 1530 participants were included in the review. The assessment of quality showed a mean score of 6.5 (SD 1.1, indicating a low overall risk of bias. The pooled effect on fatigue, calculated as a standardised mean difference (SMD using a random-effects model, was –1.69 (95% CI –2.99 to –0.39. Beneficial reductions in fatigue were also found with combined aerobic and resistance training with supervision (SMD = –0.41, 95% CI –0.70 to –0.13 and with combined aerobic, resistance and stretching training with supervision (SMD = –0.67, 95% CI –1.17 to –0.17. Conclusion: Supervised physical activity interventions reduce cancer-related fatigue. These findings suggest that combined aerobic and resistance exercise regimens with or without stretching should be included as part of rehabilitation programs for people who have been diagnosed with cancer

9. Fatigue damage analysis and life prediction for vehicle control arm%车辆控制臂疲劳损伤分析与寿命预测

Institute of Scientific and Technical Information of China (English)

刘永臣; 王国林; 孙丽

2013-01-01

为提高车辆结构疲劳耐久性、完善车辆结构设计方法，该文对车辆控制臂进行了的疲劳损伤分析与寿命预测研究。通过有限元分析法，建立控制臂有限元分析模型，分析其结构应力，确定疲劳损坏热点。实测获得试验场条件下控制臂的应变载荷，进行频谱分析与低通滤波等数据处理，利用雨流计数法，编制控制臂载荷谱。利用局部应力应变法与Miner准则，考虑结构应力集中修正，完成控制臂的疲劳损伤分析与寿命预估。结果表明，控制臂损伤热点主要分布在与转向节连接的过渡处，控制臂载荷信号频域能量主要集中在15 Hz以内，与车体结构的实际频率分布相符，控制臂的疲劳损伤分布与实际路况条件的受力状况相符，得出控制臂试验场预期寿命为3.96万h。研究结果可为车辆疲劳耐久研究提供重要参考。%In order to improve the vehicle structure fatigue durability, and to perfect vehicle structure design method, In this paper, fatigue damage analysis and life prediction on the vehicle control arm were done by three parts, namely, finite element modeling and analysis, load spectrum testing and establishment, fatigue damage analysis and life prediction. A fatigue life prediction method of vehicle control arm was put forward. Firstly, the finite element analysis model of the vehicle control arm was built in ANSYS software, and its construction stress was calculated and analyzed under the action of lateral and longitudinal forces respectively. Two hot points on the control arm were determined, which could bring about fatigue damage. The location of each hot point is respectively at the transition of the control arm connected to the steering knuckle and to the subframe. Both locations were identified as load testing points of P1 and P2 that strain gauges were pasted. Secondly, the strain load of the control arm was measured under the condition

10. Fatigue evaluation algorithms: Review

Energy Technology Data Exchange (ETDEWEB)

Passipoularidis, V.A.; Broendsted, P.

2009-11-15

A progressive damage fatigue simulator for variable amplitude loads named FADAS is discussed in this work. FADAS (Fatigue Damage Simulator) performs ply by ply stress analysis using classical lamination theory and implements adequate stiffness discount tactics based on the failure criterion of Puck, to model the degradation caused by failure events in ply level. Residual strength is incorporated as fatigue damage accumulation metric. Once the typical fatigue and static properties of the constitutive ply are determined,the performance of an arbitrary lay-up under uniaxial and/or multiaxial load time series can be simulated. The predictions are validated against fatigue life data both from repeated block tests at a single stress ratio as well as against spectral fatigue using the WISPER, WISPERX and NEW WISPER load sequences on a Glass/Epoxy multidirectional laminate typical of a wind turbine rotor blade construction. Two versions of the algorithm, the one using single-step and the other using incremental application of each load cycle (in case of ply failure) are implemented and compared. Simulation results confirm the ability of the algorithm to take into account load sequence effects. In general, FADAS performs well in predicting life under both spectral and block loading fatigue. (author)

11. A Preliminary Path Analysis: Effect of Psychopathological Symptoms, Mental and Physical Dysfunctions Related to Quality of Life and Body Mass Index on Fatigue Severity of Iranian Patients with Multiple Sclerosis

Directory of Open Access Journals (Sweden)

Ghasem Salehpoor

2012-07-01

Full Text Available Background: Multiple sclerosis (MS is a neurological disease with fatigue as most prevalent symptom. Psychopathological symptoms, physical and mental dysfunctions and body mass abnormalities potentially could deteriorate fatigue. Thus, in this study, we aimed at evaluating the effect of these factors on fatigue severity of MS patients.Methods: In this cross‐sectional study, 162 patients with mean age of 34.1 ± 9.4 (16-58 years were recruited by consecutive sampling. All the patients, after completing demographic information were evaluated using Persian versions of Fatigue Severity Scale (FSS, depression, anxiety and stress scale (DASS-21, and short form Health Survey Questionnaire (SF-36.Results: Correlation analysis showed a significant relationship between fatigue severity and depression, anxiety, stress, physical component summary (PCS and mental component summary (MCS (P < 0.01. Findings of path analysis demonstrated that PCS is the only variable which has a direct effect on fatigue severity(β = -0.278, P < 0.05. Moreover, the strongest standard coefficient (β belonged to cause and effect relationship between MCS and depression (β = -0.691, P < 0.0001.Conclusion: Present study made the role of psychopathological symptoms and physical and mental dysfunctions prominent in exacerbation of fatigue severity. Moreover, we can refer to more sensible effect of physical dysfunction related to life on fatigue

12. EFFECT OF SPECIMEN ASPECT RATIO ON FATIGUE LIFE OF CLOSED CELL Al-Si-Ca ALLOY FOAM

Institute of Scientific and Technical Information of China (English)

Amkee Kim; Ilhyun Kim

2008-01-01

Quasi-static and compressive fatigue tests on the closed cell Al-Si-Ca alloy foam specimens with three different aspect ratios were performed.It turned out that the onset of cyclic shortening of foam with a lower aspect ratio took place earlier and the fatigue strength was lower compared with the specimen with a higher aspect ratio,although aU the dimensions of specimen satisfied the seven times the cell size criterion,while the quasi-static stress-strain curves were almost same having same Young's modulus,yield stress and plateau stress.Therefore,the seven times the cell size criterion for the quasi-static compression behavior was not applicable to the fatigue analysis of Al-Si-Ca alloy foam.

13. Effects of Ultrasonics-Assisted Face Milling on Surface Integrity and Fatigue Life of Ni-Alloy 718

Science.gov (United States)

Suárez, Alfredo; Veiga, Fernando; de Lacalle, Luis N. López; Polvorosa, Roberto; Lutze, Steffen; Wretland, Anders

2016-09-01

This work investigates the effects of ultrasonic vibration-assisted milling on important aspects such us material surface integrity, tool wear, cutting forces and fatigue resistance. As an alternative to natural application of ultrasonic milling in brittle materials, in this study, ultrasonics have been applied to a difficult-to-cut material, Alloy 718, very common in high-temperature applications. Results show alterations in the sub-superficial part of the material which could influence fatigue resistance of the material, as it has been observed in a fatigue test campaign of specimens obtained with the application of ultrasonic milling in comparison with another batch obtained applying conventional milling. Tool wear pattern was found to be very similar for both milling technologies, concluding the study with the analysis of cutting forces, exhibiting certain improvement in case of the application of ultrasonic milling with a more stable evolution.

14. Effects of Ultrasonics-Assisted Face Milling on Surface Integrity and Fatigue Life of Ni-Alloy 718

Science.gov (United States)

Suárez, Alfredo; Veiga, Fernando; de Lacalle, Luis N. López; Polvorosa, Roberto; Lutze, Steffen; Wretland, Anders

2016-11-01

This work investigates the effects of ultrasonic vibration-assisted milling on important aspects such us material surface integrity, tool wear, cutting forces and fatigue resistance. As an alternative to natural application of ultrasonic milling in brittle materials, in this study, ultrasonics have been applied to a difficult-to-cut material, Alloy 718, very common in high-temperature applications. Results show alterations in the sub-superficial part of the material which could influence fatigue resistance of the material, as it has been observed in a fatigue test campaign of specimens obtained with the application of ultrasonic milling in comparison with another batch obtained applying conventional milling. Tool wear pattern was found to be very similar for both milling technologies, concluding the study with the analysis of cutting forces, exhibiting certain improvement in case of the application of ultrasonic milling with a more stable evolution.

15. Helicopter Fatigue Life Assessment

Science.gov (United States)

1981-03-01

de reproduire d’eventuels effets retard de la propagation dus aux changements de niveaux de contraintes) (Voir spectre de charges tableau II fig :8...configurations rencontr6es dans un vol type d’une heura. Certaines de ces configurations, combinges aux sollicitations dynamiques, pauvent avoir un effet ...vitesse la pluG rapide de propagation 6tait de 2 mmn pour 100 heures. La p~riodicit6 des contr~les est suffisa- ment serr ~e pour que l’endommagement

16. The need to generate realistic strain signals at an automotive coil spring for durability simulation leading to fatigue life assessment

Science.gov (United States)

Putra, T. E.; Abdullah, S.; Schramm, D.; Nuawi, M. Z.; Bruckmann, T.

2017-09-01

This study aims to accelerate fatigue tests using simulated strain signals. Strain signals were acquired from a coil spring involving car movements. Using a mathematical expression, the measured strain signals yielded acceleration signals, and were considered as disturbances on generating strain signals. The simulated strain signals gave the testing time deviation by only 1.5%. The wavelet-based data editing was applied to shorten the strain signals time up to 36.7% and reduced the testing time up to 33.9%. In conclusion, the simulated strain signals were able to maintain the majority of fatigue damage and decreased the testing time.

17. Fatigue life assessment of thin-walled welded joints under non-proportional load-time histories by the shear stress rate integral approach

Directory of Open Access Journals (Sweden)

A. Bolchoun

2016-10-01

Full Text Available Fatigue life tests under constant and variable amplitude loadings were performed on the tube-tube thin-walled welded specimens made of magnesium (AZ31 and AZ61 alloys. The tests included pure axial, pure torsional and combined in-phase and out-of-phase loadings with the load ratio  RR " ", " " 1  . For the tests with variable amplitude loads a Gaußdistributed loading spectrum with S L 4 5 10  cycles was used. Since magnesium welds show a fatigue life reduction under out-of-phase loads, a stress-based method, which takes this behavior into account, is proposed. The out-of-phase loading results in rotating shear stress vectors in the section planes, which are not orthogonal to the surface. This fact is used in order to provide an out-of-phase measure of the load. This measure is computed as an area covered by the shear stress vectors in all planes over a certain time interval, its computation involves the shear stress and the shear stress rate vectors in the individual planes. Fatigue life evaluation for the variable amplitudes loadings is performed using the Palmgren-Miner linear damage accumulation, whereas the total damage of every cycle is split up into two components: the amplitude component and the out-of-phase component. In order to compute the two components a modification of the rainflow counting method, which keeps track of the time intervals, where the cycles occur, must be used. The proposed method also takes into account different slopes of the pure axial and the pure torsional Wöhler-line by means of a Wöhler-line interpolation for combined loadings

18. Reiki efficacy of therpy in improving pain, fatigue, quiality of life and its impact on activities´s of women daily living suffering from fibromyalgia

Directory of Open Access Journals (Sweden)

Lourdes Casillas Santamaría

2013-01-01

Full Text Available Objective: The evaluation the Reiki therapy effectiveness to relieve pain, fatigue and its impact on activities´s of women daily living suffering from fibromyalgia.Methods: A controlled clinical trial, randomized to three groups (Reiki therapy, placebo and control and hiding of random distribution. Subjects: 150 women, over 18 years, diagnosed with fibromyalgia, according to the American College of Rheumatology (ACR, diagnosed for more than a year and signing the informed consent. It will exclude those with mental or cognitive impairment that could impede their participation. Scope: Fibromyalgia Association of Madrid, with a record 2,500 members, with headquarters in downtown Madrid. Intervention: Standardization of Reiki therapy’s interventions, and placebo control. Reiki therapy will be applied by a solo Reiki Master, the placebo group will be attended by one solo nurse with no experience of touch therapy, simulating touches points of energy in the body; the control group receive no intervention. It will be 4 weekly sessions of 60 minutes in the case of Reiki and placebo groups. Participants in the control group will have to go to school to complete the questionnaires in the same periods of time. Variables (measuring instruments: main outcome variable: pain. It will be collected data on pain throughout the study (VAS, fatigue (VAS, quality of life (SF-36 and disease impact on activities of daily living (FIQ at various times: at the studio’s beginning (baseline, after a month and 3 months later. Sociodemographic and clinical variables will be collected also. Analysis: It will be made by allocated treatment (intention to treat. Comparisons shall be made of pain, fatigue, quality of life and disease’s impact on daily life activities among the three groups. Statistical analysis was done by analysis of variance.

19. 表面裂纹疲劳扩展寿命可靠性分析%Reliability Analysis for Fatigue Propagation Life of Surface Crack

Institute of Scientific and Technical Information of China (English)

孙鹏飞; 袁杰红

2011-01-01

A method for reliability analysis for fatigue propagation life of surface crack is presented based on the line - spring model and Paris formula. Aiming at inefficiency of direct Monte Carlo method, latin hypercube sampling (LHS) method was used for random sampling so as to improve convergent velocity of calculation. The fatigue life is obtained at the given reliability and the reliability is obtained at the given life, in consideration of the uncertainty and correlation of parameters such as the crack size, cycle loading and fatigue parameters. The results of example accord with the existing results. The present method is effective and universal for engineering application.%在线弹簧模型和Paris公式的基础上，提出了对表面裂纹疲劳扩展寿命进行可靠性分析的方法。针对直接Monte Carlo法效率较低的问题，采用拉丁超立方法(LHS)进行随机抽样，以提高计算的收敛速度。考虑裂纹几何尺寸、交变载荷和疲劳参数等的随机性及相关性，求得了给定可靠度下的疲劳寿命和给定寿命下的可靠度。本文结果与已有文献结果具有较好的一致性。该方法简便有效、通用性强，适合于工程应用。

20. The Health-Related Quality of Life for Patients with Myalgic Encephalomyelitis / Chronic Fatigue Syndrome (ME/CFS.

Directory of Open Access Journals (Sweden)

Michael Falk Hvidberg

Full Text Available Myalgic encephalomyelitis (ME/chronic fatigue syndrome (CFS is a common, severe condition affecting 0.2 to 0.4 per cent of the population. Even so, no recent international EQ-5D based health-related quality of life (HRQoL estimates exist for ME/CFS patients. The main purpose of this study was to estimate HRQoL scores using the EQ-5D-3L with Danish time trade-off tariffs. Secondary, the aims were to explore whether the results are not influenced by other conditions using regression, to compare the estimates to 20 other conditions and finally to present ME/CFS patient characteristics for use in clinical practice.All members of the Danish ME/CFS Patient Association in 2013 (n=319 were asked to fill out a questionnaire including the EQ-5D-3L. From these, 105 ME/CFS patients were identified and gave valid responses. Unadjusted EQ-5D-3L means were calculated and compared to the population mean as well as to the mean of 20 other conditions. Furthermore, adjusted estimates were calculated using ordinary least squares (OLS regression, adjusting for gender, age, education, and co-morbidity of 18 self-reported conditions. Data from the North Denmark Health Profile 2010 was used as population reference in the regression analysis (n=23,392.The unadjusted EQ-5D-3L mean of ME/CFS was 0.47 [0.41-0.53] compared to a population mean of 0.85 [0.84-0.86]. The OLS regression estimated a disutility of -0.29 [-0.21;-0.34] for ME/CFS patients in this study. The characteristics of ME/CFS patients are different from the population with respect to gender, relationship, employment etc.The EQ-5D-3L-based HRQoL of ME/CFS is significantly lower than the population mean and the lowest of all the compared conditions. The adjusted analysis confirms that poor HRQoL of ME/CFS is distinctly different from and not a proxy of the other included conditions. However, further studies are needed to exclude the possible selection bias of the current study.

1. PROBABILISTIC METHODOLOGY OF LOW CYCLE FATIGUE ANALYSIS

Institute of Scientific and Technical Information of China (English)

Jin Hui; Wang Jinnuo; Wang Libin

2003-01-01

The cyclic stress-strain responses (CSSR), Neuber's rule (NR) and cyclic strain-life relation (CSLR) are treated as probabilistic curves in local stress and strain method of low cycle fatigue analy sis. The randomness of loading and the theory of fatigue damage accumulation (TOFDA) are consid ered. The probabilistic analysis of local stress, local strain and fatigue life are constructed based on the first-order Taylor's series expansions. Through this method proposed fatigue reliability analysis can be accomplished.

2. Fatigue life and cyclic deformation behaviour of quenched and tempered steel AISI 4140 at two-step stress- and total-strain-controlled push-pull loading

Energy Technology Data Exchange (ETDEWEB)

Schulze, V.; Lang, K.H.; Macherauch, E. [Inst. fuer Werkstoffkunde I, Univ. Karlsruhe (Germany)

2003-05-01

The behaviour of steels at multi-step cyclic loading was explored up to now almost exclusively in fatigue-life-oriented investigations. Thus, only few works exist dealing with the cyclic deformation behaviour at two- and multi-step loading. Therefore, the cyclic deformation behaviour at two-step experiments with a single amplitude change (2-block experiments) and with multiple changes between two blocks of certain length and different amplitudes (multi-block experiments) was investigated in this work at the technically important steel AISI 4140 (German grade 42CrMo4). (orig.)

3. Fatigue Strength of Weathering Steel

Directory of Open Access Journals (Sweden)

Ludvík KUNZ

2012-03-01

Full Text Available Fatigue behaviour of Atmofix 52 steel (comparable to COR-TENâ steel exposed to atmospheric corrosion for 20 years was investigated. S-N curves for load symmetrical cycling and cycling with stress ratio R = 0 were determined on specimens detracted from a failed transmission tower. The data were compared with those on material without a rust layer. The fracture surfaces and, in particular, the sites of fatigue crack initiation were analyzed. Substantial decrease of fatigue life and fatigue limit due to corrosion exposition was found. Based on observation of surface layer with corrosion products and on fractographic analysis of failed specimens conclusions on fatigue damage mechanism were drawn. No grain boundary corrosion, which can be responsible for fatigue crack initiation, was observed. Initiation of fatigue cracks was related to surface roughness and took place exclusively on corrosion dimples.DOI: http://dx.doi.org/10.5755/j01.ms.18.1.1335

4. Geographic Distribution of VA Expenditures Report (GDX)

Data.gov (United States)

Department of Veterans Affairs — Geographic Distribution of VA Expenditures Report (GDX) located on the Expenditures page in the Expenditure Tables category. This report details VA expenditures at...

5. The impact of population ageing on future Danish drug expenditure

DEFF Research Database (Denmark)

Kildemoes, Helle Wallach

Background Population ageing is likely to place an increasing burden on future health care budgets. Several studies have demonstrated that the impact of ageing on future hospital expenditures will be overestimated when not accounting for proximity to death. This is because greater health care...... expenditure among the elderly partly is due the high "costs of dying". Aims The aim of this study was to estimate the impact of the ageing Danish population on future total expenditures on out-of-hospital prescription drugs and to describe the association between age and drug expenditure among survivors...... compared to that of decedents. Methods Taking expenditure during the last year of life and the changes in mortality rates into account, future drug expenditure was projected by multiplying estimated mean annual drug expenditure according to age, gender and survival status by the predicted future number...

6. The influence of hydrogen on the fatigue life of metallic leaf spring components in a vacuum environment

NARCIS (Netherlands)

Kouters, M.H.M.; Slot, H.M.; Zwieten, W. van; Veer, J. van der

2014-01-01

Hydrogen is used as a process gas in vacuum environments for semiconductor manufacturing equipment. If hydrogen dissolves in metallic components during operation it can result in hydrogen embrittlement. In order to assess if hydrogen embrittlement occurs in such a vacuum environment a special fatigu

7. Adults living with heart failure and fatigue

DEFF Research Database (Denmark)

Schjødt, Inge; Sommer, Irene; Bjerrum, Merete

Background Fatigue is one of the most common symptoms reported by patients with heart failure (HF). Fatigue negatively impacts on patients’ everyday life, prognosis and quality of life. No specific cure or effective interventions to alleviate fatigue are available. Over the past decade, qualitative...... To synthesise the best available evidence related to the lived experiences and management of fatigue in everyday life in adult patients with stable heart failure to develop effective interventions to support self-care. Specific questions on the patients’ lived experiences included: • How do patients with HF...... describe their experiences of fatigue? • How do patients with HF perceive the impact of fatigue in everyday life? • How do patients with HF manage fatigue and its consequences in everyday life? Methods A systematic literature search for published and unpublished studies 1995-2012 was carried out from...

8. Fatigue Life Prediction of Structural Details of Submarine Pressure Hull%耐压船体结构典型接点疲劳寿命评估

Institute of Scientific and Technical Information of China (English)

万正权; 王永军; 卞如冈; 朱邦俊

2004-01-01

The low-cycle fatigue induced crack propagation occurs in the structural details of submarine pressure hull when the applied stresses are superimposed on the residual welding stresses during its ascending and/or descending. It is important to assess the fatigue life for submarine pressure hull made of the high strength steel because the high strength steel presents a decrease in the material plasticity and fracture toughness with an increase of the tensile strength. In the present paper, a simplified approach is presented for low-cycle fatigue life prediction of submarine pressure hull based on the fracture mechanics and Paris law. The initial and critical sizes of cracks are proposed based on the statistics of the crack detection probability by non-destructive inspections and analysis results of the limit stress level of cracked cylindrical shell. The present method is employed to predict the fatigue life of a submarine pressure hull and experimental niodel of pressure conecylinder shell.The examples show that the results by the present method are in agreement with the experimental data of cone-cylinder model under cyclic external pressure.%潜艇在潜浮过程中,由于静水外压引起的工作应力与焊接残余应力叠加,形成拉压循环应力,导致耐压船体的局部结构可能出现低周疲劳裂纹.一般情况下,高强度钢在抗拉强度提高的同时往往伴随着材料塑性储备和断裂韧性的下降,因此分析高强度钢潜艇结构的低周疲劳寿命非常重要.本文基于断裂力学和Paris公式建立了潜艇耐压结构低周疲劳寿命的工程估算方法,根据裂纹无损检测的概率统计和含裂纹圆柱壳极限应力分析,给出了初始裂纹和裂纹临界状态的建议值.应用本文的简化方法分析了某潜艇结构和锥柱结合壳模型的低周疲劳寿命,锥柱结合壳模型的数值算例表明本文的计算结果与试验测试结果相吻合.

9. Study on Drill String Fatigue Life in Deepwater Drilling%深水钻井钻柱疲劳寿命研究

Institute of Scientific and Technical Information of China (English)

王佳佳; 陈建民

2016-01-01

Dynamic response of the deepwater drilling platform increases alternating loads of the drilling string�As a consequence, the calculation of drill string fatigue life becomes more complicated�By using the numeri⁃cal simulation method, a method for studying drill string fatigue life is proposed based on AQWA module, transi⁃ent dynamic analysis module and fatigue analysis module of Ansys⁃Workbench�A case study was conducted to ob⁃tain motion response of some marine platform and further get the drill string fatigue life of about 102�61 d�Calculation results show that the drill string serving up to 100 days must have flaw detection to determine whether it can continue to run in the deepwater drilling operation up to 1 000 m�In particular, great attention should be paid to the drilling string near the surface.%深水钻井作业中平台的动力响应将使钻柱承受更多的交变载荷，钻柱疲劳寿命的计算过程更为复杂。应用数值模拟方法，通过Ansys⁃Workbench中的AQWA模块、瞬态动力学分析模块以及疲劳分析模块，提出了一种研究深水钻井中钻柱疲劳寿命问题的方法。通过实例计算，得到了某海洋环境下平台的运动响应，进而得到钻柱的疲劳极限寿命约102�61 d。计算结果表明，对于水深1000 m的深水钻井作业，服役时间达到100 d的钻柱必须经过探伤检测，方能确定是否继续使用，且尤其应注意靠近水面部分的钻柱。

10. Catastrophic Medical Expenditure Risk

NARCIS (Netherlands)

G. Flores (Gabriela); O.A. O'Donnell (Owen)

2012-01-01

textabstractMedical expenditure risk can pose a major threat to living standards. We derive decomposable measures of catastrophic medical expenditure risk from reference-dependent utility with loss aversion. We propose a quantile regression based method of estimating risk exposure from cross-section

11. Catastrophic Medical Expenditure Risk

NARCIS (Netherlands)

G. Flores (Gabriela); O.A. O'Donnell (Owen)

2012-01-01

textabstractMedical expenditure risk can pose a major threat to living standards. We derive decomposable measures of catastrophic medical expenditure risk from reference-dependent utility with loss aversion. We propose a quantile regression based method of estimating risk exposure from cross-section

12. Optimization design of joint under fatigue life%疲劳寿命下连接件的优化设计

Institute of Scientific and Technical Information of China (English)

姜昊; 姜金辉; 沈雨晨

2015-01-01

连接件是飞机结构中常见的承载结构，但也是常见的疲劳源，连接件上紧固件钉传载荷和孔边旁路载荷直接影响疲劳寿命，采用bush元、beam元和rbar模拟紧固件和板的连接关系，建立了连接件细节有限元模型。为降低端部孔的应力集中，使连接板的厚度呈台阶形状，计算紧固件载荷的分布，然后通过应力严重系数法，确定各个连接件结构的严重孔，最后对各个严重孔的疲劳寿命进行了对比，计算结果表明与理论相符，对结构的优化设计具有参考价值。%The joint is the common bearing structure in the aircraft ,but it’s also a common source of fatigue .The pin load on the fasteners and the bypass load on the side of hole directly affect the fatigue life .The fasteners and plate con‐nection relationship simulated by the bush element ,beam element and rbar element in the article .Established the joint detail finite element model .thickness of connecting plate shape steps ,Which can reduce the stress concentration of the end hole .And calculate the load distribution .Then determine the serious hole in the various joints ,by Stress Severity Factor approach .Finally the fatigue life of various serious holes were compared ,the calculation results show that accords with the theory ,the optimization of structure design has reference value .

13. Casting dimensional control and fatigue life prediction for permanent mold casting dies. Technical progress report, September 29, 1993-- September 30, 1994

Energy Technology Data Exchange (ETDEWEB)

NONE

1994-11-01

First year efforts as part of a three year program to address metal casting dimensional control and fatigue life prediction for permanent mold casting dies are described. Procedures have been developed and implemented to collect dimensional variability data from production steel castings. The influence of process variation and casting geometry variables on dimensional tolerances have been investigated. Preliminary results have shown that these factors have a significant influence on dimensional variability, although this variability is considerably less than the variability indicated in current tolerance standards. Gage repeatability and reproducibility testing must precede dimensional studies to insure that measurement system errors are acceptably small. Also initial efforts leading to the development and validation of a CAD/CAE model to predict the thermal fatigue life of permanent molds for aluminum castings are described. An appropriate thermomechanical property database for metal, mold and coating materials has been constructed. A finite element model has been developed to simulate the mold temperature distribution during repeated casting cycles. Initial validation trials have indicated the validity of the temperature distribution model developed.

14. Electronic visual analogue scales for pain, fatigue, anxiety and quality of life in people with multiple sclerosis using smartphone and tablet: a reliability and feasibility study.

Science.gov (United States)

Kos, D; Raeymaekers, J; Van Remoortel, A; D'hooghe, M B; Nagels, G; D'Haeseleer, M; Peeters, E; Dams, T; Peeters, T

2017-09-01

To explore the reliability and feasibility of electronic visual analogue scales in people with multiple sclerosis (MS) and healthy individuals. Cross-sectional observational study Setting: Clinical setting Subjects: Convenience sample of 52 people with MS and 52 matched healthy controls Interventions: NA Main measures: Participants scored 15 statements assessing fatigue, pain, anxiety and quality of life on an electronic visual analogue scale (eVAS), either using a smartphone or a tablet (randomly allocated). To check for test-retest reliability, statements were administered in two separate randomly ordered groups. Subjects completed a feasibility questionnaire. Mean (SD) eVAS scores ranged from 35 (28.1) to 80 (22.1) in MS group, and from 57 (28.0) to 86 (13.2) in controls. Intra Class Correlations ranged from 0.73 to 0.95 in MS sample; 0.61 to 0.92 in controls. For most statements, Bland-Altman plots indicated no systematic error, but relatively large random error of the eVAS scores (exceeding 20mm). Considerable ceiling effects (i.e. better health) were found in healthy controls. Similar reliability was found among smartphone or tablet, different demographic groups and the experience-groups. Electronic visual analogue scales are reliable and useful for people with MS to register fatigue, pain, anxiety and quality of life.

Institute of Scientific and Technical Information of China (English)

李静; 孙强; 李春旺; 张忠平; 乔艳江

2011-01-01

Based on the critical plane approach,the recently proposed multiaxial fatigue life prediction model applied to the smoothing tubular specimen is extended to assess the multiaxial fatigue life of notched one. Besides,with the aid of finite element analysis (FEA),the orientation of the critical plane and the effective cyclic parameter are determined by using the coordinate transformation principle. In the meantime,the proposed model is modified to take into consideration of the effect of mean stress when existing the mean stress.%基于临界平面法,在分析光滑薄壁圆管试件疲劳寿命预测模型的基础上,借助有限元应力应变分析,进一步将模型推广应用到了缺口试件的多轴疲劳寿命预测中,并利用坐标变换原理,明确了临界平面及有效循环变量的确定方法.在存在平均应力的情况下,分析了平均应力对疲劳寿命的影响,并对所建模型进行了平均应力修正.

16. Predictors of health-related quality of life and fatigue in systemic sclerosis: evaluation of the EuroQol-5D and FACIT-F assessment tools.

Science.gov (United States)

Strickland, Gemma; Pauling, John; Cavill, Charlotte; McHugh, Neil

2012-08-01

This study evaluates predictors of health-related quality of life (HRQoL) and fatigue in systemic sclerosis (SSc) using two novel self-report indices. A cross-sectional study of patients with SSc was undertaken using a postal questionnaire including the EuroQol-5Domain health questionnaire (EQ-5D™), Functional Assessment of Chronic Illness Therapy-Fatigue scale (FACIT-F) and the Scleroderma Health Assessment Questionnaire (SHAQ). The EQ-5D assesses five domains of health quality and is quantified as a time trade-off (TTO) value and patient global assessment (0-100 visual analogue scale [VAS]). The FACIT-F is a 13-item questionnaire (0-52 scale). Higher scores for both the EQ-5D and FACIT-F indicate better health. Case notes were scrutinised for patient demographics, disease duration, serology and clinical phenotype. Sixty-eight patients (60 females, mean age 62.6 years) completed the questionnaires. Fatigue correlated closely with HRQoL (r (s) = 0.78 and 0.77 for FACIT-F vs. EQ-5D VAS and TTO respectively, p < 0.01) and disability (r (s) = -0.74 for FACIT-F vs. HAQ-DI, p < 0.01). Pain was the most frequently reported health problem (80 %) in the EQ-5D. HRQoL also correlated closely with disability (r (s) = 0.83 for EQ-5D vs. HAQ-DI, p < 0.01). SHAQ-VAS scores correlated well with the FACIT-F, EQ-5D and HAQ-DI scores (p < 0.05 for all comparisons). Of the patient demographics and clinical disease associations, only the absence of upper gastrointestinal complications was associated with better levels of fatigue, HRQoL and function. There is a strong correlation between disability, fatigue and HRQoL measured using self-reports, possibly reflecting similarly perceived health beliefs amongst patients across outcomes. There was little association between self-report indices and patient demographics and/or clinical phenotype.

17. Monitoring microstructural evolution of alloy 617 with non-linear acoustics for remaining useful life prediction; multiaxial creep-fatigue and creep-ratcheting

Energy Technology Data Exchange (ETDEWEB)

Lissenden, Cliff [Pennsylvania State Univ., State College, PA (United States); Hassan, Tasnin [North Carolina State Univ., Raleigh, NC (United States); Rangari, Vijaya [Tuskegee Univ., Tuskegee, AL (United States)

2014-10-30

The research built upon a prior investigation to develop a unified constitutive model for design-­by-­analysis of the intermediate heat exchanger (IHX) for a very high temperature reactor (VHTR) design of next generation nuclear plants (NGNPs). Model development requires a set of failure data from complex mechanical experiments to characterize the material behavior. Therefore uniaxial and multiaxial creep-­fatigue and creep-­ratcheting tests were conducted on the nickel-­base Alloy 617 at 850 and 950°C. The time dependence of material behavior, and the interaction of time dependent behavior (e.g., creep) with ratcheting, which is an increase in the cyclic mean strain under load-­controlled cycling, are major concerns for NGNP design. This research project aimed at characterizing the microstructure evolution mechanisms activated in Alloy 617 by mechanical loading and dwell times at elevated temperature. The acoustic harmonic generation method was researched for microstructural characterization. It is a nonlinear acoustics method with excellent potential for nondestructive evaluation, and even online continuous monitoring once high temperature sensors become available. It is unique because it has the ability to quantitatively characterize microstructural features well before macroscale defects (e.g., cracks) form. The nonlinear acoustics beta parameter was shown to correlate with microstructural evolution using a systematic approach to handle the complexity of multiaxial creep-­fatigue and creep-­ratcheting deformation. Mechanical testing was conducted to provide a full spectrum of data for: thermal aging, tensile creep, uniaxial fatigue, uniaxial creep-­fatigue, uniaxial creep-ratcheting, multiaxial creep-fatigue, and multiaxial creep-­ratcheting. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and Optical Microscopy were conducted to correlate the beta parameter with individual microstructure mechanisms. We researched

18. Iyengar-Yoga Compared to Exercise as a Therapeutic Intervention during (Neoadjuvant Therapy in Women with Stage I–III Breast Cancer: Health-Related Quality of Life, Mindfulness, Spirituality, Life Satisfaction, and Cancer-Related Fatigue

Directory of Open Access Journals (Sweden)

Désirée Lötzke

2016-01-01

Full Text Available This study aims to test the effects of yoga on health-related quality of life, life satisfaction, cancer-related fatigue, mindfulness, and spirituality compared to conventional therapeutic exercises during (neoadjuvant cytotoxic and endocrine therapy in women with breast cancer. In a randomized controlled trial 92 women with breast cancer undergoing oncological treatment were randomly enrolled for a yoga intervention (YI (n=45 or for a physical exercise intervention (PEI (n=47. Measurements were obtained before (t0 and after the intervention (t1 as well as 3 months after finishing intervention (t2 using standardized questionnaires. Life satisfaction and fatigue improved under PEI (p<0.05 but not under YI (t0 to t2. Regarding quality of life (EORTC QLQ-C30 a direct effect (t0 to t1; p<0.001 of YI was found on role and emotional functioning, while under PEI only emotional functioning improved. Significant improvements (p<0.001 were observed at both t1 and t2 also for symptom scales in both groups: dyspnea, appetite loss, constipation, and diarrhea. There was no significant difference between therapies for none of the analyzed variables neither for t1 nor for t2. During chemotherapy, yoga was not seen as more helpful than conventional therapeutic exercises. This does not argue against its use in the recovery phase.

19. 钢质蜂窝夹芯梁高温疲劳试验及寿命预测研究%Investigation on the fatigue behaviors and life prediction of steel honeycomb sandwich beams

Institute of Scientific and Technical Information of China (English)

芦颉; 邹广平; 曹扬; 唱忠良; 刘宝君

2011-01-01

针对实际工程中钢质蜂窝夹芯结构在热环境下的疲劳耐久性及寿命问题,开展了400℃下的三点弯曲疲劳试验研究,得到S-N曲线.基于刚度退化,提出一种用于该类材料在高温下的疲劳寿命预测模型和损伤演化模型.该方法允许预测不同载荷水平下的疲劳寿命,避免了大量重复性疲劳试验.应用于模型的参数与材料性质、高温等试验条件有关.借助简单模型,完成了钢质蜂窝梁高温寿命预测及损伤演化预测,预测值与试验值吻合较好.%In the industrial field, an investigation on how temperature can affect damage and fatigue life of a honeycomb sandwich structure is significant. The aim of this work is to investigate fatigue behaviors of the steel honeycomb sandwich beams at 400℃ by three-point bending fatigue experiments. An S-N curve was obtained. Based on stiffness degradation, life prediction and damage evolution models were developed. This approach allowed the prediction of fatigue life under different load levels while avoiding a large number of repetitive fatigue tests. Parameters used in the model depended on the material properties and high temperature test conditions among other things. The developed models were applied to analyze the fatigue life and damage evolution of steel honeycomb sandwich specimens under fatigue. The results show that experimental and prediction results were in good agreement. Thus the proposed method is feasible.

20. The fatigue life analysis and optimization of landing gear for a large amphibian aircraft%大型水陆两栖飞机起落架疲劳寿命分析与优化

Institute of Scientific and Technical Information of China (English)

姜成杰; 许锋

2015-01-01

以疲劳寿命分析理论成果为指导，对大型水陆两栖飞机主起落架进行疲劳寿命计算分析与结构优化研究。通过Hypermesh进行模型有限元前处理，在NASTRAN中计算应力分布结果，利用NcodeDesignlife研究起落架整体结构件疲劳寿命；通过LMS Virtual．Lab建立前起落架刚柔耦合模型，得到各个零部件连接部位节点力，从而完成对各个零部件的独立建模分析计算；基于疲劳寿命的结构优化技术，以Optistruct为工具对起落架疲劳寿命薄弱部位进行形状优化，使得疲劳寿命进一步提高。%Based on the theory of fatigue life analysis , it describes the fatigue life analysis and optimization of the main landing gear for a large amphibian aircraft .It builds the landing gear element model in Hypermesh , calcu-lates the distribution in NASTRAN , analyzes the landing gear overall structure fatigue life in NcodeDesignlife .It establishes the rigid flexible coupling model of the main landing gear and obtains the node forces of all connected parts through LMS Virtual .Lab, sets up the models one by one for each parts to obtain the more accurate fatigue life of each parts.At last, based on the fatigue life structure optimization technology , it realizes the shape optimi-zation for the positions of the main landing gear with little fatigue life to make further improvement in Optistruct .

1. Fatigue life extension of epoxy materials using ultrafast epoxy-SbF5 healing system introduced by manual infiltration

Directory of Open Access Journals (Sweden)

X. J. Ye

2015-03-01

Full Text Available The present paper is devoted to the verification of the capability of epoxy-SbF5 system as a healing chemistry for rapidly retarding and/or arresting fatigue cracks in epoxy materials at room temperature. Owing to the very fast curing speed of epoxy catalyzed by SbF5, epoxy monomer and the hardener (ethanol solution of SbF5–ethanol complex are successively infiltrated into the fracture plane under cyclic loading during the tension-tension fatigue test. As a result, the mechanisms including hydrodynamic pressure crack tip shielding, polymeric wedge and adhesive bonding of the healing agent are revealed. It is found that the healing agent forms solidified wedge at the crack tip within 20 s after start of polymerization of the epoxy monomer, so that the highest healing effect is offered at the moment. The epoxy-SbF5 system proves to be effective in rapidly obstructing fatigue crack propagation (despite that its cured version has lower fracture toughness than the matrix, and satisfies the requirement of constructing fast self-healing polymeric materials.

2. Modafinil May Alleviate Poststroke Fatigue

DEFF Research Database (Denmark)

Poulsen, Mai Bang; Damgaard, Bodil; Zerahn, Bo

2015-01-01

BACKGROUND AND PURPOSE: Poststroke fatigue is common and reduces quality of life. Current evidence for intervention is limited, and this is the first placebo-controlled trial to investigate treatment of poststroke fatigue with the wakefulness promoting drug modafinil. METHODS: The trial was rando......: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01800097....

3. The effect of SiC powder mixing electrical discharge machining on white layer thickness, heat flux and fatigue life of AISI D2 die steel

Directory of Open Access Journals (Sweden)

Ahmed Al-Khazraji

2016-09-01

Full Text Available This paper deals with studying the effect of powder mixing electrical discharge machining (PMEDM parameters using copper and graphite electrodes on the white layer thickness (WLT, the total heat flux generated and the fatigue life. Response surface methodology (RSM was used to plan and design the experimental work matrices for two groups of experiments: for the first EDM group, kerosene dielectric was used alone, whereas the second was treated by adding the SiC micro powders mixing to dielectric fluid (PMEDM. The total heat flux generated and fatigue lives after EDM and PMEDM models were developed by FEM using ANSYS 15.0 software. The graphite electrodes gave a total heat flux higher than copper electrodes by 82.4%, while using the SiC powder and graphite electrodes gave a higher total heat flux than copper electrodes by 91.5%. The lowest WLT values of 5.0 µm and 5.57 µm are reached at a high current and low current with low pulse on time using the copper and graphite electrodes and the SiC powder, respectively. This means that there is an improvement in WLT by 134% and 110%, respectively, when compared with the use of same electrodes and kerosene dielectric alone. The graphite electrodes with PMEDM and SiC powder improved the experimental fatigue safety factor by 7.30% compared with the use of copper electrodes and by 14.61% and 18.61% compared with results using the kerosene dielectric alone with copper and graphite electrodes, respectively.

4. Health-Related Quality of Life Among Chinese Patients With Rheumatoid Arthritis: The Predictive Roles of Fatigue, Functional Disability, Self-Efficacy, and Social Support.

Science.gov (United States)

Gong, Guilan; Mao, Jing

2016-01-01

Health-related quality of life (HRQoL) is an important outcome measure in chronic diseases like rheumatoid arthritis (RA). However, there is a paucity of literature from mainland China on HRQoL and factors that influence it in people with RA. The aim of this study was to assess HRQoL and to determine which factors, based on the Wilson and Cleary model, contribute to the prediction of HRQoL among persons with RA in mainland China. A cross-sectional design was used. Persons with RA (N = 207) were recruited from the outpatient clinics of a university-affiliated hospital in central China. Participants responded to a demographic data questionnaire, the Medical Outcomes Study 36-Item Short Form Health Survey (SF-36), the Multidimensional Fatigue Inventory, the Health Assessment Questionnaire-Disability Index, the eight-item Arthritis Self-Efficacy Scale, and the Medical Outcomes Study Social Support Survey. Structural equation modeling was used to estimate the effects of factors from the Wilson and Cleary model on HRQoL. Scores on all SF-36 subscales were significantly lower in patients with RA compared with a general Chinese sample. Lower self-efficacy, greater fatigue, greater functional disability, lower social support, being unemployed, higher disease activity, more comorbidities, lower income level, being female, living in rural settings, and being older were directly or indirectly significantly and negatively associated with HRQoL; 67% of the total variance of HRQoL scores was explained. Patients with RA in mainland China experience impaired physical and mental health. Targeted and culturally sensitive interventions should be strengthened to improve the HRQoL of this population. Essentials in improving the HRQoL are enhancing self-efficacy, relieving fatigue, delaying the onset of disabilities, increasing social support, and controlling disease activity.

5. Motor, Psychiatric and Fatigue Features Associated with Nutritional Status and Its Effects on Quality of Life in Parkinson’s Disease Patients

Science.gov (United States)

2014-01-01

Objectives Parkinson’s disease (PD) patients are more likely to develop impaired nutritional status because of the symptoms, medications and complications of the disease. However, little is known about the determinants and consequences of malnutrition in PD. This study aimed to investigate the association of motor, psychiatric and fatigue features with nutritional status as well as the effects of malnutrition on different aspects of quality of life (QoL) in PD patients. Methods One hundred and fifty patients with idiopathic PD (IPD) were recruited in this study. A demographic checklist, the Unified Parkinson’s Disease Rating Scale (UPDRS), the Hospital Anxiety and Depression Scale (HADS) and the Fatigue Severity Scale (FSS) were completed through face-to-face interviews and clinical examinations. The health-related QoL (HRQoL) was also evaluated by means of the Parkinson’s Disease Questionnaire (PDQ-39). For evaluation of nutritional status, the Mini Nutritional Assessment (MNA) questionnaire was applied together with anthropometric measurements. Results Thirty seven (25.3%) patients were at risk of malnutrition and another 3 (2.1%) were malnourished. The total score of the UPDRS scale (r = −0.613, Pnutritional status [2.5 vs. 2.0; Pnutritional status. Except for stigma, all other domains of the PDQ-39 were significantly correlated with the total score of the MNA. Conclusion Our study demonstrates that disease duration, severity of motor and psychiatric symptoms (depression, anxiety) and fatigue are associated with nutritional status in PD. Different aspects of the HRQoL were affected by patients’ nutritional status especially the emotional well-being and mobility domains. PMID:24608130

6. Comparison between the C-leg microprocessor-controlled prosthetic knee and non-microprocessor control prosthetic knees: a preliminary study of energy expenditure, obstacle course performance, and quality of life survey.

Science.gov (United States)

Seymour, Ron; Engbretson, Brenda; Kott, Karen; Ordway, Nathaniel; Brooks, Gary; Crannell, Jessica; Hickernell, Elise; Wheeler, Katie

2007-03-01

This study investigated energy expenditure and obstacle course negotiation between the C-leg and various non-microprocessor control (NMC) prosthetic knees and compared a quality of life survey (SF-36v2) of use of the C-leg to national norms. Thirteen subjects with unilateral limb loss (12 with trans-femoral and one with a knee disarticulation amputation) participated in the study. The mean age was 46 years, range 30-75. Energy expenditure using both the NMC and C-leg prostheses was measured at self-selected typical and fast walking paces on a motorized treadmill. Subjects were also asked to walk through a standardized walking obstacle course carrying a 4.5 kg (10 lb) basket and with hands free. Finally, the SF-36v2 was completed for subjects while using the C-leg. Statistically significant differences were found in oxygen consumption between prostheses at both typical and fast paces with the C-leg showing decreased values. Use of the C-leg resulted in a statistically significant decrease in the number of steps and time to complete the obstacle course. Scores on a quality of life index for subjects using the C-leg were above the mean for norms for limitation in the use of an arm or leg, equal to the mean for the general United States population for the physical component score and were above this mean for the mental component score. Based on oxygen consumption and obstacle course findings, the C-leg when compared to the NMC prostheses may provide increased functional mobility and ease of performance in the home and community environment. Questionnaire results suggest a minimal quality of life impairment when using a C-leg for this cohort of individuals with amputation.

7. Increasing Public Expenditure

National Research Council Canada - National Science Library

Ammar Ben Zaed

2015-01-01

This article aims to analyze and interpret the phenomenon of increased public expenditures and test explanatory theories as well as to analyze Abstract the relationship between public spending and GDP...

Institute of Scientific and Technical Information of China (English)

包名; 尚德广; 陈宏

2012-01-01

According to the concept of critical plane, a fatigue life prediction method is presented under random multiaxial loading. Firstly, a multiaxial cycle counting method is proposed based on the von Mises equivalent strain and equivalent stress concept, sign correctional formula and traditional uniaxial rainflow cycle counting method. This method mainly aimed at solving the problem of ' sign lost' in von Mises equivalent strain and equivalent stress history under multiaxial random loading, suggesting adopt a sign formula correct it, then cycle count the von Mises equivalent strain history with a traditional uniaxial cycle counting method, which can not only be convenient for evaluating the damage of succeeding procedure, but make the uniaxial cycle counting method successfully apply in multiaxial load-time history. After that, the normal and shear strains are analyzed for cycle-counted equivalent strain cycles, and the critical plane as well as fatigue damage parameters are also defined for these cycles. Finally, combining several familiar multiaxial fatigue damage models, Miner's linear rule together with uniaxial fatigue data of Enl5R steel, predicting its fatigue life under random axial-torsional loading, and the results show that the life predictions agree well with experimental results.%提出一种多轴随机载荷下的疲劳寿命预测方法.该法首先基于von Mises等效应变和等效应力概念、符号修正公式以及传统的单轴雨流计数法,提出一种多轴随机载荷下的循环计数方法.此法主要针对多轴随机载荷下vonMises等效应变和等效应力历程中的符号丢失问题,建议采用一种符号公式来加以修正,以便于结合单轴雨流计数法对修正后的von Mises等效应变历程进行较为精准地循环计数,从而不仅有利后续疲劳损伤的正确估算,还可使单轴循环计数法能有效地应用于多轴载荷—时间历程.然后分析von Mises等效应变循环内的应变状态,

9. Driver Fatigue Features Extraction

Directory of Open Access Journals (Sweden)

Gengtian Niu

2014-01-01

Full Text Available Driver fatigue is the main cause of traffic accidents. How to extract the effective features of fatigue is important for recognition accuracy and traffic safety. To solve the problem, this paper proposes a new method of driver fatigue features extraction based on the facial image sequence. In this method, first, each facial image in the sequence is divided into nonoverlapping blocks of the same size, and Gabor wavelets are employed to extract multiscale and multiorientation features. Then the mean value and standard deviation of each block’s features are calculated, respectively. Considering the facial performance of human fatigue is a dynamic process that developed over time, each block’s features are analyzed in the sequence. Finally, Adaboost algorithm is applied to select the most discriminating fatigue features. The proposed method was tested on a self-built database which includes a wide range of human subjects of different genders, poses, and illuminations in real-life fatigue conditions. Experimental results show the effectiveness of the proposed method.

10. Simulation of Stochastic Loads for Fatigue Experiments

DEFF Research Database (Denmark)

Sørensen, John Dalsgaard; Brincker, Rune

A simple direct simulation method for stochastic fatigue load generation is described in this paper. The simulation method is based on the assumption that only the peaks of the load process significantly affect the fatigue life. The method requires the conditional distribution functions of load...... second using an IBM PC. Finally the proposed simulation method for fatigue load generation is tested by comparing some fatigue damage measures obtained by the simulation methods....

11. Energy Expenditure and Intake Methods

NARCIS (Netherlands)

Westerterp, K.R.

2015-01-01

The main components of total energy expenditure are energy expenditure for maintenance or basal metabolic rate, the thermic effect of food or diet-induced energy expenditure (DEE), and the energy cost of physical activity or activity-induced energy expenditure (AEE). This chapter describes methods t

12. Fatigue life evaluation of a cracked pipeline pipe operating under variable; Estudo da vida em fadiga com variacao de pressao interna em tubos com defeitos

Energy Technology Data Exchange (ETDEWEB)

Betanzos, J.; Mattei, F. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil); Strohaecker, T. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Programa de Pos-graduacao em Engenharia de Minas, Metalurgia e Materiais; Marinho, R.; Hoppe, R.; Donato, G. [PETROBRAS, Rio de Janeiro, RJ (Brazil)

2005-07-01

Fatigue cracks in welded joints are commonly found in gas and oil pipelines and usually pumping is interrupted for repair. The strength of welded joints with defects, and consequently, the useful life of a pipeline, is an important information that could lead to great improvements in the reliability. To evaluate the working conditions determined by standards, specimens with 22'' diameter and 1/2'' wall thickness API 5L X60 pipes were used. Two semi-elliptical cracks were electro spark machined, with 50% and 25% of the tube wall thickness depths and a length/depth ratio of 1/20. Both defects were located in the HAZ of the tube longitudinal seam weld. Applying a cyclic internal pressure it was possible to propagate a fatigue crack until a through-thickness condition. The results show that the pressures to initiate crack propagation are too much higher than the pressures allowed by the standards for this kind of defect. (author)

13. Fatigue life prediction using multiaxial energy calculations with the mean stress effect to predict failure of linear and nonlinear elastic solids

Science.gov (United States)

Nagode, Marko; Šeruga, Domen

An approach is presented that enables the calculation of elastic strain energy in linear and nonlinear elastic solids during arbitrary thermomechanical load cycles. The approach uses the simple fact that the variation of both strain and complementary energies always forms a rectangular shape in stress-strain space, hence integration is no longer required to calculate the energy. Furthermore, the approach considers the mean stress effect so that predictions of fatigue damage are more realistically representative of real-life experimental observations. By doing so, a parameter has been proposed to adjust the mean stress effect. This parameter α is based on the well-known Smith-Watson-Topper energy criterion, but allows consideration of other arbitrary mean stress effects, e.g. the Bergmann type criterion. The approach has then been incorporated into a numerical method which can be applied to uniaxial and multiaxial, proportional and non-proportional loadings to predict fatigue damage. The end result of the method is the cyclic evolution of accumulated damage. Numerical examples show how the method presented in this paper could be applied to a nonlinear elastic material.

14. EVAPRED - A CODE FOR FATIGUE ANALYSIS OPTIMIZATION

Directory of Open Access Journals (Sweden)

Dorin LOZICI-BRÎNZEI

2010-03-01

Full Text Available The fatigue can be, in fact, defined as: “failure under a repeated or otherwise varying load, which never reaches a level sufficient to cause failure in a single application”.Physical testing is clearly unrealistic for every design component. In most applications, fatigue-safe life design requires the prediction of the component fatigue life that accounts for predicted service loads and materials. The primary tool for both understanding and being able to predict and avoid fatigue has proven to be the finite element analysis (FEA. Computer-aided engineering (CAE programs use three major methods to determine the total fatigue life: Stress life (SN, Strain life (EN and Fracture Mechanics (FM. FEA can predict stress concentration areas and can help design engineers to predict how long their designs are likely to last before experiencing the onset of fatigue.

15. Multiaxial Fatigue Life Prediction Based on Damage Mechanics and Critical Plane Method%基于损伤力学-临界面法预估多轴疲劳寿命

Institute of Scientific and Technical Information of China (English)

刘俭辉; 王生楠; 黄新春; 傅益战

2015-01-01

基于损伤力学理论建立的非线性疲劳寿命预估模型在多轴疲劳寿命预估中获得了广泛的应用，但该模型并未考虑损伤面发生的位置及其物理意义，将其与临界面法相结合提出一种新的多轴非线性疲劳寿命预估模型，新模型能够弥补现有的非线性疲劳寿命预估模型未考虑临界面物理意义的不足。新模型从损伤的角度来预估多轴疲劳寿命，不仅考虑了临界面上裂纹形成及扩展的物理意义、相位差对附加强化现象的影响，而且对非对称加载下的平均应变进行修正。新模型仅仅利用单轴疲劳试验数据以及单轴疲劳材料常数就可以预估出试样的多轴疲劳寿命，从而避免了代价高昂的多轴疲劳试验。采用45钢、316不锈钢、钛合金TC4三种材料的多轴疲劳试验数据对提出的模型进行评估和验证，对几种材料比例/非比例以及对称/非对称加载下的多轴疲劳寿命进行预估，预估结果与试验结果的误差都在5%以内，结果表明提出的多轴非线性疲劳寿命预估模型具有较高的预估精度。%The established nonlinear fatigue life prediction model based on the theory of damage mechanics has been widely applied to multiaxial fatigue life prediction. However, this model does not take into account the location of damage and its physical significance. A new multiaxial nonlinear fatigue life prediction model is put forward based on damage mechanics and critical plane method. The new model can make up the shortage of the existing nonlinear fatigue life prediction model, which did not consider the significance of critical plane. The new model predicts multiaxial fatigue life from the perspective of damage. It not only considers the physical significance of crack formation and propagation and the influence of the phase delay on additional strengthening phenomenon, but also revises the mean strain under asymmetrical loading. The new

16. Incompatibility and Mental Fatigue

Science.gov (United States)

Herzog, Thomas R.; Hayes, Lauren J.; Applin, Rebecca C.; Weatherly, Anna M.

2011-01-01

A straightforward prediction from attention restoration theory is that the level of incompatibility in a person's life should be positively correlated with that person's level of mental (or directed attention) fatigue. The authors tested this prediction by developing a new self-report measure of incompatibility in which they attempted to isolate…

17. Cumulative fatigue damage models

Science.gov (United States)

Mcgaw, Michael A.

1988-01-01

The problem of calculating expected component life under fatigue loading conditions is complicated by the fact that component loading histories contain, in many cases, cyclic loads of widely varying amplitudes. In such a case a cumulative damage model is required, in addition to a fatigue damage criterion, or life relationship, in order to compute the expected fatigue life. The traditional cumulative damage model used in design is the linear damage rule. This model, while being simple to use, can yield grossly unconservative results under certain loading conditions. Research at the NASA Lewis Research Center has led to the development of a nonlinear cumulative damage model, named the double damage curve approach (DDCA), that has greatly improved predictive capability. This model, which considers the life (or loading) level dependence of damage evolution, was applied successfully to two polycrystalline materials, 316 stainless steel and Haynes 188. The cumulative fatigue behavior of the PWA 1480 single-crystal material is currently being measured to determine the applicability of the DDCA for this material.

18. Low Cycle Fatigue Life Prediction of Metallic Materials under Multi-Axial Nonproportional Loading: An Overview%金属材料多轴非比例低周疲劳寿命预测概述

Institute of Scientific and Technical Information of China (English)

吴昊; 仲政

2016-01-01

工程中的大多数构件承受着比例或非比例多轴疲劳荷载作用,而非比例强化效应会大大影响其多轴疲劳寿命.精确预测金属材料在多轴非比例荷载下的低周疲劳寿命需要同时考虑等向强化、随动强化及非比例强化效应下的材料本构关系,并在临界面上计算出相应应力应变值,根据不同疲劳失效形式选取不同类型的失效模型来确定疲劳寿命.本文针对这一过程中重要知识点进行阐述,并介绍了相关模型与理论.%Many engineering components are subjected to multiaxial fatigue loading which can be proportional or non-proportional.The non-proportional hardening effect has a significant influence on multiaxial fatigue life.Accurate prediction of the low cycle fatigue life of metallic materials under multiaxial non-proportional loading should employ constitutive relations considering isotropic hardening,kinematic hardening and non-proportional hardening effects simultaneously.By calculating the corresponding stress and strain components on the critical plane,the fatigue life could be estimated with the help of different fatigue failure models.This paper gives an overview of the concepts concerning the fatigue life predictions,as well as the related models and theories.

19. Prediction on Rolling Contact Fatigue Crack Initiation Life of Rails%钢轨滚动接触疲劳裂纹萌生寿命预测*

Institute of Scientific and Technical Information of China (English)

邓铁松; 李伟; 温泽峰; 金学松

2013-01-01

A plain-strain finite element model of the rail was established by finite element software ABAQUS.The con-stitutive relation of 1070 steel was created by Jiang and Sehitoglu’s cyclic plastic constitutive model,and the repeatedly rolling of wheel on the rail was simulated by the moving load.The fatigue crack initiation life was calculated with Jiang’s fatigue model,and the effects of rail material defect (cavity)and friction coefficient on the fatigue crack initiation life were analyzed.The results show that,after the thirtieth pass,stress-strain response of the rail surface becomes stable.The maxi-mum residual stress and strain are located in the subsurface of the rail.The life of normal rail is 17~27 times longer than that of rail with defect (material cavity),and the position of crack initiation around the defect is located at 135°~150°. With the increasing of the friction coefficient,rolling contact fatigue crack initiation life of the rail is decreased,and its im-pacts on the expansion direction of crack and the position of crack are not significant.%利用有限元分析软件ABAQUS建立钢轨平面应变有限元模型，并利用Jiang-Sehitoglu循环塑性本构关系建立1070钢轨钢本构关系，通过移动载荷模拟车轮在钢轨上的反复滚动，并通过Jiang伤损模型计算疲劳裂纹萌生寿命，分析钢轨材料缺陷（空洞）和不同摩擦因数对疲劳裂纹萌生寿命的影响。计算结果表明，当车轮滚动30次时，钢轨表层的应力应变响应趋于稳定，最大残余应力应变发生在次表层，正常钢轨的萌生寿命是含材料缺陷（存在材料空洞）钢轨的17～27倍，且缺陷（材料空洞）处裂纹萌生位置为135°～150°位置，随着摩擦因数增大，钢轨滚动接触疲劳裂纹萌生寿命逐渐减小，对裂纹萌生方向和位置影响不大。

20. 涡轮叶片高温多轴低周疲劳/蠕变寿命研究%Research on low cycle-multiaxial fatigue-creep life prediction at high temperature for turbine blade

Institute of Scientific and Technical Information of China (English)

彭立强; 王健

2009-01-01

SHANG Deguang multiaxial fatigue damage model was used to amend Man-son-Coffin equation of multiaxial fatigue prediction and SWT(Smith-Waston-Topper) formu-la, based on working condition of turbine rotor blade in aviation engine. A new method of fa-tigue life prediction of turbine blade was presented, which was adapted for non-proportional loading of turbine blade fatigue damage at high temperature. A case of turbine blade was cal-culated for fatigue</
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