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Office of Scientific and Technical Information
3:2:1 Crack Spread
Gasoline and Diesel Fuel Update (EIA)
:2:1 Crack Spread :2:1 Crack Spread Figure 1 Source: U.S. Energy Information Administration, based on Thomson Reuters. A crack spread measures the difference between the purchase price of crude oil and the selling price of finished products, such as gasoline and distillate fuel, that a refinery produces from the crude oil. Crack spreads are an indicator of the short-term profit margin of oil refineries because they compare the cost of the crude oil inputs to the wholesale, or spot, prices of the outputs (although they do not include other variable costs or any fixed costs). The 3:2:1 crack spread approximates the product yield at a typical U.S. refinery: for every three barrels of crude oil the refinery processes, it makes two barrels of gasoline and one barrel of distillate
An introduction to crack spreads - Today in Energy - U.S ...
U.S. Energy Information Administration (EIA)
Crack spreads are differences between wholesale petroleum product prices and crude oil prices. These spreads are often used to estimate refining margi ...
Spark Spread
Spark Spread Spark Spread Figure 1 Source: U.S. Energy Information Administration, based on SNL Energy. The spark spread is a common metric for estimating the profitability of natural gas-fired electric generators. The spark spread is the difference between the price received by a generator for electricity produced and the cost of the natural gas needed to produce that electricity. It is typically calculated using daily spot prices for natural gas and power at various regional trading points. The chart above shows spark spreads during 2012, calculated for four locations around the United States. Spark spreads tend to be fairly volatile, more so than crack spreads in petroleum markets, largely because of the volatility of wholesale electric power prices, which vary widely
Cracking knuckles
NLE Websites -- All DOE Office Websites (Extended Search)
Cracking knuckles Cracking knuckles Name: Renee Knuckles Location: N/A Country: N/A Date: N/A Question: Does cracking your joints especially the knuckles cause arthritis? What are some of the results of doing so? Replies: Cracking knuckles has NEVER been associated with causing arthritis. This concept is as wrong as saying weight lifting makes you short, or playing basketball makes you tall. The "popping" of the knuckles results from forcing joint fluid to very rapidly pass from one side of the joint to the other, where the "sides" are partitioned off by the main bones of the joint. Let me rephrase that: a joint is an area where two or more separate and distinct bones meet. The joint fluid provides a cushioning between the joints so that they don't grate into each other. Cracking your knuckles forces the joint fluid from one part of the joint to another, and the popping sound is just the result of the high pressured rushing of fluid.
Hydrogen Assisted Cracking
Science Conference Proceedings (OSTI)
Environmentally Assisted Cracking (EAC): Laboratory Research and Field Experiences: Hydrogen Assisted Cracking Program Organizers: Suresh Divi, TIMET
Creep Crack Growth
Table 3 Creep crack growth constants b and m for various ferritic steels...and Banerji, �??Creep Crack Growth Behavior
Environmentally Assisted Cracking: Nuclear
About this Symposium. Meeting, Materials Science & Technology 2014. Symposium, Environmentally Assisted Cracking: Nuclear. Sponsorship. Organizer(s)�...
Spark Spread - Energy Information Administration
The spark spread is a common metric for estimating the profitability of natural gas-fired electric generators. The spark spread is the difference between the price ...
Studies on upward flame spread.
E-Print Network (OSTI)
??Experimental techniques have been used to investigate three upward flame spread phenomena of particular importance for fire safety applications. First, rates of upward flame spread� (more)
Gollner, Michael J.
Cracks Cleave Crystals
The problem of finding what direction cracks should move is not completely solved. A commonly accepted way to predict crack directions is by computing the density of elastic potential energy stored well away from the crack tip, and finding a direction of crack motion to maximize the consumption of this energy. I provide here a specific case where this rule fails. The example is of a crack in a crystal. It fractures along a crystal plane, rather than in the direction normally predicted to release the most energy. Thus, a correct equation of motion for brittle cracks must take into account both energy flows that are described in conventional continuum theories and details of the environment near the tip that are not.
Michael Marder
LPG storage vessel cracking experience
SciTech Connect
In order to evaluate liquefied petroleum gas (LPG) handling and storage hazards, Caltex Petroleum Corp. (Dallas) surveyed several installations for storage vessel cracking problems. Cracking was found in approximately one-third of the storage vessels. In most cases, the cracking appeared to be due to original fabrication problems and could be removed without compromising the pressure containment. Several in-service cracking problems found were due to exposure to wet hydrogen sulfide. Various procedures were tried in order to minimize the in-service cracking potential. One sphere was condemned because of extensive subsurface cracking. This article's recommendations concern minimizing cracking on new and existing LPG storage vessels.
Cantwell, J.E. (Caltex Petroleum Corp., P.O. Box 619500, Dallas, TX (US))
As part of an overall company program to evaluate LPG handling and storage hazards the authors surveyed several installations for storage vessel cracking problems. Cracking was found in approximately one third of the storage vessels. In most cases the cracking appeared due to original fabrication problems and could be removed without compromising the pressure containment. Several in-service cracking problems due to exposure to wet hydrogen sulfide were found. Various procedures were tried in order to minimize the in-service cracking potential. One sphere was condemned because of extensive subsurface cracking. Recommendations are made to minimize cracking on new and existing LPG storage vessels.
Cantwell, J.E.
Corrosion Fatigue Crack Growth and Stress-Corrosion Cracking in ...
Abstract Scope, The high stress ratio (R=0.85) corrosion fatigue crack growth kinetics and stress-corrosion cracking resistance of sensitized (70-175 �C up to�...
Studies on upward flame spread
5.7 Flame Heights . . . . . . . . . . . . . . . . . .3.4.1 Flame Heights . . . . . . . . . . . . . . 3.5Chapter 4 Upward Flame Spread of an Inclined Fuel Surface
Angle of crack propagation for a vertical hydraulic fracture
DOE Green Energy (OSTI)
Using the strain-energy-density-factor (S) theory, the positive fracture angle +theta/sub o/ (the initial fracture angle of crack propagation) of a near-vertical crack is predicted by using the opening- and sliding-mode stress-intensity factors in the presence of the overburden pressure, the least in situ horizontal principal stress, and the borehole fluid pressure. The crack spreads in the positive theta/sub o/ direction (counter-clockwise) in the plane for which S is a minimum, S/sub min/. It was verified that S/sub min/ is greater than or equal to S/sub c/. The quantity S/sub c/ is defined as the critical value of S, and remains essentially constant. Of interest is the numerical example for calculating fracture angle and the critical uniform borehole fluid pressure required to initiate fracture at such an angle for the present LASL Dry Hot Rock Geothermal Energy Program. (auth)
Sarda, J.P.; Hsu, Y.C.
Analysis of Cracked Pipe Weldments
EPRI estimation formulas for predicting loads necessary for crack initiation and instability can facilitate leak-before-break analysis of cracked nuclear piping. Finite-element calculations carried out in this study verified the accuracy of these formulas for analyzing through-the-wall cracks in bimetallic weldments.
Catalytic cracking process
Processes and apparatus for providing improved catalytic cracking, specifically improved recovery of olefins, LPG or hydrogen from catalytic crackers. The improvement is achieved by passing part of the wet gas stream across membranes selective in favor of light hydrocarbons over hydrogen.
Lokhandwala, Kaaeid A. (Union City, CA); Baker, Richard W. (Palo Alto, CA)
Shale oil cracking. 1. Kinetics
Experiments were conducted to determine kinetics for thermal cracking of shale oil vapor over shale. Cracking temperatures of 504 to 610/sup 0/C and residence times of 2 to 11 seconds were used. A first-order Arrhenius rate expression and stoichiometry were obtained. Also observed were changes in the oil quality. Cracking decreased the H/C ratio, increased the nitrogen content, and decreased the pour point of the oil. Gas-phase oil cracking is contrasted to liquid-phase oil coking as a loss mechanism in oil-shale retorting.
Burnham, A.K.; Taylor, J.R.
Analysis of Crack Growth Data
Table 3 Methods for calculating crack growth rates...the derivative at the midpoint of a data set. These methods use
Environmentally Assisted Cracking of Materials
In-Situ Repairs of Oil Industry Pipelines, Tanks and Vessels by Welding Using Metal Arc Welding Under Oil (MAW-UO) � Interpretation of Crack Initiation and�...
PICEP: Pipe Crack Evaluation Program
We describe a computer program that calculates the crack-opening area, the critical (stable) crack length and the two-phase flow rate through cracks in ductile stainless steel pipes and steam generator tubes. The program is useful in performing leak-before-break calculations in order to demonstrate detectable leak rates prior to a through-wall flaw reaching critical size. Necessary input to the code includes a definition of material properties, loads, thermal-hydraulic conditions, pipe geometry, and crack orientation. User information is provided in the report.
Norris, D.; Okamoto, A.; Chexal, B.; Griesbach, T.
Development of Alternating Current Potential Drop (ACPD) method for the detection of Primary Water Stress Corrosion Cracking initiation in Stainless Steels and�...
Effect of Thermomechanical Processing on Fatigue Crack ...
gechanical driving force such as crack opening distance (COD) . However, at hold time loading, the crack growth rate is drastically decreased with an increase of�...
Weldability Tests for Evaluating Cracking Susceptibility
Table 2 Weldability tests used to evaluate susceptibility to cracking...used to evaluate susceptibility to cracking Test Fields of use Controllable variables Type of data Specialized equipment Relative cost Lehigh restraint test Weld metal hot and cold cracking, root cracking,
Intergranular Stress Corrosion Cracking (IGSCC) Mechanism of ...
About this Abstract. Meeting, Materials Science & Technology 2012. Symposium, Environmentally Assisted Cracking of Materials. Presentation Title�...
Spreading of a granular droplet.
The influence of controlled vibrations on the granular rheology is investigated in a specifically designed experiment in which a granular film spreads under the action of horizontal vibrations. A nonlinear diffusion equation is derived theoretically that describes the evolution of the deposit shape. A self-similar parabolic shape (the granular droplet) and a spreading dynamics are predicted that both agree quantitatively with the experimental results. The theoretical analysis is used to extract effective friction coefficients between the base and the granular layer under sustained and controlled vibrations. A shear thickening regime characteristic of dense granular flows is evidenced at low vibration energy, both for glass beads and natural sand. Conversely, shear thinning is observed at high agitation.
Sanchez, I.; Raynaud, F.; Lanuza, J.; Andreotti, B.; Clement, E.; Aranson, I. S.; Materials Science Division; Univ. Simon; CNRS-ESPCI-Univ.
Stable crack growth estimates based on effective crack length and crack-opening displacements
A method was developed for estimating the amount of stable crack growth that has occurred in a fracture toughness specimen that were loaded into the plastic range and for which only a monotonically increasing load-displacement curve was measured. The method was applied to data from several pressure vessel steels. The resulting J vs ..delta..a values compare favorably with a resistance curve obtained by the multiple specimen heat-tinting technique for A533, Grade B, Class 1 steel. The method for estimating stable crack growth uses several existing concepts heretofore mainly used separately. These concepts include an approximate expression for J for the compact specimen proposed by Andrews, the effective crack length concept of McCabe and Landes, the UK representation of the crack profile as a pair of straight lines intersecting at a hinge point, and Well's expression, J = m sigma/sub y/delta, for relating the crack-opening displacement to the value of J. The value of the constraint factor, m, at the advancing crack tip is estimated by means of a relation between ductility and fracture toughness. When calculated with respect to the COD at the original fatigue crack tip, the constraint factor, m/sub o/, is found to have a value consistently close to 2.0 for compact and precracked Charpy specimens. The method of estimation requires no auxiliary load-deflection measurements or calculations, and so permits single specimen estimates of stable crack growth to be made without the necessity of making high precision unloading compliance measurements.
Merkle, J.G.; Hudson, C.E.
Aspects of Stress Corrosion Cracking Relevant to Irradiation-Assisted Stress Corrosion Cracking (IASCC)
This report provides a comprehensive survey of crack initiation issues in irradiation-assisted stress corrosion cracking (IASCC). It considers microcracking on smooth specimens and the transition from microcracking to stable crack propagation.
Worldwide Measurements of Directional Wave Spreading
The directional spreading of waves is important for both theoretical and practical reasons. Enough measurements have now been made to draw conclusions about the behavior of wave spreading at sites in different climatic regimes. The measurements ...
George Z. Forristall; Kevin C. Ewans
News: Stuxnet: rumours increase, infections spread
The Stuxnet worm which targets Siemens SCADA systems is still spreading and also rapidly building a mythology around itself.
Network forensics: random infection vs spreading epidemic
Computer (and human) networks have long had to contend with spreading viruses. Effectively controlling or curbing an outbreak requires understanding the dynamics of the spread. A virus that spreads by taking advantage of physical links or user-acquaintance ... Keywords: epidemic process, network inference
Chris Milling; Constantine Caramanis; Shie Mannor; Sanjay Shakkottai
Pricing and hedging Asian basket spread options
Asian options, basket options and spread options have been extensively studied in the literature. However, few papers deal with the problem of pricing general Asian basket spread options. This paper aims to fill this gap. In order to obtain prices and ... Keywords: 91G20, Asian basket spread option, Moment matching, Non-comonotonic sum, Shifted log-extended skew normal law
Griselda Deelstra; Alexandre Petkovic; Mich�le Vanmaele
Predicting the Behavior of Small Fatigue Cracks - Programmaster.org
are effective at providing crack propagation resistance in many materials and composites, these mechanisms result in a crack size dependence (i.e., �small crack�...
Valuation of a Spark Spread:
analysis and data in this paper was prepared for a consulting client and we are grateful that they have allowed us to adapt our report in the form of this academic paper. We have modified the plant-specific results in Section 8 to protect the proprietary data and property of our client. 1 1 Executive Summary This paper analyzes a power plant in Alberta, Canada, that is powered by two General Electric LM6000 gas turbines combined with a steam generator that allows combined cycle operations. The LM6000 is derived from a GE engine used on Boeing 767 and 747 airplanes, and is adapted for natural gas by General Electric. This power plant is popular in various power jurisdictions around the world as a turnkey power plant that can offer peaking capacity, and some baseload power delivery. We consider 4 operating modes for the plant: cold metal (off), 15 MW idle in combined cycle, full simple-cycle power (95 MW) and combined cycle full power (120 MW). It is common to refer to such a plant as generating a spark spread: converting natural gas to electricity by burning. A spark spread has two correlated stochastic variables: electricity price and natural gas price. To lower the dimensionality of the problem, we
An Lm Power Plant; Mark Cassano; Gordon Sick
Nonlinear structural crack growth monitoring
DOE Patents (OSTI)
A method and apparatus are provided for the detection, through nonlinear manipulation of data, of an indicator of imminent failure due to crack growth in structural elements. The method is a process of determining energy consumption due to crack growth and correlating the energy consumption with physical phenomena indicative of a failure event. The apparatus includes sensors for sensing physical data factors, processors or the like for computing a relationship between the physical data factors and phenomena indicative of the failure event, and apparatus for providing notification of the characteristics and extent of such phenomena.
Welch, Donald E. (Oak Ridge, TN); Hively, Lee M. (Philadelphia, TN); Holdaway, Ray F. (Clinton, TN)
3:2:1 Crack spreads based on WTI & LLS crude oils have diverged in ...
Crude oil, gasoline, heating oil, diesel, propane, ... such as LLS, which compete with imported grades whose prices are linked to Brent prices. ...
Intergranular Cracking of Brass Sprinkler Heads
Symposium, Charles R. Morin Memorial Symposium on Failure Analysis and Prevention. Presentation Title, Intergranular Cracking of Brass Sprinkler Heads.
Environmental Effects on Fatigue Crack Growth Rates in Sour ...
Environmentally Assisted Cracking of Carbon Steel in High Temperature Geothermal Well � Evaluation of the Susceptibility to Hydrogen Assisted Cracking in�...
Environmental Cracking Resistance of High Nickel Alloys (CRAs
On Modeling Hydrogen-Induced Intergranular Cracking under ...
Corrosion and Cracking of Carbon Steel in Fuel Grade Ethanol
Evaluation of the Susceptibility to Hydrogen Assisted Cracking in ...
On the Fatigue Crack Propagation Behavior of Superalloys at ...
ON THE FATIGUE CRACK PROPAGATION BEHAVIOR. OF SUPERALLOYS AT ... the FCP resistance of superalloys ... lead to poor crack propagation behavior.
Stress Corrosion Cracking of Brass: A Comparative Study on ...
Multicarrier Orthogonal Spread-Spectrum (MOSS) Data ...
Multicarrier Orthogonal Spread-Spectrum (MOSS) Data Transmission Method Note: The technology described above is an early stage opportunity. Licensing rights to this ...
Discrete-event modelling of fire spreading
We deal here with the application of discrete-event System Specification (DEVS) formalism to implement a semi-physical fire spread model. Currently, models from physics finely representing forest fires are not efficient and still under development. If ... Keywords: Cellular models, DEVS, Discrete-event modelling and simulation, Fire spread
Alexandre Muzy; Eric Innocenti; Antoine Aiello; Jean-Fran�ois Santucci; Thierry Marcelli; Paul Antoine Santoni
The influence of cracks in rotating shafts
In this paper, the influence of transverse cracks in a rotating shaft is analysed. The paper addresses the two distinct issues of the changes in modal properties and the influence of crack breathing on dynamic response during operation. Moreover, the evolution of the orbit of a cracked rotor near half of the first resonance frequency is investigated. The results provide a possible basis for an on-line monitoring system. In order to conduct this study, the dynamic response of a rotor with a breathing crack is evaluated by using the alternate frequency/time domain approach. It is shown that this method evaluates the nonlinear behaviour of the rotor system rapidly and efficiently by modelling the breathing crack with a truncated Fourier series. The dynamic response obtained by applying this method is compared with that evaluated through numerical integration. The resulting orbit during transient operation is presented and some distinguishing features of a cracked rotor are examined.
Jean-Jacques Sinou; A. W. Lees
Quench Cracking Characterization of Superalloys Using Fracture ...
When the on-cooling thermal stress. (load) accumulated to a certain point, quench cracking happened abruptly. Based on the precrack length, the thermal stress�...
Environmentally Assisted Cracking Susceptibility Assessment of AP ...
Presentation Title, Environmentally Assisted Cracking Susceptibility Assessment of AP 1000 Reactor Coolant Pump Flywheel Retainer Ring A289 18Cr-18Mn�...
Sulfide Stress Cracking in Steels - A Review
Symposium, Corrosion and Corrosion Protection of Materials in the Oil and Gas Industry. Presentation Title, Sulfide Stress Cracking in Steels - A Review.
Evaluation of Stress-Corrosion Cracking
Table 3 Stress-corrosion cracking of selected material systems...chlorides, seawater Oil/gas production and transmission, oil refining,
Crystallographic Orientation Dependence of Fatigue Crack ...
In the present study, fatigue crack propagation behavior of rolled AZ31B magnesium ... Alloy Design for Enhancing the Fracture Resistance of Heat Treated High�...
Stress Corrosion Cracking - Programmaster.org
Oct 28, 2013 ... Atomic Ordering in Alloy 690 and Its Effect on Long-term Structural Stability and Stress Corrosion Cracking Susceptibility: Michael Kaufman1;�...
Creep Crack Growth Behaviour of Alloy 718
its creep crack growth is controlled by stress intensity factor regardless of load level .... energy. Since vacancies diffuse from a low strain energy position to a high�...
Status Review of Initiation of Environmentally Assisted Cracking and Short Crack Growth
This report reviews current knowledge of environmentally assisted cracking EAC initiation and short crack growth by stress corrosion cracking, strain-induced corrosion cracking, and, to a lesser extent, corrosion fatigue in nickel base alloys, austenitic stainless steels, and carbon and low-alloy steels exposed to typical pressurized water reactor PWR and boiling water reactor BWR aqueous environments. The document identifies key gaps in knowledge and recommends areas where additional experimental work i...
Discontinuous surface cracks during stress corrosion cracking of stainless steel single crystal
Discontinuous surface cracks during stress corrosion cracking of stainless steel single crystal L Keywords: A. Stainless steel B. SEM C. Stress corrosion a b s t r a c t Single crystal 321 stainless steel, and the river-markings exhibited microshear facets along the {1 1 1} plane. Interaction between the main crack
Volinsky, Alex A.
Spread Calibration of Ensemble MOS Forecasts
Ensemble forecasting systems often contain systematic biases and spread deficiencies that can be corrected by statistical postprocessing. This study presents an improvement to an ensemble statistical postprocessing technique, called ensemble ...
Bruce A. Veenhuis
Mixing and Spreading of the Mediterranean Outflow
Hydrographic and current profiler data taken during the 1988 Gulf of Cadiz Expedition have been analyzed to diagnose the mixing, spreading, and descent of the Mediterranean outflow. The ?�S properties and the thickness and width of the outflow ...
Molly O�Neil Baringer; James F. Price
Characterization of Environment-Dependent Fatigue Crack Growth ...
at high frequency levels to fully environment-dependent at very low frequency ... environment-dependent crack growth process, crack increment per cycle is�...
Characterization of Elevated Temperature Fatigue Crack Growth Rates
temperature fatigue and the crack growth rates may be adequately correlated with the ... During creep crack growth the use of rate dependent elastic/plastic frac-.
The Effect of Microstructure on the Fatigue Crack Growth Resistance ...
GROWTH RESISTANCE OF NICKEL BASE SUF'RRALLOYS. Randy Bowman ... damage are most resistant to crack growth. ... crack propagation. (FCP) was�...
High cycle fatigue and fatigue crack propagation behavior of ...
And fatigue crack propagation rates of modified A7075 showed slightly lower. Those superior fatigue strength and resistance of fatigue crack propagation of�...
Computational Weld Mechanics of Hot Crack Nucleation in Nickel ...
Abstract Scope, Computational weld mechanics (CWM) is used to estimate the likelihood of hot crack nucleation in a welded joint. A hot crack nucleates when�...
Modeling of LNG Pool Spreading and Vaporization
In this work, a source term model for estimating the rate of spreading and vaporization of LNG on land and sea is introduced. The model takes into account the composition changes of the boiling mixture, the varying thermodynamic properties due to preferential boiling within the mixture and the effect of boiling on conductive heat transfer. The heat, mass and momentum balance equations are derived for continuous and instantaneous spills and mixture thermodynamic effects are incorporated. A parameter sensitivity analysis was conducted to determine the effect of boiling heat transfer regimes, friction, thermal contact/roughness correction parameter and VLE/mixture thermodynamics on the pool spreading behavior. The aim was to provide a better understanding of these governing phenomena and their relative importance throughout the pool lifetime. The spread model was validated against available experimental data for pool spreading on concrete and sea. The model is solved using Matlab for two continuous and instantaneous spill scenarios and is validated against experimental data on cryogenic pool spreading found in literature.
Basha, Omar 1988-
Interstellar Communication: The Case for Spread Spectrum
Spread spectrum, widely employed in modern digital wireless terrestrial radio systems, chooses a signal with a noise-like character and much higher bandwidth than necessary. This paper advocates spread spectrum modulation for interstellar communication, motivated by robust immunity to radio-frequency interference (RFI) of technological origin in the vicinity of the receiver while preserving full detection sensitivity in the presence of natural sources of noise. Receiver design for noise immunity alone provides no basis for choosing a signal with any specific character, therefore failing to reduce ambiguity. By adding RFI to noise immunity as a design objective, the conjunction of choice of signal (by the transmitter) together with optimum detection for noise immunity (in the receiver) leads through simple probabilistic argument to the conclusion that the signal should possess the statistical properties of a burst of white noise. Thus spread spectrum also provides an implicit coordination between transmitter a...
Messerschmitt, David G
Relationships between HIV spread and evolution examined
3 » 3 » November » Relationships between HIV spread and evolution examined Relationships between HIV spread and evolution examined Thomas Leitner of LANL and collaborators are investigating the development of HIV from the point of contraction onwards. November 14, 2013 Scanning electron micrograph of HIV-1 budding (in green) from cultured lymphocytes. The image has been colored to highlight important features. Photo credit: C. Goldsmith, Centers for Disease Control and Prevention. Scanning electron micrograph of HIV-1 budding (in green) from cultured lymphocytes. The image has been colored to highlight important features. Photo credit: C. Goldsmith, Centers for Disease Control and Prevention. They are examining the relationships between the spread of the virus in a
Chicago Gasoline - WTI Spot Spread - U.S. Energy Information ...
Chicago Gasoline - WTI Spot Spread. Previous slide: Next slide: Back to first slide: View graphic version
Isospin dependence of the. delta. -spreading potential
The ratio of near-resonance inclusive ..pi../sup + -/ scattering cross sections from the isotopic pair /sup 16,18/O is shown to be consistent with an isospin dependence of the ..delta..-spreading potential determined by intermediate coupling to the pion absorption channel.
Karaoglu, B.; Karapiperis, T.; Moniz, E.J.
Information architecture using asymmetric in spreading activation
As products are getting more diverse and new products are entering the market faster, customers have trouble learning how to use them. User-oriented menu structures may solve this problem. Therefore, to design user-oriented information architectures, ... Keywords: asymmetric transition, information architecture, mental model, menu structure, spreading activation theory, user centered design
Se Eung Oh; Jong Soon Park; Rohae Myung
Numerical modeling of crack reorientation and link-up
The FRANC3D/BES software system has been used to simulate the reorientation and link-up of hydraulic fractures in three-dimensional (3D) problems. The adopted technique only needs to discretize the body surface and the crack surface. The crack propagation ... Keywords: FRANC3D/BES, crack propagation, multiple cracks
C. Y. Dong; C. J. de Pater
Diverse spreading behavior of binary polymer nanodroplets.
Molecular dynamics simulations are used to study the spreading of binary polymer nanodroplets in a cylindrical geometry. The polymers, described by the bead-spring model, spread on a flat surface with a surface-coupled Langevin thermostat to mimic the effects of a corrugated surface. Each droplet consists of chains of length 10 or 100 monomers with {approx}350,000 monomers total. The qualitative features of the spreading dynamics are presented for differences in chain length, surface interaction strength, and composition. When the components of the droplet differ only in the surface interaction strength, the more strongly wetting component forms a monolayer film on the surface even when both materials are above or below the wetting transition. In the case where the only difference is the polymer chain length, the monolayer film beneath the droplet is composed of an equal amount of short chain and long chain monomers even when one component (the shorter chain length) is above the wetting transition and the other is not. The fraction of short and long chains in the precursor foot depends on whether both the short and the long chains are in the wetting regime. Diluting the concentration of the strongly wetting component in a mixture with a weakly wetting component decreases the rate of diffusion of the wetting material from the bulk to the surface and limits the spreading rate of the precursor foot, but the bulk spreading rate actually increases when both components are present. This may be due to the strongly wetting material pushing out the weakly wetting material as it moves toward the precursor foot.
Webb, Edmund Blackburn, III; Grest, Gary Stephen; Heine, David R.
Optimal control of fluid catalytic cracking processes
An investigation was made of the applicability of optimal control theory to the design of control systems for non-linear, multivariable chemical processes. A hypothetical fluid catalytic cracking process was selected as a typical representative of such ...
L. A. Gould; L. B. Evans; H. Kurihara
Environmentally assisted cracking in light water reactors.
This report summarizes work performed by Argonne National Laboratory on fatigue and environmentally assisted cracking (EAC) in light water reactors (LWRs) from January to December 2002. Topics that have been investigated include: (a) environmental effects on fatigue crack initiation in carbon and low-alloy steels and austenitic stainless steels (SSs), (b) irradiation-assisted stress corrosion cracking (IASCC) of austenitic SSs in BWRs, (c) evaluation of causes and mechanisms of irradiation-assisted cracking of austenitic SS in PWRs, and (d) cracking in Ni-alloys and welds. A critical review of the ASME Code fatigue design margins and an assessment of the conservation in the current choice of design margins are presented. The existing fatigue {var_epsilon}-N data have been evaluated to define the effects of key material, loading, and environmental parameters on the fatigue lives of carbon and low-alloy steels and austenitic SSs. Experimental data are presented on the effects of surface roughness on fatigue crack initiation in these materials in air and LWR environments. Crack growth tests were performed in BWR environments on SSs irradiated to 0.9 and 2.0 x 10{sup 21} n x cm{sup -2}. The crack growth rates (CGRs) of the irradiated steels are a factor of {approx}5 higher than the disposition curve proposed in NUREG-0313 for thermally sensitized materials. The CGRs decreased by an order of magnitude in low-dissolved oxygen (DO) environments. Slow-strain-rate tensile (SSRT) tests were conducted in high-purity 289 C water on steels irradiated to {approx}3 dpa. The bulk S content correlated well with the susceptibility to intergranular SCC in 289 C water. The IASCC susceptibility of SSs that contain >0.003 wt. % S increased drastically. bend tests in inert environments at 23 C were conducted on broken pieces of SSRT specimens and on unirradiated specimens of the same materials after hydrogen charging. The results of the tests and a review of other data in the literature indicate that IASCC in 289 C water is dominated by a crack-tip grain-boundary process that involves S. An initial IASCC model has been proposed. A crack growth test was completed on mill annealed Alloy 600 in high-purity water at 289 C and 320 C under various environmental and loading conditions. The results from this test are compared with data obtained earlier on several other heats of Alloy 600.
Chopra, O. K.; Chung, H. M.; Clark, R. W.; Gruber, E. E.; Shack, W. J.; Soppet, W. K.; Strain, R. V.
Effect of Hot Cracks on EAC Crack Initiation and Growth in Nickel ...
No crack initiation/extension from hot cracks occured in any weld metals, which is ... Applicability of Lean Grade of Duplex Stainless Steels in Nuclear Power Plants .... Wear of Zircaloy-4 Grid Straps Due to Fretting and Periodic Impact with RV�...
Concrete containment structures and cement-based fills and waste forms are used at the Savannah River Site to enhance the performance of shallow land disposal systems designed for containment of low-level radioactive waste. Understanding and measuring transport through cracked concrete is important for describing the initial condition of radioactive waste containment structures at the Savannah River Site (SRS) and for predicting performance of these structures over time. This report transmits the results of a literature review on transport through cracked concrete which was performed by Professor Jason Weiss, Purdue University per SRR0000678 (RFP-RQ00001029-WY). This review complements the NRC-sponsored literature review and assessment of factors relevant to performance of grouted systems for radioactive waste disposal. This review was performed by The Center for Nuclear Waste Regulatory Analyses, San Antonio, TX, and The University of Aberdeen, Aberdeen Scotland and was focused on tank closure. The objective of the literature review on transport through cracked concrete was to identify information in the open literature which can be applied to SRS transport models for cementitious containment structures, fills, and waste forms. In addition, the literature review was intended to: (1) Provide a framework for describing and classifying cracks in containment structures and cementitious materials used in radioactive waste disposal, (2) Document the state of knowledge and research related to transport through cracks in concrete for various exposure conditions, (3) Provide information or methodology for answering several specific questions related to cracking and transport in concrete, and (4) Provide information that can be used to design experiments on transport through cracked samples and actual structures.
Langton, C.
Laboratory tests were conducted to investigate the stress corrosion cracking (SCC) of 304L stainless steel used to construct the containment vessels for the storage of plutonium-bearing materials. The tear drop corrosion specimens each with an autogenous weld in the center were placed in contact with moist plutonium oxide and chloride salt mixtures. Cracking was found in two of the specimens in the heat affected zone (HAZ) at the apex area. Finite element analysis was performed to simulate the specimen fabrication for determining the internal stress which caused SCC to occur. It was found that the tensile stress at the crack initiation site was about 30% lower than the highest stress which had been shifted to the shoulders of the specimen due to the specimen fabrication process. This finding appears to indicate that the SCC initiation took place in favor of the possibly weaker weld/base metal interface at a sufficiently high level of background stress. The base material, even subject to a higher tensile stress, was not cracked. The relieving of tensile stress due to SCC initiation and growth in the HAZ and the weld might have foreclosed the potential for cracking at the specimen shoulders where higher stress was found.
Lam, P; Philip Zapp, P; Jonathan Duffey, J; Kerry Dunn, K
The Relationship between Ensemble Spread and Ensemble Mean Skill
Statistical considerations suggest that 1) even for a perfect ensemble (one in which all sources of forecast error are sampled correctly) there need not be a high correlation between spread and skill, 2) the correlation between spread and skill ...
Jeffrey S. Whitaker; Andrew F. Loughe
How Do You Spread the Word About Saving Energy? | Department...
Energy.gov (U.S. Department of Energy (DOE)) Indexed Site
Spread the Word About Saving Energy? How Do You Spread the Word About Saving Energy? May 25, 2012 - 2:03pm Addthis Earlier this week, Drew talked about how you can follow Energy...
Alternative Fuels Data Center: EV Charging Stations Spread Through Philly
Alternative Fuels and Advanced Vehicles Data Center (EERE)
EV Charging Stations EV Charging Stations Spread Through Philly to someone by E-mail Share Alternative Fuels Data Center: EV Charging Stations Spread Through Philly on Facebook Tweet about Alternative Fuels Data Center: EV Charging Stations Spread Through Philly on Twitter Bookmark Alternative Fuels Data Center: EV Charging Stations Spread Through Philly on Google Bookmark Alternative Fuels Data Center: EV Charging Stations Spread Through Philly on Delicious Rank Alternative Fuels Data Center: EV Charging Stations Spread Through Philly on Digg Find More places to share Alternative Fuels Data Center: EV Charging Stations Spread Through Philly on AddThis.com... March 3, 2012 EV Charging Stations Spread Through Philly W atch how Philadelphia fuels electric vehicles with a growing network of
Adsorbent-treated cat cracked gasoline in motor fuels
A methof is described for supressing carburetor deposit formation of motor fuels containing untreated cat cracked gasoline by blending adsorbent-treated cat cracked gasoline into the motor fuel. Up to about 50 percent by weight of the total composition is adsorbent treated cat cracked gasoline, but preferably from about 5 to about 25 percent by weight of the total composition is adsorbent treated cat cracked gasoline. In a preferred embodiment a standard reference fuel capable of providing a predetermined level of carburetor deposit formation is provided by the addition of either adsorbent-treated cat cracked gasoline, untreated cat cracked gasoline, or aromatic amines to a base fuel.
Thomas, S.P.
Crack detection using resonant ultrasound spectroscopy
This invention is comprised of a method and apparatus for detecting crack-like flaws in components. A plurality of exciting frequencies are generated and applied to a component in a dry condition to obtain a first ultrasonic spectrum of the component. The component is then wet with a selected liquid to penetrate any crack-like flaws in the component. The plurality of exciting frequencies are again applied to the component and a second ultrasonic spectrum of the component is obtained. The wet and dry ultrasonic spectra are then analyzed to determine the second harmonic components in each of the ultrasonic resonance spectra and the second harmonic components are compared to ascertain the presence of crack-like flaws in the component.
Migliori, A.; Bell, T.M.
Specification of Discrete Event Models for Fire Spreading
The fire-spreading phenomenon is highly complex, and existing mathematical models of fire are so complex themselves that any possibility of analytical solution is precluded. Instead, there has been some success when studying fire spread by means of simulation. ... Keywords: Cell-DEVS, Cellular Automata, DEVS, Discrete event simulation, fire spread
Alexandre Muzy; Eric Innocenti; Antoine Aiello; Jean-Fran�ois Santucci; Gabriel Wainer
A Computational Model of Mitigating Disease Spread in Spatial Networks
This study examines the problem of disease spreading and containment in spatial networks, where the computational model is capable of detecting disease progression to initiate processes mitigating infection spreads. This paper focuses on disease spread ... Keywords: Computational Epidemiology, Computer Viruses, Disease Progression, Forest Fires, Spatial Networks
Taehyong Kim; Kang Li; Aidong Zhang; Surajit Sen; Murali Ramanathan
Efficient Response to Cascading Disaster Spreading
We study the effectiveness of recovery strategies for a dynamic model of failure spreading in networks. These strategies control the distribution of resources based on information about the current network state and network topology. In order to assess their success, we have performed a series of simulation experiments. The considered parameters of these experiments are the network topology, the response time delay and the overall disposition of resources. Our investigations are focused on the comparison of strategies for different scenarios and the determination of the most appropriate strategy. The importance of prompt response and the minimum sufficient quantity of resources are discussed as well.
Buzna, L; Helbing, D; Kuehnert, C; Peters, K; Ammoser, Hendrik; Buzna, Lubos; Helbing, Dirk; Kuehnert, Christian; Peters, Karsten
Increasing jet entrainment, mixing and spreading
A free jet of air is disturbed at a frequency that substantially matches natural turbulences in the free jet to increase the entrainment, mixing, and spreading of air by the free jet, for example in a room or other enclosure. The disturbances are created by pulsing the flow of air that creates the free jet at the desired frequency. Such pulsing of the flow of air can be accomplished by sequentially occluding and opening a duct that confines and directs the flow of air, such as by rotating a disk on an axis transverse to the flow of air in the duct. 11 figs.
Farrington, R.B.
A free jet of air is disturbed at a frequency that substantially matches natural turbulences in the free jet to increase the entrainment, mixing, and spreading of air by the free jet, for example in a room or other enclosure. The disturbances are created by pulsing the flow of air that creates the free jet at the desired frequency. Such pulsing of the flow of air can be accomplished by sequentially occluding and opening a duct that confines and directs the flow of air, such as by rotating a disk on an axis transverse to the flow of air in the duct.
Farrington, Robert B. (Wheatridge, CO)
Accelerated Fatigue Crack Growth Behavior of PWA 1480 Single ...
3 456. 610. 1520 30. AK . AKrss. MPa v'?! Fig. 10 Fatigue crack growth rate as a function of AKrss and AK. Prediction of the Microscopic Crack Behavior: An�...
Reading of cracked optical discs using iterative learning control
Optical discs, including Compact Discs (CDs), Digital Versatile Discs (DVDs), and Blu-ray Discs (BDs), can get cracked during storage and usage. Such cracks commonly lead to discontinuities in the data track, potentially preventing reading of the data ...
Maarten Steinbuch; Koos Van Berkel; George Leenknegt; Tom Oomen; Jeroen Van De Wijdeven
Girth Weld Cracking at Ethanol Terminal Facilities - Programmaster ...
About this Abstract. Meeting, Materials Science & Technology 2013. Symposium, Failure Analysis and Prevention. Presentation Title, Girth Weld Cracking at�...
Latent Cracking of Tantalum - Titanium Welds Due to Hydrogen ...
About this Abstract. Meeting, Materials Science & Technology 2012. Symposium, Environmentally Assisted Cracking of Materials. Presentation Title, Latent�...
Puerto Rico Refinery Thermal Cracking/Visbreaking Downstream ...
Puerto Rico Refinery Thermal Cracking/Visbreaking Downstream Charge Capacity as of January 1 (Barrels per Stream Day)
Stress Corrosion Cracking of Steel In Concentrated Nitrate ...
About this Abstract. Meeting, Materials Science & Technology 2011. Symposium, Environmentally Assisted Cracking of Materials. Presentation Title, Stress�...
Interaction between Local Strains and Stress Corrosion Cracks ...
About this Abstract. Meeting, Materials Science & Technology 2013. Symposium, Environmentally Assisted Cracking (EAC): Laboratory Research and Field�...
Stress Corrosion Cracking Observation in API G-105 Grade Drill ...
Environmentally Assisted Cracking of Stainless Steels and Nickel ...
Oct 10, 2012 ... Intergranular Stress Corrosion Cracking (IGSCC) Mechanism of Structural Component Materials in Pressurized Water Reactors : Young Suk�...
stress corrosion cracking of iron and nickel based alloys
This Table of Contents is from Chemistry and Electrochemistry of Corrosion and Stress Corrosion Cracking published by TMS.
U.S. Refinery Thermal Cracking, Visbreaking Downstream Charge ...
U.S. Refinery Thermal Cracking, Visbreaking Downstream Charge Capacity as of January 1 (Barrels per Stream Day)
Guam Refinery Thermal Cracking/Visbreaking Downstream Charge ...
Guam Refinery Thermal Cracking/Visbreaking Downstream Charge Capacity as of January 1 (Barrels per Stream Day)
Guam Refinery Thermal Cracking/Other (including Gas Oil ...
Guam Refinery Thermal Cracking/Other (including Gas Oil) Downstream Charge Capacity as of January 1 (Barrels per Stream Day)
U.S. Refinery Thermal Cracking, Fluid Coking Downstream Charge ...
U.S. Refinery Thermal Cracking, Fluid Coking Downstream Charge Capacity as of January 1 (Barrels per Stream Day)
Molecular Dynamics of Fatigue Crack Growth in Nanocrystalline ...
Experimental techniques are prohibitive due to limitations of nano samples and advanced microscopic manipulators. In this study, crack propagation under�...
Fuzzy modeling of fluidized catalytic cracking unit
The paper deals with the fuzzy system identification of reactor-regenerator-stripper-fractionator's (RRSF) section of a fluidized catalytic cracking unit (FCCU). The fuzzy system identification based on the data collected from an operating refinery of ... Keywords: Dynamic fuzzy model, FCCU models, Fuzzy clustering, Fuzzy inference systems, Fuzzy models, Hybrid learning, Mountain clustering, Supervised learning, Unsupervised learning
Mohammad Fazle Azeem; Nesar Ahmad; M. Hanmandlu
Cracked rotor vibrations by multifractal analysis
Multifractal analysis has been used to diagnoze cracked and healthy rotors. Is has been shown that the complexity and regularity criteria of the dynamical systems defined by the multiple scaling of the time series can indicate the damages of the rotating shaft.
Grzegorz Litak; Jerzy T. Sawicki
Strip edge cracking simulation in cold rolling
This research work focuses on a specific defect which occurs during cold rolling of steel strips: edge-serration. Investigations on the industrial processes have led to the conclusion that this defect is the result of the edge-trimming and cold rolling sequences. The aim of this research work is to analyze the effect of the cutting process and the cold rolling on cracks occurrence, especially on strip edges.This study is performed using an experimental testing stand called Upsetting Rolling Test (URT). It allows to reproduce cold rolling contact parameters such as forward slip, reduction ratio and friction coefficients. Specimens sampled near trimmed industrial strip edges are deformed using the URT stand. Two sets of specimens with different stress states, obtained by annealing, are submitted to two reduction passes with extreme forward slips.Scanning electron microscopy observations added to 3D optical surface profiler topographies show that on one hand, forward slip has a major effect on cracks opening. On the other hand, cracks opening decreases according to high roll strip speed gradient. Concerning the heat-treated specimens, no crack appeared after all reduction passes, showing a large influence of the cutting process and consequently of the local stress state in the vicinity of the burnish and fracture regions.
Hubert, C.; Dubar, L.; Dubar, M.; Dubois, A. [Univ Lille Nord de France, F-59000 Lille (France); UVHC, TEMPO EA 4542, F-59313 Valenciennes (France)
Digital radiographic systems detect boiler tube cracks
Boiler water wall leaks have been a major cause of steam plant forced outages. But conventional nondestructive evaluation techniques have a poor track record of detecting corrosion fatigue cracking on the inside surface of the cold side of waterwall tubing. EPRI is performing field trials of a prototype direct-digital radiographic system that promises to be a game changer. 8 figs.
Walker, S. [EPRI, Charlotte, NC (United States)
Segmentation of cracks in shale rock
In this paper the use of morphological connected filters are studied for segmenting sheet- and thread-like cracks in images of shale rock. A volume formed from a stack of 2-D X-ray images is processed using 3-D attributes. The shape-preserving property ...
Erik R. Urbach; Marina Pervukhina; Leanne Bischof
Honeywords: making password-cracking detectable
We propose a simple method for improving the security of hashed passwords: the maintenance of additional ``honeywords'' (false passwords) associated with each user's account. An adversary who steals a file of hashed passwords and inverts the hash function ... Keywords: authentication, chaffing, honeywords, login, password cracking, password hashes, passwords
Ari Juels, Ronald L. Rivest
The influence of crack-imbalance orientation and orbital evolution for an extended cracked Jeffcott rotor
Vibration peaks occurring at rational fractions of the fundamental rotating critical speed, here named Local Resonances, facilitate cracked shaft detection during machine shut-down. A modified Jeffcott-rotor on journal bearings accounting for gravity effects and oscillating around nontrivial equilibrium points is employed. Modal parameter selection allows this linear model to represent first mode characteristics of real machines. Orbit evolution and vibration patterns are analyzed, yielding useful results. Crack detection results indicate that, instead of 1x and 2x components, analysis of the remaining local resonances should have priority; this is due to crack-residual imbalance interaction and to 2x multiple induced origins. Therefore, local resonances and orbital evolution around 1/2, 1/3 and 1/4 of the critical speed are emphasized for various crack-imbalance orientations.
Julio Gomez-Mancilla; Jean-Jacques Sinou; V. R. Nosov; Fabrice Thouverez; A. Zambrano
Stress Corrosion Cracking and Crack Tip Characterization of Alloy X-750 in Light Water Reactor Environments
Stress corrosion cracking (SCC) susceptibility of Inconel Alloy X-750 in the HTH condition has been evaluated in high purity water at 93 and 288�C under Boiling Water Reactor Normal Water Chemistry (NWC) and Hydrogen Water ...
Gibbs, Jonathan Paul
Stress corrosion cracking and crack tip characterization of Alloy X-750 in light water reactor environments
PICEP: Pipe Crack Evaluation Program (Revision 1): Special report
This report describes software for calculating single- or two-phase flow through cracks in pipes and steam generator tubes. Options are available for calculating the crack-opening area and the critical (stable) crack length. The program is useful in performing leak-before-break analysis to demonstrate detectable leak rates prior to crack growth instability. Input to the code includes material properties, loads, thermal-hydraulic conditions, pipe geometry, and crack type and orientation. Theory and user information are provided in this report. 16 refs., 7 figs.
Norris, D.M.; Chexal, B.
Golden Spread Panhandle Wind Ranch | Open Energy Information
Open Energy Info (EERE)
Spread Panhandle Wind Ranch Spread Panhandle Wind Ranch Jump to: navigation, search Name Golden Spread Panhandle Wind Ranch Facility Golden Spread Panhandle Wind Ranch Sector Wind energy Facility Type Commercial Scale Wind Facility Status In Service Owner Golden Spread Electric Cooperative Developer Cielo Energy Purchaser Golden Spread Electric Cooperative Location Wildarado TX Coordinates 35.22770741°, -102.2323751° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":35.22770741,"lon":-102.2323751,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}
Bench scale (1 to 6 gram) methane cracking tests have been performed on a variety of pure elements, some alloys, and SAES{reg_sign} commercial getters St 101, St 198, St 707, St 737, and St 909 to determine methane cracking performance (MCP) of 5% methane in a helium carrier at 700 C, 101.3 kPa (760 torr) with a 10 sccm feed. The MCP was almost absent from some materials tested while others showed varying degrees of MCP. Re, Cr, V, Gd, and Mo powders had good MCP, but limited capacities. Nickel supported on kieselguhr (Ni/k), a Zr-Ni alloy, and the SAES{reg_sign} getters had good MCP in a helium carrier. The MCP of these same materials was suppressed in a hydrogen carrier stream and the MCP of the Zr-based materials was reduced by nitride formation when tested with a nitrogen carrier gas.
Klein, J; Jeffrey Holder, J
Process for magnetic beneficiating petroleum cracking catalyst
A process is described for beneficiating a particulate zeolite petroleum cracking catalyst having metal values in excess of 1000 ppm nickel equivalents. The particulate catalyst is passed through a magnetic field in the range of from about 2 Tesla to about 5 Tesla generated by a superconducting quadrupole open-gradient magnetic system for a time sufficient to effect separation of said catalyst into a plurality of zones having different nickel equivalent concentrations. A first zone has nickel equivalents of about 6,000 ppm and greater, a second zone has nickel equivalents in the range of from about 2000 ppm to about 6000 ppm, and a third zone has nickel equivalents of about 2000 ppm and less. The zones of catalyst are separated and the second zone material is recycled to a fluidized bed of zeolite petroleum cracking catalyst. The low nickel equivalent zone is treated while the high nickel equivalent zone is discarded. 1 figures.
Doctor, R.D.
A process for beneficiating a particulate zeolite petroleum cracking catalyst having metal values in excess of 1000 ppm nickel equivalents. The particulate catalyst is passed through a magnetic field in the range of from about 2 Tesla to about 5 Tesla generated by a superconducting quadrupole open-gradient magnetic system for a time sufficient to effect separation of said catalyst into a plurality of zones having different nickel equivalent concentrations. A first zone has nickel equivalents of about 6,000 ppm and greater, a second zone has nickel equivalents in the range of from about 2000 ppm to about 6000 ppm, and a third zone has nickel equivalents of about 2000 ppm and less. The zones of catalyst are separated and the second zone material is recycled to a fluidized bed of zeolite petroleum cracking catalyst. The low nickel equivalent zone is treated while the high nickel equivalent zone is discarded.
Doctor, Richard D. (Lisle, IL)
Circumferential cracking of steam generator tubes
On April 28, 1995, the U.S. Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 95-03, {open_quote}Circumferential Cracking of Steam Generator Tubes.{close_quote} GL 95-03 was issued to obtain information needed to verify licensee compliance with existing regulatory requirements regarding the integrity of steam generator tubes in domestic pressurized-water reactors (PWRs). This report briefly describes the design and function of domestic steam generators and summarizes the staff`s assessment of the responses to GL 95-03. The report concludes with several observations related to steam generator operating experience. This report is intended to be representative of significant operating experience pertaining to circumferential cracking of steam generator tubes from April 1995 through December 1996. Operating experience prior to April 1995 is discussed throughout the report, as necessary, for completeness.
Karwoski, K.J.
Modelling spreading, vaporisation and dissolution of multi-component pools.
??The present work describes the fundamental extension of an integral pool spreading, vaporisation and dissolution model, part of the Process Hazard Assessment Tool (Phast) software.� (more)
Fernandez, MI
Marcellus natural gas production gains affect spreads between ...
... issues, and trends. FAQs Glossary For ... Marcellus natural gas production gains affect spreads ... Supporting increased use of natural gas for power ...
Use of LLNL-developed laser peening spreads
Use of LLNL-developed laser peening spreads When it made its maiden flight on December 15, the Boeing 787 Dreamliner was powered
Structures for dense, crack free thin films
The process described herein provides a simple and cost effective method for making crack free, high density thin ceramic film. The steps involve depositing a layer of a ceramic material on a porous or dense substrate. The deposited layer is compacted and then the resultant laminate is sintered to achieve a higher density than would have been possible without the pre-firing compaction step.
Jacobson, Craig P. (Lafayette, CA); Visco, Steven J. (Berkeley, CA); De Jonghe, Lutgard C. (Lafayette, CA)
Methane cracking over a bituminous coal char
Methane cracking over a bed of Chinese bituminous coal char was studied using a fixed-bed reactor at atmospheric pressure and temperatures between 1073 and 1223 K. Methane conversion over the fresh char increased with increasing temperature to 90% at 1223 K. Hydrogen was the only gas-phase product that was detected during the experimentation. The char was shown to exert a significant catalytic effect on methane cracking by comparing results from experiments with the raw char and demineralised char as well as from blank experiments using quartz. It was further shown that the ash was not the source of the catalytic effect of the char. However, both methane conversion and hydrogen yield decreased with increasing reaction time, irrespective of other experimental conditions, indicating that the char rapidly became deactivated following the exposure to methane. It was speculated that the deposition of carbon from methane cracking was responsible for this deactivation, which is supported by scanning electron microscopy (SEM) image analysis. It was demonstrated that the catalytic activity of the deactivated char can be partially recovered by burning off the carbon deposits with an oxidizing gas mixture containing 0.46% oxygen. 10 refs., 11 figs., 1 tab.
Zhi-qiang Sun; Jin-hu Wu; Mohammad Haghighi; John Bromly; Esther Ng; Hui Ling Wee; Yang Wang; Dong-ke Zhang [Chinese Academy of Sciences, Taiyuan (China). Institute of Coal Chemistry
Hydrogen Induced Cracking of Drip Shield
One potential failure mechanism for titanium and its alloys under repository conditions is via the absorption of atomic hydrogen in the metal crystal lattice. The resulting decreased ductility and fracture toughness may lead to brittle mechanical fracture called hydrogen-induced cracking (HIC) or hydrogen embrittlement. For the current design of the engineered barrier without backfill, HIC may be a problem since the titanium drip shield can be galvanically coupled to rock bolts (or wire mesh), which may fall onto the drip shield, thereby creating conditions for hydrogen production by electrochemical reaction. The purpose of this scientific analysis and modeling activity is to evaluate whether the drip shield will fail by HIC or not under repository conditions within 10,000 years of emplacement. This Analysis and Model Report (AMR) addresses features, events, and processes related to hydrogen induced cracking of the drip shield. REV 00 of this AMR served as a feed to ''Waste Package Degradation Process Model Report'' and was developed in accordance with the activity section ''Hydrogen Induced Cracking of Drip Shield'' of the development plan entitled ''Analysis and Model Reports to Support Waste Package PMR'' (CRWMS M&O 1999a). This AMR, prepared according to ''Technical Work Plan for: Waste Package Materials Data Analyses and Modeling'' (BSC 2002), is to feed the License Application.
G. De
Risk spreading and US energy development
Who should bear the risks and financial burdens of future energy development. Is government regulation an appropriate mechanism to spread and allocate financial, regulatory, and engineering risks of future large-scale and high-risk energy projects. These two critical questions are examined within the context of the court battles over the Federal Energy Regulatory Administration's precedent-setting attempt to force gas consumers of five major pipelines to finance the Great Plains Coal Gasification Project. Private financing is the most-efficient method of funding investment when the assumptions of perfect competition are reasonably approximated. In the absence of market failures, consumer financing via construction-project surcharges on energy bills has equal efficiency properties, although consumer financing may reduce the project-builders incentives to minimize cost. However, government financing is clearly preferred in the presence of market failures that characterize large-scale, high-risk energy projects. In the case of Great Plains, its high risk and large scale coupled with the security benefits of a successful synfuels demonstration project suggested that government financing was both the most efficient and equitable means of financing Great Plains. That ideal solution ran afoul of the reality of selfinterested corporate behavior, Congressional politics, and bureaucratic expediency. 18 references.
Navarro, P.
Crack tip plasticity in single crystal UO2: Atomistic simulations
The fracture behavior of single crystal uranium dioxide is studied using molecular dynamics simulations at room temperature. Initially, an elliptical notch is created on either {111} or {110} planes, and tensile loading is applied normal to the crack planes. For cracks on both planes, shielding of crack tips by plastic deformation is observed, and crack extension occurs for crack on {111} planes only. Two plastic processes, dislocation emission and phase transformation are identified at crack tips. The dislocations have a Burgers vector of ?110?/2, and glide on {100} planes. Two metastable phases, the so-called Rutile and Scrutinyite phases, are identified during the phase transformation, and their relative stability is confirmed by separate density- functional-theory calculations. Examination of stress concentration near crack tips reveals that dislocation emission is not an effective shielding mechanism. The formation of new phases may effectively shield the crack provided all phase interfaces formed near the crack tips are coherent, as in the case of cracks residing on {110} planes.
Yongfeng Zhang; Paul C. Millett; Michael Tonks; Bulent Biner; Xiang-Yang Liu; David A. Andersson
Role of crack tip shielding in the initiation and growth of long and small fatigue cracks in composite microstructures
The role of crack tip shielding in retarding the initiation and growth of fatigue cracks has been examined in metallic composite microstructures (consisting of hard and soft phases), with the objective of achieving maximum resistance to fatigue. Specifically, duplex ferritic-martensitic structures have been developed in AISI 1008 and 1015 mild steels to promote shielding without loss in strength. The shielding is developed primarily from crack deflection and resultant crack closure, such that unusually high long crack propagation resistance is obtained. It is found that the fatigue threshold ..delta..K/sub TH/ in AISI 1008 can be increased by more than 100 pct to over 20 MPa ..sqrt..m, without sacrifice in strength, representing the highest ambient temperature threshold reported for a metallic alloy to date. Similar but smaller increases are found in AISI 1015. The effect of the dual-phase microstructures on crack initiation and small crack (10 to 1000 ..mu..m) growth, however, is markedly different, characteristic of behavior influenced by the mutual competition of intrinsic and extrinsic (shielding) ''toughening'' mechanisms. Accordingly, the composite microstructures which appear to show the highest resistance to the growth of long cracks, show the lowest resistance to crack initiation and small crack growth. In general, dual-phase steels are found to display remarkable fatigue properties, with fatigue limits as high as 58 pct of the tensile strengths and fatigue thresholds in the range of 13 to 20 MPa..sqrt..m.
Shang, J.K.; Tzou, J.L.; Ritchie, R.O. (Materials and Chemical Sciences Div., Lawrence Berkeley Lab., and Dept. of Materials Science and Mineral Engineering, Univ. of California, Berkeley, CA (US))
Improved Cell-DEVS models for fire spreading analysis
The spread of fire is a complex phenomenon that many have tried to study over the years As one can imagine, the spread of fire depends on many different variables such as the material being burned, the geography of the area, and the weather Here, we ...
Matthew MacLeod; Rachid Chreyh; Gabriel Wainer
Fuzzy decision support system for spread mooring system selection
Spread mooring systems are associated with high level uncertainties and risks during tanker loading/unloading operations. In addition, the design of such complex systems consists of many subjective and imprecise parameters. Therefore, in the present ... Keywords: AHP, Decision making, Fuzzy multiple attribute decision making, Fuzzy set theory, Spread mooring system, TOPSIS
Ayhan Mentes; Ismail Hakki Helvacioglu
Spread spectrum based cooperative communication transceiver on FPGA platform
In this paper we describe the implementation of a spread spectrum based cooperative relaying on an FPGA platform. We focus on a network comprising one source, one or more relays, and one destination. Once the source's message is received by the relays, ... Keywords: FPGA, cognitive radio, cooperative communication, rake receiver, spread spectrum
Babak AzimiSadjadi, Satya Prakash Ponnaluri, Ali Namazi, Siddharth Gaddam, Daniel McCarthy, Paul J. Oleski
Cincinnati Canvassing Spreads Retrofitting Message | Department of Energy
Cincinnati Canvassing Spreads Retrofitting Message Cincinnati Canvassing Spreads Retrofitting Message Cincinnati Canvassing Spreads Retrofitting Message May 28, 2010 - 3:07pm Addthis A volunteer canvasses the Mt. Washington neighborhood to spread awareness about home energy audits in the area. | Photo Courtesy GCEA A volunteer canvasses the Mt. Washington neighborhood to spread awareness about home energy audits in the area. | Photo Courtesy GCEA Lindsay Gsell What are the key facts? With help from the Greater Cincinnati Energy Alliance (GCEA), this resident was able to get his home energy audited for only $50, saving approximately $300 from the average audit cost. Stuart Schaefer's home sits on a quaint, tree-lined street in Wyoming, Ohio. Although he's always enjoyed the neighborhood and his house in the
Hydrogen induced crack growth in Grade-12 titanium
Internal hydrogen induced crack growth rates were measured in Grade-12 titanium which is a candidate material for high-level nuclear waste containers. As-received and hydrogen charged samples (5 ppM to 330 ppM hydrogen) were used for slow crack growth measurements at constant loads using a Krak Gauge. The testing temperature ranged from room temperature to 148/sup 0/C. The crack growth kinetics under low to moderate loads are linear, but this linear rate is interrupted by discrete fast crack jump segments with parabolic or cubic type kinetics. These fast jump segments are thought to be associated with the passage of the crack front through the alpha-beta interface phase or with the initial loading sequence. By measuring striation spacings on the fracture surface, most crack growth rates observed are found to be in stage II. The striations are considered to be associated with hydride fracture. The crack path is either transgranular in the alpha phase or interfacial in the alpha phase adjacent to the beta phase. For transgranular growth, crack growth rates are constant and slower than those for interfacial growth which is associated with fast crack growth through a high hydrogen concentration region. Most stage II crack growth rates depend slightly on the stress intensity suggesting the contribution of plastic tearing process to stage II kinetics. The activation energies for crack growth are much lower than the activation energy of hydrogen diffusion through the alpha phase, implying that hydrogen is transported along dislocations, grain boundaries or interfaces. When the temperature is increased, the crack velocity first reaches a maximum and then decreases at higher temperatures. These temperature effects come from lower hydrogen concentration trapped at dislocations or from slower hydride nucleation kinetics, both at higher temperatures.
Ahn, T.M.; Lee, K.S.
Orientation Effects and Influence of Delta Phase on Fatigue Crack ...
including a hold time at maximum load lead to increased crack propagation rates when compared ... 720�C ;' 8 hours .! controlled cooling rate at 50�C per hour.
Intergranular Liquid Formation, Distribution, and Cracking in the ...
zone adjacent to the fusion zone. These intergranular cracks form when liquid ...... 718, and A286 in Light Water Reactor. Environments",. J. Mater. Eng., 2, pp.
Relationships Between Stress Corrosion Cracking Tests and Utility ...
Aug 1, 1999 ... Several utility steam generator and stress corrosion cracking ... Superheated steam and neutral solution environments are found to be�...
Influence of Different Cooling Structure on Surface Crack of HSLA ...
Presentation Title, Influence of Different Cooling Structure on Surface Crack of .... of Si3N4-SiC Heat Absorption Ceramic Material Used for Tower Type Solar�...
Basic Aspects of Superalloy Design for Crack Growth Resistance
theories for fatigue and creep crack growth resistance that are particularly ... devices as the nuclear reactors and in such strategic and expensive vehicles.
Solidification Cracking Study of High Chromium Nickel-Base Filler ...
... and rank the relative cracking susceptibility of these filler metal specifications. ... Surface Processing of Ag /TiO2 Nanowire Membranes for Solar Photovoltaic�...
Research and Evaluation of Low Temperature Crack Propagation of ...
NRC/EPRI Welding Residual Stress Validation Program (Phase III) � On the Microstructure of Alloy 600 SCC Cracks Observed by TEM on PWR SG Pulled Tubes�...
DPQ Event Cracked Bushing Leads to Transformer Bank Failure
As part of EPRI's distribution power quality (DPQ) project this power quality (PQ) case study investigates cracked bushing recorded by PQ monitors that led to tranformer bank failure.
Stress corrosion cracking of zirconium in nitric acid
The susceptibility of zirconium and its common alloys to stress corrosion cracking (SCC) in nitric acid was investigated by slow strain-rate and constant deflection techniques. Cracking occurred at 25/sup 0/C over a wide range of acid concentrations and electrochemical potentials. The crack velocity increased slightly with increasing temperature. The failure mode was transgranular and the morphology was similar to SCC failures of zirconium alloys in other environments. The fracture was very orientation-dependent suggesting that it occurs on a single crystallographic plane in the material. The results of the study are not consistent with a hydrogen mechanism for cracking.
Beavers, J.A.; Griess, J.C.; Boyd, W.K.
One-Dimensional Cold Rolling Effects on Stress Corrosion Crack ...
A Microstructural Investigation on the Effect of Cold Work on Environmentally .... Stress Corrosion Cracking Behavior near the Fusion Boundary of Dissimilar�...
P wave anisotropy, stress, and crack distribution at Coso geothermal...
P wave anisotropy, stress, and crack distribution at Coso geothermal field, California Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Journal Article: P wave...
Failure Analysis of a Cracked Thermite Welded Rail Section
Brittle fracture followed the fatigue crack propagation causing complete separation of the rail. Although the excess material was thought to reinforce the rails it�...
Thermal Cracking of Large-Diameter 706 Ingots
responsible for the cracking. The most plausible scenario is that residual stresses generated by ... Analysis of Heat Up for Homogenization. Finite Element Model.
High-Temperature Stress Relaxation Cracking and Stress Rupture ...
An incident occurred that resulted in the cracking of gasifier internals, bulging and stress rupture of the shell and the escape of hot syngas, causing a fire.
Corrosion Fatigue and Crack Propagation of Different Austenitic ...
A FIB Study of the Resistance of Grain Boundaries to Short Fatigue Crack Propagation in Three-Dimensions in High Strength Al Alloys � A Non-Linear Damage�...
Effect of Interstitial Content on High Temperature Fatigue Crack ...
instance; resulted in fatigue crack propagation (FCP)' programs like ESDADTA(2) and ENSIP(3). Fatigue resistance of nickel base superalloys is affected by�...
Fatigue and Fatigue Crack Propagation Behaviors of High ...
The S-N fatigue and fatigue crack propagation (FCP) behaviors of high ... The mechanisms associated with the improved fatigue resistance for the high�...
Effect of Thermal-Mechanical Treatment on the Fatigue Crack ...
that fatigue crack propagation (FCP) resistance without holding time has no significant difference between three alloys with 718Plus being the best and 718 the�...
Fatigue Property-Microstructure Relationships and Crack Growth
Feb 28, 2011 ... Effect of Microstructure on Fatigue Behavior of Two Pipeline Steels: .... to a transition crack length (LEFM applicable) is approximated using�...
In-vitro Evaluation of Stress Corrosion Cracking of Biomedical ...
In this study, the susceptibility to stress corrosion cracking of biodegradable and aluminium-free magnesium alloys, WZ21 and WE43, was investigated using�...
Corrosion Inhibition of Stress Corrosion Cracking and Localized ...
Abstract Scope, Stress corrosion cracking of 7050 aluminum alloys in the turbo expander industry can cause expensive catastrophic failures, especially for turbo
Strain Rate Sensitivity of Alloy 718 Stress Corrosion Cracking
Stress corrosion cracking (SCC) tests were conducted in 36O'C pressurized- water-reactor. (PWR) primary water using. Alloy 718 heat-treated to produce.
Stress Corrosion Cracking of Aluminium-Free Magnesium Alloys in ...
Presentation Title, Stress Corrosion Cracking of Aluminium-Free Magnesium Alloys in a Simulated Human Body Fluid. Author(s), Lokesh Choudhary, R. K. Singh�...
Environmentally Assisted Cracking of Alloy 7050-T7451 Exposed to ...
Under cyclic loading notched specimens failed by transgranular stress corrosion cracking. Striations were observed on the cleavage-like facets. The number of�...
Stress Corrosion Crack Initiation of Alloy 690 in Subcritical and ...
Abstract Scope, The objective of this study is to investigate the structure and chemistry of corrosion and stress corrosion crack initiation in Alloy 690. To avoid
grain boundary oxidation and stress corrosion cracking in nickel ...
Accelerated stress corrosion cracking tests and exposures were conducted on alloy 600, Ni-9Fe, and Ni-9Fe-5Cr (LCr) in constant extension rate mode in�...
Model for the Superimposed Effects of Stress-Corrosion Cracking ...
Symposium, Fatigue and Corrosion Damage in Metallic Materials: Fundamentals, ... and a stress-corrosion cracking mode acting at high stress intensity in NaCl.
Stress Corrosion Cracking Threshold of Ti 6-4 Extrusions
Ti 6Al-4V extrusions with standard chemistry and extra low interstitial are evaluated for their stress corrosion cracking resistance. Also examined is the affect of�...
A Study on the Stress Corrosion Cracking Mechanism of Carbon ...
Abstract Scope, Carbon steel is susceptible to stress corrosion cracking (SCC) in fuel grade ethanol (FGE). The research results obtained thus far have found�...
Stress Corrosion Cracking Initiation of Austenitic Alloys in ...
Presentation Title, Stress Corrosion Cracking Initiation of Austenitic Alloys in Supercritical Water. Author(s), Guoping Cao, Vahid Firouzdor, Todd Allen. On-
Galvanic Corrosion and Stress Corrosion Cracking of Steel and ...
No aluminum bolt AW 7075 failed in magnesium due to stress corrosion cracking (SCC). Even aluminum bolts in T6 condition can be used for automotive�...
U.S. Refinery Thermal Cracking, Other (including Gas Oil ...
U.S. Refinery Thermal Cracking, Other (including Gas Oil) Downstream Charge Capacity as of January 1 (Barrels per Stream Day)
Stress Corrosion Cracking of Stabilized Austenitic Stainless Steels ...
Aug 1, 1999 ... Stress Corrosion Cracking of Stabilized Austenitic Stainless Steels in Various Types of Nuclear Power Plants by M.O. Speidel and R.
Ranking the Susceptibility to Hydrogen-assisted Cracking in Super ...
Thus, SDSS welds are exposed to hydrogen charging to under CP. There have been reported hydrogen assisted cracking (HAC) failures in SDSS welds during�...
Hydrogen Induced Cracking Susceptibility of Titanium Alloys in ...
May 16, 2007 ... This report evaluates hydrogen-induced cracking (HIC) susceptibility of titanium alloys in environments anticipated in the Yucca Mountain�...
Short-Crack Response of Alloy 182 Weld Metal Undergoing Stress Corrosion Cracking in High-Temperature PWR Primary Water
Mechanistic investigations of environmentally assisted cracking (EAC), to date, have focused more on propagation relative to initiation. At the same time, components spend most of their life in the initiation and "short-crack" growth regimes. Prior exploratory work conducted at General Electric Global Research Center (GE GRC) showed that stainless steels, Alloy 600, and Alloy 182 weld metal exhibit lower average growth rates when the cracks are very short or small (1050 m). In those tests, the transition...
Information-theoretic-based spreading measures of orthogonal polynomials
The macroscopic properties of a quantum system strongly depend on the spreading of the physical eigenfunctions (wavefunctions) of its Hamiltonian operador over its confined domain. The wavefunctions are often controlled by classical or hypergeometric-type orthogonal polynomials (Hermite, Laguerre and Jacobi). Here we discuss the spreading of these polynomials over its orthogonality interval by means of various information-theoretic quantities which grasp some facets of the polynomial distribution not yet analyzed. We consider the information-theoretic lengths closely related to the Fisher information and R\\'enyi and Shannon entropies, which quantify the polynomial spreading far beyond the celebrated standard deviation.
Jesus S. Dehesa; A. Guerrero; Pablo S�nchez-Moreno
Origin of undesirable cracks during layer transfer
We investigate the origin of undesirable transverse cracks often observed in thin films obtained by the layer transfer technique. During this process, two crystals bonded to each other containing a weak plan produced by ion implantation are heated to let a thin layer of one of the material on the other. The level of stress imposed on the film during the heating phase due to the mismatch of thermal expansion coefficients of the substrate and the film is shown to be the relevant parameter of the problem. In particular, it is shown that if the film is submitted to a tensile stress, the microcracks produced by ion implantation are not stable and deviate from their straight trajectory making the layer transfer process impossible. However, if the compressive stress exceeds a threshold value, after layer transfer, the film can buckle and delaminate, leading to transverse cracks induced by bending. As a result, we show that the imposed stress \\sigma_m - or equivalently the heating temperature - must be within the ran...
Ponson, Laurent; Atwater, Harry; Ravichandran, Guruswami; Bhattacharya, Kaushik
A nanomechanical investigation of the crack tip process zone of marble
This study explores the interaction between crack initiation and nanomechanical properties in the crack tip process zone (zone of microcracking at the tip of a propagating crack) of a brittle geomaterial. Samples of Carrara ...
Brooks, Zenzile (Zenzile Z.)
Fatigue-crack propagation behavior of Inconel 718
The techniques of linear-elastic fracture mechanics were used to characterize the effect of several variables (temperature, environment, cyclic frequency, stress ratio, and heat-treatment variations) upon the fatigue-crack growth behavior of Inconel 718 base metal and weldments. Relevant crack growth data on this alloy from other laboratories is also presented. (33 fig, 39 references) (auth)
James, L.A.
Evaluation of Circumferential Cracking on Supercritical Boiler Waterwalls
Circumferential cracking of the fireside surfaces of supercritical waterwalls remains a problem for many coal-fired boilers. Two parallel test programs at Pennsylvania Power and Light's (PPL) Brunner Island Unit 3 attempted to correlate operating conditions with the development and propagation of circumferential cracks.
Micro-crack Damage Evolution of Fracturing Rock Chaotic Characteristics
Chaotic theory and bifurcation of modern nonlinear science were used to study the evolution of micro-cracks under the hydraulic fracturing of the rock mass characteristics, the tensor damage variable which described the chao evolution of micro-cracks ... Keywords: chaos theory, bifurcation theory, damage evolution
Zhaowan Chun; Wang Tingting
with inherently tight crack widths, typically less than 80 micron, even when strained up to 5% in uniaxial tension to undergo large deformations while maintaining load capacity. Of interest to this study are the tight crack mixture. Mixing proportions of both materials are shown in Table 1. The sand used in ECC had an average
Lepech, Michael D.
Tight Product Balance Pushes Up Product Spread (Spot Product - Crude
5 5 Notes: Gasoline inventories indicate how tight the gasoline product market is in any one region. When the gasoline market is tight, it affects the portion of gasoline price is the spread between spot product price and crude oil price. Note that in late 1998-and early 1999 spreads were very small when inventories were quite high. Contrast summers of 1998 or 1999 with summer 2000. Last summer's tight markets, resulting low stocks and transition to Phase 2 RFG added price pressure over and above the already high crude price pressure on gasoline -- particularly in the Midwest. As we ended last winter, gasoline inventories were low, and the spread between spot prices and crude oil were higher than typical as a result. Inventories stayed well below average and the spread during the
Golden Spread Electric Cooperative, Inc | Open Energy Information
Golden Spread Electric Cooperative, Inc Golden Spread Electric Cooperative, Inc Jump to: navigation, search Name Golden Spread Electric Cooperative, Inc Place Amarillo, Texas Utility Id 7349 Utility Location Yes Ownership C NERC Location SPP NERC ERCOT Yes NERC SPP Yes Operates Generating Plant Yes Activity Generation Yes Activity Transmission Yes Activity Buying Transmission Yes Activity Buying Distribution Yes Activity Wholesale Marketing Yes References EIA Form EIA-861 Final Data File for 2010 - File1_a[1] SGIC[2] LinkedIn Connections CrunchBase Profile No CrunchBase profile. Create one now! This article is a stub. You can help OpenEI by expanding it. Golden Spread Electric Cooperative, Inc. Smart Grid Project was awarded $19,995,000 Recovery Act Funding with a total project value of $49,987,500.
Accelerating Spatially Explicit Simulations of Spread of Lyme Disease
The factors influencing spread of Lyme disease are often studied using computer-based simulations and spatially explicit models. However, simulating large and complex models is a time consuming task, even when parallel simulation techniques are employed. ...
Dhananjai M. Rao; Philip A. Wilsey
Flame spread Analysis using a Variable B-Number
for the Upward Laminar Spread of Flames Over Vertical FuelSurfaces," Combust. Flame, vol. 31, p. 135-148 P. J. PagniA. S. Rangwala, �A Theory of Flame Extinction based on Flame
Rangwala, Ali S.
Intense spreading of radar echoes from ionospheric plasmas
On December 25, 2004, a large-scale ionospheric plasma bubble was observed over Arecibo Observatory in Puerto Rico, inducing significant range spreading on ionograms. This phenomena may be explained by means of the E x B ...
Dorfman, Seth E
Asynchronous Rumour Spreading in Social and Signed Networks
In this paper, we present an experimental analysis of the asynchronous push & pull rumour spreading protocol. This is, to date, the best-performing rumour spreading protocol for simple, scalable, and robust information dissemination in distributed systems. We analyse the effect that multiple parameters have on the protocol's performance, such as varying the rate at which nodes propagate rumours, using memory to avoid contacting the same neighbour twice in a row, varying the stopping criteria used by nodes to decide when to stop spreading the rumour, and others. Prior work has focused on either providing theoretical upper bounds regarding the number of rounds needed to spread the rumour to all nodes, or, proposes improvements by adjusting isolated parameters. To our knowledge, our work is the first to study how all parameters affect system behaviour both in isolation and combination and under a wide range of values. Our analysis is based on experimental simulations using real-world social network datasets,...
Patsonakis, Christos
Spread the word about how to help | ENERGY STAR
Engage occupants Provide a seat at the table Share energy goals and progress Identify energy-saving actions Spread the word about how to help Give incentives and recognition...
Energy Spread Compensation for Multi-Bunch Linac Operation Mode
ENERGY SPREAD COMPENSATION FOR MULTI-BUNCH LINAC OPERATION MODE D. Mihalcea, Northern Illinois University, DeKalb, IL 60115, USA W. Gai, J. G. Power, ANL, Argonne, IL 60439, USA...
Spread narrows between Brent and WTI crude oil benchmark prices ...
Spot prices for benchmarks West Texas Intermediate (WTI) and North Sea Brent crude oil neared parity of around $109 per barrel July 19, and the Brent-WTI spread was ...
A Gravitational Spreading Origin For The Socompa Debris Avalanche | Open
Gravitational Spreading Origin For The Socompa Debris Avalanche Gravitational Spreading Origin For The Socompa Debris Avalanche Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Journal Article: A Gravitational Spreading Origin For The Socompa Debris Avalanche Details Activities (0) Areas (0) Regions (0) Abstract: Socompa Volcano arguably provides the world's best-exposed example of a sector collapse-derived debris avalanche deposit. New observations lead us to re-interpret the origin of the sector collapse. We show that it was triggered by failure of active thrust-anticlines in sediments and ignimbrites underlying the volcano. The thrust-anticlines were a result of gravitational spreading of substrata under the volcano load. About 80% of the resulting avalanche deposit is composed of substrata formerly residing under the volcano and in the anticlines. The collapse
Distillate Supply/Demand Balance Reflected in Spreads
4 4 Notes: The price spike that initiated the flood of distillate imports last winter can be easily seen in this chart. The distillate supply/demand balance influences the spread between spot distillate and spot crude oil prices. For example, when stocks are higher than normal, the spread will be lower than usual. This spread is the price incentive that encourages or discourages changes in supply. The January/February 2000 price spike was shorter than the one last winter, largely due to the timing. Since last winter's price spike occurred early in the season, it took some time before prices receded substantially. Currently, the distillate fuel refining spread (the difference between the spot heating oil price and the WTI price) is more "typical". But as was
Fatigue Crack Closure and Corrosion Fatigue in Al 7075 Alloy Using ...
Traditional methods to quantify crack closure load, such as load-displacement curves, are not very accurate. In this study, the degree of crack closure through�...
A Study on Fatigue-Crack-Deformation Behavior Following a Single ...
Apr 27, 2009 ... Width. Using this method, the respective crack�opening load (COL) at various crack-growth stages can be determined ?om the curve of the�...
Induction Heating Stress Improvement Effectiveness on Crack Growth in Operating Plants (BWRVIP-61)
New reports of intergranular stress corrosion cracking prompted this review of factors that could influence the performance of the pipe cracking remedy known as induction heating stress improvement.
Assessment of Crack in Corrosion Defects in Natural Gas Transmission Pipelines.
??Pipelines are one of the safest forms of transportation for oil and gas. However, pipelines may experience some defects, such as cracks, corrosion and cracks� (more)
Hosseini, Seyed Aliakbar
Insights into Stress Corrosion Cracking Mechanisms from High-Resolution Measurements of Crack-Tip Structures and Compositions
The fundamental basis for mechanistic understanding and modeling of SCC remains in question for many systems. Specific mechanisms controlling SCC can vary with changes in alloy characteristics, applied/residual stress or environmental conditions. The local crack electrochemistry, crack-tip mechanics and material metallurgy are the main factors controlling crack growth. These localized properties are difficult or impossible to measure in active cracks. Nevertheless, it is essential to quantitatively interrogate these crack-tip conditions if mechanistic understanding is to be obtained. A major recent advance has been the ability to investigate SCC cracks and crack tips using high-resolution ATEM techniques. ATEM enables the characterization of SCC cracks including trapped tip solution chemistries, corrosion product/film compositions and structures, and elemental composition gradients and defect microstructures along the crack walls and at the crack tip. A wide variety of methods for imaging and analyses at resolutions down to the atomic level can be used to examine the crack and corrosion film characteristics. Surface films and reaction layers have been examined by cross-sectional TEM techniques, but little work had been conducted on environmentally induced internal cracks until that of Lewis and co-workers [1-3] and the current authors [4-17]. This capability combined with modern ATEM techniques has enabled exciting new insights into corrosion processes occurring at buried interfaces and is being used to identify mechanisms controlling IGSCC in boiling water reactor (BWR) and pressurized water reactor (PWR) components. The objective of this paper is to summarize certain results focused on IGSCC of Fe- base and Ni-base stainless alloys in high-temperature water environments. Representative crack-tip examples will be shown to illustrate specific aspects that are characteristic of SCC in the material/environment combinations. Differences and similarities in crack-tip structures- chemistries will be highlighted comparing Fe-base 316/304SS to Ni-base alloy 600/182 and for tests in oxidizing versus hydrogenated water environments.
Bruemmer, Stephen M.; Thomas, Larry E.
Cracking in liquid petroleum gas Horton spheres
A gas processing plant on the western coast of India produces sweet gas after processing sour natural gas. Liquid petroleum gas (LPG) is recovered from the sweet gas. The LPG, containing a H{sub 2}S concentration of 10 ppm to 20 ppm, is stored in Horton spheres, each 17 m in diameter with a capacity of {minus}27 C to 55 C. Horton spheres for containing liquid petroleum gas (LPG) were fabricated on-site using prestressed plates of high-strength carbon steel (CS) SA 537 Class-1 with post-weld heat treatment. High-residual tensile stresses and hydrogen absorption from H{sub 2}S present in LPG could be the cause of cracking at weld and heat-affected zone interfaces at high hardness locations. Recommendations are given for inspection and use of lower-strength CS and improved welding procedures.
Trivedi, D.K. Gupta, S.C. [Oil and Natural Gas Corp., Surat (India). Hazari Gas Processing Complex
An introduction to spark spreads - Today in Energy - U.S. Energy ...
A model for the (QUASI) steady flame spread on vertical and horizontal surface.
??Initial fire spread is composed of the processes of ignition, flame spread, and burning rate. The effects of a material's thermal characteristics and burning behaviors� (more)
Shi, Yan
Modeling of flame spread over thin fuels on downward configuration in the presence of forced convection.
??The purpose of this thesis is to simulate the downward flame spread over thin fuel (Cellulose and Polymethylmethacrylate) in a natural convection environment. Flame spread� (more)
Patel, Gaurav Rameshbhai
Dark spreads measure returns over fuel costs of coal-fired ...
The dark spread is a common metric used to estimate returns over fuel costs of coal-fired electric generators. A dark spread is the difference between ...
Unlike the common belief that crack propagation behavior can be predicted successfully by employing fracture criteria based on a constant crack tip opening displacement or angle (CTOD/CTOA), this paper shows that the initially non-constant portion of the CTOD/CTOA plays an essential role in predicting the fracture load for a growing crack. Three- and two-dimensional finite element analyses indicate that a severe underestimate of the experimental load vs. crack extension curve would occur if a constant CTOD/CTOA criterion is used. However, the use of a simplified, bilinear CTOD/CTOA criterion including its non-constant portion will closely duplicate the test data. Furthermore, as a result of using the experimental data from J-integral test with various crack length to specimen width ratios (a/W), it is demonstrated that the CTOD/CTOA is crack tip constraint dependent. The initially higher values of the CTOD/CTOA are in fact a natural consequence of crack growth process which is refl ected by the J-resistance curve and its slope (tearing modulus).
Analysis of Alloy 600 and X-750 stress corrosion cracks
A few months ago, KAPL evidence supported the view that Primary or Pure Water Stress Corrosion Cracking (PWSCC) of Alloy 600 results from a hydrogen mechanism. Figure 1 shows an Analytical Electron Microscope (AEM) analysis of a stress corrosion crack (SCC) crack in an A600 split tube U-bend specimen exposed to primary water at 338{degree}C (640{degrees}F) for 462 days. The features which appear to confirm a hydrogen mechanism are: (1) A very narrow (< 200 {angstrom}) crack with a sharp tip, nearly free of deposits. (2) No evidence of severe plastic deformation in the region immediately ahead of the crack tip. (3) A line of small voids preceding the main crack tip, of which the largest is about 5 x 10{sup {minus}6} cm in length. Shen and Shewmon proposed that PWSCC of Alloy 600 occurs due to small microvoids ahead of a main crack tip. The hypothesis is that such voids result from pockets of methane gas formed by the reaction of atomic hydrogen with carbon in the base metal. The voids are about 10 x 10{sup {minus}6} cm diameter, approximately a factor of 2 larger than the largest voids.
Thompson, C.D.; Lewis, N.; Krasodomski, H.
Improved load ratio method for predicting crack length
The elastic compliance from unloading/reloading sequences in a load-displacement record estimates well crack length in elastic-plastic fracture toughness tests of compact tension [C(T)] and bending type specimens. The need for partial unloading of the specimen makes it difficult to run the test under static loading and impossible under either dynamic loading or very high temperatures. Furthermore, fracture toughness testing in which crack length is determined from elastic compliance requires high precision testing equipment and highly skilled technicians. As a result, such tests are confined usually to research laboratories and seldom used under production settings. To eliminate these problems, an improved load ratio method of predicting crack length is proposed that utilizes only the recorded load versus load-line displacement curve (or load versus crack-mouth-opening displacement curve) without unloading/reloading sequences. As a result, the instrumentation is much simpler than in the elastic compliance or potential drop methods. If only a monotonic load-displacement record is to be measured the fracture toughness test becomes almost as simple to perform as a tension test. The method described here improves in three ways the ``original load ratio method`` proposed by Hu et al. First, a blunting term is added to the crack length before maximum load. Second, a strain hardening correction is included after maximum load. And, third, the initial crack length and the physical (final) crack length measured at the end of the test serve to anchor the predicted crack lengths, forcing agreement between predicted and measured values. The method predicts crack extension with excellent accuracy in specimens fabricated from A302, A508, and A533B piping and pressure vessel steels, A588 and A572 structural steels, and HY-80 ship steel.
Chen, X.; Albrecht, P. [Univ. of Maryland, College Park, MD (United States). Inst. for Systems Research; Wright, W. [Federal Highway Administration, McLean, VA (United States). Turner-Fairbank Highway Research Center; Joyce, J.A. [Naval Academy, Annapolis, MD (United States). Mechanical Engineering Dept.
Hydrogen-Induced Cracking of the Drip Shield
Hydrogen-induced cracking is characterized by the decreased ductility and fracture toughness of a material due to the absorption of atomic hydrogen in the metal crystal lattice. Corrosion is the source of hydrogen generation. For the current design of the engineered barrier without backfill, hydrogen-induced cracking may be a concern because the titanium drip shield can be galvanically coupled to rock bolts (or wire mesh), which may fall onto the drip shield, thereby creating conditions for hydrogen production by electrochemical reaction. The purpose of this report is to analyze whether the drip shield will fail by hydrogen-induced cracking under repository conditions within 10,000 years after emplacement. Hydrogen-induced cracking is a scenario of premature failure of the drip shield. This report develops a realistic model to assess the form of hydrogen-induced cracking degradation of the drip shield under the hydrogen-induced cracking. The scope of this work covers the evaluation of hydrogen absorbed due to general corrosion and galvanic coupling to less noble metals (e.g., Stainless Steel Type 316 and carbon steels) under the repository conditions during the 10,000-year regulatory period after emplacement and whether the absorbed hydrogen content will exceed the critical hydrogen concentration value, above which the hydrogen-induced cracking is assumed to occur. This report also provides the basis for excluding the features, events, and processes (FEPs) related to hydrogen-induced cracking of the drip shield with particular emphasis on FEP 2.1.03.04.OB, hydride cracking of drip shields (DTN: M00407SEPFEPLA.000 [DIRS 170760]). This report is prepared according to ''Technical Work Plan (TWP) for: Regulatory Integration Modeling and Analysis of the Waste Form and Waste Package'' (BSC 2004 [DIRS 169944]).
F. Hua
Prediction of Reflection Cracking in Hot Mix Asphalt Overlays
Reflection cracking is one of the main distresses in hot-mix asphalt (HMA) overlays. It has been a serious concern since early in the 20th century. Since then, several models have been developed to predict the extent and severity of reflection cracking in HMA overlays. However, only limited research has been performed to evaluate and calibrate these models. In this dissertation, mechanistic-based models are calibrated to field data of over 400 overlay test sections to produce a design process for predicting reflection cracks. Three cracking mechanisms: bending, shearing traffic stresses, and thermal stress are taken into account to evaluate the rate of growth of the three increasing levels of distress severity: low, medium, and high. The cumulative damage done by all three cracking mechanisms is used to predict the number of days for the reflection crack to reach the surface of the overlay. The result of this calculation is calibrated to the observed field data (severity and extent) which has been fitted with an S-shaped curve. In the mechanistic computations, material properties and fracture-related stress intensity factors are generated using efficient Artificial Neural Network (ANN) algorithms. In the bending and shearing traffic stress models, the traffic was represented by axle load spectra. In the thermal stress model, a recently developed temperature model was used to predict the temperature at the crack tips. This process was developed to analyze various overlay structures. HMA overlays over either asphalt pavement or jointed concrete pavement in all four major climatic zones are discussed in this dissertation. The results of this calculated mechanistic approach showed its ability to efficiently reproduce field observations of the growth, extent, and severity of reflection cracking. The most important contribution to crack growth was found to be thermal stress. The computer running time for a twenty-year prediction of a typical overlay was between one and four minutes.
Tsai, Fang-Ling
Blind Benchmark Calculations for Melt Spreading in the ECOSTAR Project
The Project ECOSTAR (5. EC Framework Programme) on Ex-Vessel Core Melt Stabilisation Research is oriented towards the analysis and mitigation of severe accident sequences that could occur in the ex-vessel phase of a postulated core melt accident. Spreading of the corium melt on the available basement surface is an important process, which defines the initial conditions for concrete attack and for the efficiency of cooling in case of water contact, respectively. The transfer and spreading of the melt on the basement is one of the major issues in ECOSTAR. This is addressed here by a spreading code benchmark involving a large-scale spreading experiment that is used for the validation of the existing spreading codes. The corium melt is simulated by a mixture of Al{sub 2}O{sub 3}, SiO{sub 2}, CaO and FeO with a sufficiently wide freezing interval. In the 3-dim benchmark test ECOKATS-1 170 litres of oxide melt are poured onto a 3 m by 4 m concrete surface with a low flow rate of about 2 l/s. From the results of an additional 2-dim channel experiment some basic rheological data (e.g. initial viscosity) are obtained in order to minimise the uncertainty in material properties of the melt. The participating spreading codes CORFLOW (Framatome ANP/FZK), LAVA (GRS), and THEMA (CEA) differ from each other by their focus of modelling and the assumptions made to simplify the relevant transport equations. In a first step both experiments (3-dim/2-dim) are calculated blindly by the participating codes. This serves for an overall assessment of the codes capabilities to predict the spreading of a melt with rather unknown material properties. In a second step the 3-dim experiment ECOKATS-1 is recalculated by the codes with the more precise knowledge of the rheological behaviour of the oxide melt in the 2-dim experiment. This, in addition, serves for the validation of the codes' capabilities to predict the spreading of a melt with well-known material properties. Based on the benchmark results and taking the specific validation process for each of the three codes applied into account, it is recommended that the spreading issue for reactor safety research be considered closed. (authors)
Spengler, C.; Allelein, H.J. [Gesellschaft fuer Anlagen- und Reaktorsicherheit, Schwertnergasse 1, 50667 Cologne (Germany); Foit, J.J.; Alsmeyer, H. [Forschungszentrum Karlsruhe, P.O. Box 36 40, 76021 Karlsruhe (Germany); Spindler, B.; Veteau, J.M. [CEA, 17, rue des Martyrs, 38054 Grenoble (France); Artnik, J.; Fischer, M. [Framatome ANP, P.O. Box 32 20, 91050 Erlangen (Germany)
Examination of cracked turbine discs from nuclear power plants
Investigations were performed on a cracked turbine disc from the Cooper Nuclear Power Station (BWR), and on two failed turbine discs from the Yankee-Rowe Nuclear Power Station (PWR). The Yankee-Rowe discs were subjected to SEM/EDAX, uniaxial tension tests, hardness testing, notch sensitivity tests, and environmental notched tensile tests. The results of this investigation support the model whereby the cracks initiated at startup of the turbine, probably from H/sub 2/S produced by hydrolysis of MoS/sub 2/, and grew at a rate consistent with published data for propagation of cracks in pure steam.
Czajkowski, C.J.; Weeks, J.R.
Shale oil cracking. 2. Effect on oil composition
Results from spectroscopic investigations are presented that demonstrate the effect of oil cracking on shale oil composition. Techniques used include infrared spectroscopy, capillary column gas chromatography/mass spectroscopy and /sup 13/C nuclear magnetic resonance. We show that cracking causes an increase in aromatic and alkene content of the oil. We compare our results for oils prepared in the laboratory with oils prepared in the TOSCO-II semi-works and in modified and true-in-situ combustion retorts. We demonstrate that the napthalene/2-methyl-naphthalene ratio is a good indicator of cracking conditions in an oil shale retort.
Burnham, A.K.; Sanborn, R.H.; Crawford, R.W.; Newton, J.C.; Happe, J.A.
Evaluation of Cracks in ABB HK Arc Chutes
The nuclear power industry has a number of medium voltage (5 Kv-15 Kv) ABB HK air-magnetic circuit breakers with cracks in various places on the ceramic liner plate and cold-molded asbestos portions of the arc chutes. These cracks may or may not be cosmetic. This "jump gap crack" issue has been discussed in several ABB circuit breaker users group meetings. Five utilities (Brunswick, Seabrook, TVA, Duke, and Vogtle) have previously expressed interest in this issue. The present ABB Quality Assurance Proced...
Strategies for planar crack propagation based on the concept of material forces
This paper presents a computational framework for the simulation of planar crack growth (including kinking) driven by "material forces". An evolution law for the crack tip position is formulated, which is shown to give rise to different propagation strategies ... Keywords: Configurational forces, Crack curving, Crack propagation
Jim Brouzoulis; Fredrik Larsson; Kenneth Runesson
Golden Spread Electric Cooperative, Inc. Smart Grid Project | Open Energy
Golden Spread Electric Cooperative, Inc. Golden Spread Electric Cooperative, Inc. Country United States Headquarters Location Amarillo, Texas Recovery Act Funding $19,995,000.00 Total Project Value $49,987,500.00 Coverage Area Coverage Map: Golden Spread Electric Cooperative, Inc. Smart Grid Project Coordinates 35.2219971°, -101.8312969° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[]}
Georgia Nonprofit Spreads the Word About Energy Efficiency | Department of
Georgia Nonprofit Spreads the Word About Energy Efficiency Georgia Nonprofit Spreads the Word About Energy Efficiency Georgia Nonprofit Spreads the Word About Energy Efficiency January 12, 2010 - 3:25pm Addthis Eric Barendsen Energy Technology Program Specialist, Office of Energy Efficiency and Renewable Energy At a time of strapped budgets, service organizations that find ways to save money through energy efficiency will more easily meet their fundraising goals. CHRIS Kids, an Atlanta-based nonprofit that provides housing to disadvantaged young people, is taking that idea to the next level. By upgrading its buildings with the latest in high-efficiency technologies, the group will reap the rewards of increased energy savings and, at the same time, teach the next generation about energy-efficiency technologies and behaviors.
The phenomenon of fragmentation and spreading of a high-speed flying object resembling a meteorite is studied experimentally and theoretically. Experimentally, a model made of graphite is launched in a ballistic range and is made to fragment and spread. The flow field produced by the cloud of the fragments is observed optically. The observed deceleration and spreading behavior is numerically reconstructed using computational-fluid-dynamic calculations, applying an improved meteoroid fragmentation theory. The existing meteoroid fragmentation theory is improved by introducing the hypothesis that the incubation process of the pressurized fluid permeating through the fragment precedes the splitting process. The incubation time is determined by the ratio of permeability of the fragment to the fluid's viscosity and is much longer than the time for splitting given by the existing theory. Agreement is obtained between the observed and calculated behavior of the fragment cloud by appropriately choosing this ratio.
Park, Chul [Department of Aerospace Engineering Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of); Brown, Jeffrey D. [ERC, Inc., Moffett Field, CA 94035 (United States)
North Carolina Nonprofit Helps Spread the Word About Weatherization |
Nonprofit Helps Spread the Word About Weatherization Nonprofit Helps Spread the Word About Weatherization North Carolina Nonprofit Helps Spread the Word About Weatherization September 3, 2010 - 10:00am Addthis Stephen Graff Former Writer & editor for Energy Empowers, EERE On Tuesday night, about 15 people gathered at the Lewisville Library in Winston-Salem, N.C., to hear three energy experts talk about how to tighten homes to save money on utility bills. Weather stripping, insulation and even planting trees were among the tips discussed. For two hours, people asked questions and took notes, learning as much as they could about how to weatherize their own homes. "Afterwards, the reaction from everyone was, 'wow that is a really great amount of information,'" says Terri LeGrand, executive director of Piedmont
North Carolina Nonprofit Helps Spread the Word About Weatherization North Carolina Nonprofit Helps Spread the Word About Weatherization North Carolina Nonprofit Helps Spread the Word About Weatherization September 3, 2010 - 10:00am Addthis Stephen Graff Former Writer & editor for Energy Empowers, EERE On Tuesday night, about 15 people gathered at the Lewisville Library in Winston-Salem, N.C., to hear three energy experts talk about how to tighten homes to save money on utility bills. Weather stripping, insulation and even planting trees were among the tips discussed. For two hours, people asked questions and took notes, learning as much as they could about how to weatherize their own homes. "Afterwards, the reaction from everyone was, 'wow that is a really great amount of information,'" says Terri LeGrand, executive director of Piedmont
EcoCar Students Spread the Word | Department of Energy
EcoCar Students Spread the Word EcoCar Students Spread the Word EcoCar Students Spread the Word June 16, 2011 - 11:34am Addthis Shannon Brescher Shea Communications Manager, Clean Cities Program "If you build it, they will come" is a mantra that might be well suited for rural sporting venues, but the organizers behind the EcoCAR competition realize that in the commercial sector, merely producing a finely tuned product often isn't enough to make it successful. That's why along with challenging students to re-engineer a donated vehicle to minimize gas consumption and emissions while maintaining consumer acceptability, they've made outreach and education key components of the competition. Whether they're speaking to policy makers or elementary school students, each of the teams have worked to convey the benefits of advanced technology
Environmentally Assisted Cracking of Ni-Base Alloys [Corrosion and
LWRs > Environmentally Assisted LWRs > Environmentally Assisted Cracking of Ni-Base Alloys Capabilities Materials Testing Environmentally Assisted Cracking (EAC) of Reactor Materials Corrosion Performance/Metal Dusting Overview Light Water Reactors Fatigue Testing of Carbon Steels and Low-Alloy Steels Environmentally Assisted Cracking of Ni-Base Alloys Irradiation-Induced Stress Corrosion Cracking of Austenitic Stainless Steels Steam Generator Tube Integrity Program Air Oxidation Kinetics for Zr-based Alloys Fossil Energy Fusion Energy Metal Dusting Publications List Irradiated Materials Steam Generator Tube Integrity Other Facilities Work with Argonne Contact us For Employees Site Map Help Join us on Facebook Follow us on Twitter NE on Flickr Corrosion and Mechanics of Materials Light Water Reactors
3D Characterization and Modeling of Fatigue Cracks
The HEDM and CT are performed with high energy x-rays at the Advanced Photon Source (APS). One set of LSHR specimens has small cracks on the order of�...
Cracked shaft detection and diagnostics: A literature review
ABSTRACT�Cracks in shafts have long been identified as factors limiting the safe and reliable operation of turbomachines. They can sometimes result in catastrophic failure of equipment (rotor bursts) and, more often, in costly process upsets, repairs and premature scrapping and replacement of equipment. Cracked shafts still pose a significant and real threat to equipment in spite of the great advances made in the areas of metallurgy, manufacturing and design. In the past two decades, much research and many resources have gone into developing various on-line and off-line diagnostic techniques to effectively detect cracks before they cause serious damage. Because of the enormous amount of ongoing research in this area (more than 500 technical papers have been published in English alone in the past 30 years), there is a real need to periodically condense and summarize the information. This paper reviews literature on cracked shaft detection and diagnostics published after 1990.
Giridhar Sabnavis; R. Gordon Kirk; Mary Kasarda; Dane Quinn; Giridhar Sabnavis; R. Gordon Kirk; Mary Kasarda; Dane Quinn
Process to minimize cracking of pyrolytic carbon coatings
Carbon-coated microspheroids useful as fuels in nuclear reactors are produced with a low percentage of cracked coatings and are imparted increased strength and mechanical stability characteristics by annealing immediately after the carbon coating processes.
Lackey, Jr., Walter J. (Oak Ridge, TN); Sease, John D. (Knoxville, TN)
Effect of Oxygen Potential on Crack Growth in Alloy 617
Static crack growth rate increases from 4 x 10-9 m/sec to 4 x 10-8 m/sec when the oxygen concentration decreases from .001 to .0000001 atm. Proceedings�...
SLAC National Accelerator Laboratory - SLAC Research Cracks Puzzle...
Press Release Archive SLAC Research Cracks Puzzle of Enzyme Critical to Food Supply November 17, 2011 Menlo Park, Calif. - If we could make plant food from nitrogen the way nature...
Crack coalescence in rock-like material under cycling loading
A total of 170 tests (68 tests for monotonic loading, 102 tests for cyclic loading) have been performed to investigate crack initiation, propagation and coalescence. The specimens have two pre-existing flaws which are ...
Ko, Tae Young, 1973-
Evaluation of Stress Corrosion Cracking Susceptibility of Drill Pipe ...
G-105 and S-135 grades of drill pipe steels have been used to study the effect of temperature and solution chemistry on the stress corrosion cracking behavior of�...
Irradiation-Induced Stress Corrosion Cracking of Austenitic Stainless
Environmentally Assisted Environmentally Assisted Cracking of Ni-Base Alloys Capabilities Materials Testing Environmentally Assisted Cracking (EAC) of Reactor Materials Corrosion Performance/Metal Dusting Overview Light Water Reactors Fatigue Testing of Carbon Steels and Low-Alloy Steels Environmentally Assisted Cracking of Ni-Base Alloys Irradiation-Induced Stress Corrosion Cracking of Austenitic Stainless Steels Steam Generator Tube Integrity Program Air Oxidation Kinetics for Zr-based Alloys Fossil Energy Fusion Energy Metal Dusting Publications List Irradiated Materials Steam Generator Tube Integrity Other Facilities Work with Argonne Contact us For Employees Site Map Help Join us on Facebook Follow us on Twitter NE on Flickr Corrosion and Mechanics of Materials Light Water Reactors Bookmark and Share
Temperature dependence of the intrinsic small fatigue crack growth behavior in Ni-base superalloys based on measurement of crack closure
The effect of temperature on the small fatigue crack growth behavior of a single crystal and directionally solidified Ni-base superalloys was investigated at temperatures between 873 to 1,123 K by measuring the crack closure. The results were also compared with those of the physically long crack. It was found that the propagation resistance and the fatigue threshold of the long cracks increased with temperature in all the materials. The long crack growth rates at three temperatures were approximately represented by an unique curve, after taking account of crack closure level and elastic modulus. In contrast, the small crack growth resistance decreased with temperature even when the crack closure phenomenon was taken into consideration. Furthermore, the small fatigue cracks exhibited considerably higher growth rates than the long cracks at a given effective stress intensity factor range and also grew under effective stress intensity factor ranges below the long crack threshold. The factors responsible for the lack of similitude in propagation rates between small and long cracks were also discussed, based on these observations and the chemical analysis near the crack tip using the electron probe microanalyzer.
Okazaki, M.; Yamada, H. [Nagaoka Univ. of Technology (Japan). Dept. of Mechanical Engineering; Nohmi, S. [Kawasaki Heavy Industries Co. Ltd., Akashi (Japan)
Nucleation and growth of cracks in vitreous-bonded aluminum oxide at elevated temperatures
The nucleation and growth of cracks was studied at elevated temperatures on a grade of vitreous-bonded aluminium oxide that contained approx. =8 vol% glass at the grain boundaries. Cracks were observed to nucleate within the vitreous phase, close to the tensile surface of the flexural test specimens used in these experiments. Crack nucleation occurred at a strain of approx. =0.08% to 0.12% which corresponded to a crack nucleation time of approx. =35% of the time to failure by creep rupture. Once nucleated, cracks propagated along grain boundaries, as long as the stress for crack propagation was maintained. The crack velocity for cracks that were nucleated by the creep process was found to be linearly proportional to the apparent stress intensity factor, whereas for cracks that were nucleated by indentation, the crack velocity was proportional to the fourth power of the apparent stress intensity factor.
Jakus, K.; Wiederhorn, S.M.; Hockey, B.J.
Crack reconstruction using a level-set strategy
We present a level-set based technique to recover key characteristics of a defect or crack (e.g. location, length and shape) in a two-dimensional material from boundary electrical measurements. The key feature of this work is to extend the usual level-set ... Keywords: 02.30.Zz, 41.20.Cv, 42.30.Wb, Crack reconstruction, Electrical impedance tomography, Level-sets
Diego �lvarez; Oliver Dorn; Natalia Irishina; Miguel Moscoso
Reliability Centered Lifetime Prediction of Environmentally Assisted Cracking
This report describes the results of joint research sponsored by EPRI in cooperation with Tohoku University and a number of Japanese organizations to address the issue of environmentally assisted cracking (EAC) in boiling water reactors (BWRs) and pressurized water reactors (PWRs). The term EAC includes intergranular stress corrosion cracking and corrosion fatigue. The goal of this project was to develop a fundamental understanding of processes controlling EAC of stainless steels and nickel-base alloys i...
Large energy-spread beam diagnostics through quadrupole scans
The Facility for Advanced Accelerator and Experimental Tests (FACET) is a new user facility at the SLAC National Accelerator Laboratory, servicing next-generation accelerator experiments. The 1.5% RMS energy spread of the FACET beam causes large chromatic aberrations in optics. These aberrations necessitate updated quadrupole scan fits to remain accurate.
Frederico, Joel; Adli, Erik; Hogan, Mark; Raubenheimer, Tor [SLAC National Accelerator Laboratory (United States)
Low energy spread ion source with a coaxial magnetic filter
Multicusp ion sources are capable of producing ions with low axial energy spread which are necessary in applications such as ion projection lithography (IPL) and radioactive ion beam production. The addition of a radially extending magnetic filter consisting of a pair of permanent magnets to the multicusp source reduces the energy spread considerably due to the improvement in the uniformity of the axial plasma potential distribution in the discharge region. A coaxial multicusp ion source designed to further reduce the energy spread utilizes a cylindrical magnetic filter to achieve a more uniform axial plasma potential distribution. The coaxial magnetic filter divides the source chamber into an outer annular discharge region in which the plasma is produced and a coaxial inner ion extraction region into which the ions radially diffuse but from which ionizing electrons are excluded. The energy spread in the coaxial source has been measured to be 0.6 eV. Unlike other ion sources, the coaxial source has the capability of adjusting the radial plasma potential distribution and therefore the transverse ion temperature (or beam emittance).
Leung, Ka-Ngo (Hercules, CA); Lee, Yung-Hee Yvette (Berkeley, CA)
Strengthening, Crack Arrest And Multiple Cracking In Brittle Materials Using Residual Stresses.
Embodiments include a method for forming a glass which displays visible cracking prior to failure when subjected to predetermined stress level that is greater than a predetermined minimum stress level and less than a failure stress level. The method includes determining a critical flaw size in the glass and introducing a residual stress profile to the glass so that a plurality of visible cracks are formed prior to failure when the glass is subjected to a stress that is greater than the minimum stress level and lower than the critical stress. One method for forming the residual stress profile includes performing a first ion exchange so that a first plurality of ions of a first element in the glass are exchanged with a second plurality of ions of a second element that have a larger volume than the first ions. A second ion exchange is also performed so that a plurality of the second ions in the glass are exchanged back to ions of the first element.
Green, David J. (State College, PA); Sglavo, Vincenzo M. (Roncegno, IT); Tandon, Rajan (Fremont, CA)
Stress corrosion cracking of austenitic stainless steel core internal welds.
Microstructural analyses by several advanced metallographic techniques were conducted on austenitic stainless steel mockup and core shroud welds that had cracked in boiling water reactors. Contrary to previous beliefs, heat-affected zones of the cracked Type 304L, as well as 304 SS core shroud welds and mockup shielded-metal-arc welds, were free of grain-boundary carbides, which shows that core shroud failure cannot be explained by classical intergranular stress corrosion cracking. Neither martensite nor delta-ferrite films were present on the grain boundaries. However, as a result of exposure to welding fumes, the heat-affected zones of the core shroud welds were significantly contaminated by oxygen and fluorine, which migrate to grain boundaries. Significant oxygen contamination seems to promote fluorine contamination and suppress thermal sensitization. Results of slow-strain-rate tensile tests also indicate that fluorine exacerbates the susceptibility of irradiated steels to intergranular stress corrosion cracking. These observations, combined with previous reports on the strong influence of weld flux, indicate that oxygen and fluorine contamination and fluorine-catalyzed stress corrosion play a major role in cracking of core shroud welds.
Chung, H. M.; Park, J.-H.; Ruther, W. E.; Sanecki, J. E.; Strain, R. V.; Zaluzec, N. J.
Crack Surface Roughness in Three-Dimensional Random Fuse Networks
Using large system sizes with extensive statistical sampling, we analyze the scaling properties of crack roughness and damage profiles in the three-dimensional random fuse model. The analysis of damage profiles indicates that damage accumulates in a diffusive manner up to the peak load, and localization sets in abruptly at the peak load starting from a uniform damage landscape. The global crack width scales as $W \\sim L^{0.5}$ and is consistent with the scaling of localization length $\\xi \\sim L^{0.5}$ used in the data collapse of damage profiles in the post-peak regime. This consistency between the global crack roughness exponent and the post-peak damage profile localization length supports the idea that the post-peak damage profile is predominantly due to the localization produced by the catastrophic failure, which at the same time results in the formation of the final crack. Finally, the crack width distributions can be collapsed for different system sizes and follow a log-normal distribution.
Nukala, Phani K [ORNL; Zapperi, Stefano [University of La Sapienza, Rome; Simunovic, Srdjan [ORNL
Radioactive wastes are confined in 49 underground storage tanks at the Savannah River Site. The tanks are examined by ultrasonic (UT) methods for thinning, pitting, and stress corrosion cracking in order to assess fitness-for-service. During an inspection in 2002, ten cracks were identified on one of the tanks. Given the location of the cracks (i.e., adjacent to welds, weld attachments, and weld repairs), fabrication details (e.g., this tank was not stress-relieved), and the service history the degradation mechanism was stress corrosion cracking. Crack instability calculations utilizing API-579 guidance were performed to show that the combination of expected future service condition hydrostatic and weld residual stresses do not drive any of the identified cracks to instability. The cracks were re-inspected in 2007 to determine if crack growth had occurred. During this re-examination, one indication that was initially reported as a 'possible perpendicular crack <25% through wall' in 2002, was clearly shown not to be a crack. Additionally, examination of a new area immediately adjacent to other cracks along a vertical weld revealed three new cracks. It is not known when these new cracks formed as they could very well have been present in 2002 as well. Therefore, a total of twelve cracks were evaluated during the re-examination. Comparison of the crack lengths measured in 2002 and 2007 revealed that crack growth had occurred in four of the nine previously measured cracks. The crack length extension ranged from 0.25 to 1.8 inches. However, in all cases the cracks still remained within the residual stress zone (i.e., within two to three inches of the weld). The impact of the cracks that grew on the future service of Tank 15 was re-assessed. API-579 crack instability calculations were again performed, based on expected future service conditions and trended crack growth rates for the future tank service cycle. The analysis showed that the combined hydrostatic and weld residual stresses do not drive the identified cracks to instability. This tank expected to be decommissioned in the near future. However, if these plans are delayed, it was recommended that a third examination of selected cracks in the tank be performed in 2014.
Wiersma, B; James Elder, J; Rodney Vandekamp, R; Charles Mckeel, C
Stress corrosion cracking of candidate waste container materials
Six alloys have been selected as candidate container materials for the storage of high-level nuclear waste at the proposed Yucca Mountain site in Nevada. These materials are Type 304L stainless steel (SS), Type 316L SS, Incology 825, P-deoxidized Cu, Cu-30%Ni, and Cu-7% Al. The present program has been initiated to determine whether any of these materials can survive for 300 years in the site environment without developing through-wall stress corrosion cracks, and to assess the relative resistance of these materials to stress corrosion cracking (SCC). A series of slow-strain-rate tests (SSRTs) in simulated Well J-13 water which is representative of the groundwater present at the Yucca Mountain site has been completed, and crack-growth-rate (CGR) tests are also being conducted under the same environmental conditions. 13 refs., 60 figs., 22 tabs.
Maiya, P.S.; Soppet, W.K.; Park, J.Y.; Kassner, T.F.; Shack, W.J.; Diercks, D.R.
Cracking Condition of Cohesionless Porous Materials in Drying Processes
The invasion of air into porous systems in drying processes is often localized in soft materials, such as colloidal suspensions and granular pastes, and it typically develops in the form of cracks before ordinary drying begins. To investigate such processes, we construct an invasion percolation model on a deformable lattice for cohesionless elastic systems, and with this model we derive the condition under which cracking occurs. A Griffith-like condition characterized by a dimensionless parameter is proposed, and its validity is checked numerically. This condition indicates that the ease with which cracking occurs increases as the particles composing the material become smaller, as the rigidity of the system increases, and as the degree of heterogeneity characterizing the drying processes decreases.
So Kitsunezaki
Cracking a Cold Case and Enduring Mystery | Department of Energy
Cracking a Cold Case and Enduring Mystery Cracking a Cold Case and Enduring Mystery Cracking a Cold Case and Enduring Mystery July 1, 2013 - 3:04pm Addthis Chris Brandon of the ROMACONS project collects a sample of ancient Roman concrete drilled from a breakwater in Pozzuoli Bay, near Naples, Italy. The breakwater dates back to roughly 37 B.C. | Photo courtesy of J.P. Oleson. Chris Brandon of the ROMACONS project collects a sample of ancient Roman concrete drilled from a breakwater in Pozzuoli Bay, near Naples, Italy. The breakwater dates back to roughly 37 B.C. | Photo courtesy of J.P. Oleson. Charles Rousseaux Charles Rousseaux Senior Writer, Office of Science What are the key facts? Modern concrete buildings -- most made with Portland cement -- are built to last for a hundred or so years. But Roman concrete has withstood
Characterization of geothermal reservoir crack patterns using shear-wave
geothermal reservoir crack patterns using shear-wave geothermal reservoir crack patterns using shear-wave splitting Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Journal Article: Characterization of geothermal reservoir crack patterns using shear-wave splitting Details Activities (1) Areas (1) Regions (0) Abstract: Microearthquakes recorded by a downhole, three-component seismic network deployed around the Coso, California, geothermal reservoir since 1992 display distinctive shear-wave splitting and clear polarization directions. From the polarizations the authors estimated three predominant subsurface fracture directions, and from the time delays of the split waves they determined tomographically the 3-D fracture density distribution in the reservoir. Author(s): Lou, M.; Rial, J.A. Published: Geophysics, 3/1/1997
Shear-wave splitting and reservoir crack characterization: the Coso
Shear-wave splitting and reservoir crack characterization: the Coso Shear-wave splitting and reservoir crack characterization: the Coso geothermal field Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Journal Article: Shear-wave splitting and reservoir crack characterization: the Coso geothermal field Details Activities (1) Areas (1) Regions (0) Abstract: This paper aims to improve current understanding of the subsurface fracture system in the Coso geothermal field, located in east-central California. The Coso reservoir is in active economic development, so that knowledge of the subsurface fracture system is of vital importance for an accurate evaluation of its geothermal potential and day-to-day production. To detect the geometry and density of fracture systems we applied the shear-wave splitting technique to a large number of
Dynamic crack initiation toughness : experiments and peridynamic modeling.
This is a dissertation on research conducted studying the dynamic crack initiation toughness of a 4340 steel. Researchers have been conducting experimental testing of dynamic crack initiation toughness, K{sub Ic}, for many years, using many experimental techniques with vastly different trends in the results when reporting K{sub Ic} as a function of loading rate. The dissertation describes a novel experimental technique for measuring K{sub Ic} in metals using the Kolsky bar. The method borrows from improvements made in recent years in traditional Kolsky bar testing by using pulse shaping techniques to ensure a constant loading rate applied to the sample before crack initiation. Dynamic crack initiation measurements were reported on a 4340 steel at two different loading rates. The steel was shown to exhibit a rate dependence, with the recorded values of K{sub Ic} being much higher at the higher loading rate. Using the knowledge of this rate dependence as a motivation in attempting to model the fracture events, a viscoplastic constitutive model was implemented into a peridynamic computational mechanics code. Peridynamics is a newly developed theory in solid mechanics that replaces the classical partial differential equations of motion with integral-differential equations which do not require the existence of spatial derivatives in the displacement field. This allows for the straightforward modeling of unguided crack initiation and growth. To date, peridynamic implementations have used severely restricted constitutive models. This research represents the first implementation of a complex material model and its validation. After showing results comparing deformations to experimental Taylor anvil impact for the viscoplastic material model, a novel failure criterion is introduced to model the dynamic crack initiation toughness experiments. The failure model is based on an energy criterion and uses the K{sub Ic} values recorded experimentally as an input. The failure model is then validated against one class of problems showing good agreement with experimental results.
Foster, John T.
Weld solidification cracking in 304 to 204L stainless steel
A series of annulus welds were made between 304 and 304L stainless steel coaxial tubes using both pulsed laser beam welding (LBW) and pulsed gas tungsten arc welding (GTAW). In this application, a change in process from pulsed LBW to pulsed gas tungsten arc welding was proposed to limit the possibility of weld solidification cracking since weldability diagrams developed for GTAW display a greater range of compositions that are not crack susceptible relative to those developed for pulsed LBW. Contrary to the predictions of the GTAW weldability diagram, cracking was found.This result was rationalized in terms of the more rapid solidification rate of the pulsed gas tungsten arc welds. In addition, for the pulsed LBW conditions, the material compositions were predicted to be, by themselves, 'weldable' according to the pulsed LBW weldability diagram. However, the composition range along the tie line connecting the two compositions passed through the crack susceptible range. Microstructurally, the primary solidification mode (PSM) of the material processed with higher power LBW was determined to be austenite (A), while solidification mode of the materials processed with lower power LBW apparently exhibited a dual PSM of both austenite (A) and ferrite-austenite (FA) within the same weld. The materials processed by pulsed GTAW showed mostly primary austenite solidification, with some regions of either primary austenite-second phase ferrite (AF) solidification or primary ferrite-second phase austenite (FA) solidification. This work demonstrates that variations in crack susceptibility may be realized when welding different heats of 'weldable' materials together, and that slight variations in processing can also contribute to crack susceptibility.
Hochanadel, Patrick W [Los Alamos National Laboratory; Lienert, Thomas J [Los Alamos National Laboratory; Martinez, Jesse N [Los Alamos National Laboratory; Johnson, Matthew Q [Los Alamos National Laboratory
Weld solidification cracking in 304 to 304L stainless steel
A series of annulus welds were made between 304 and 304L stainless steel coaxial tubes using both pulsed laser beam welding (LBW) and pulsed gas tungsten arc welding (GTAW). In this application, a change in process from pulsed LBW to pulsed gas tungsten arc welding was proposed to limit the possibility of weld solidification cracking since weldability diagrams developed for GTAW display a greater range of compositions that are not crack susceptible relative to those developed for pulsed LBW. Contrary to the predictions of the GTAW weldability diagram, cracking was found. This result was rationalized in terms of the more rapid solidification rate of the pulsed gas tungsten arc welds. In addition, for the pulsed LBW conditions, the material compositions were predicted to be, by themselves, 'weldable' according to the pulsed LBW weldability diagram. However, the composition range along the tie line connecting the two compositions passed through the crack susceptible range. Microstructurally, the primary solidification mode (PSM) of the material processed with higher power LBW was determined to be austenite (A), while solidification mode of the materials processed with lower power LBW apparently exhibited a dual PSM of both austenite (A) and ferrite-austenite (FA) within the same weld. The materials processed by pulsed GT A W showed mostly primary austenite solidification, with some regions of either primary austenite-second phase ferrite (AF) solidification or primary ferrite-second phase austenite (FA) solidification. This work demonstrates that variations in crack susceptibility may be realized when welding different heats of 'weldable' materials together, and that slight variations in processing can also contribute to crack susceptibility.
Hochanadel, Patrick W [Los Alamos National Laboratory; Lienert, Thomas J [Los Alamos National Laboratory; Martinez, Jesse N [Los Alamos National Laboratory; Martinez, Raymond J [Los Alamos National Laboratory; Johnson, Matthew Q [Los Alamos National Laboratory
Radioactive wastes are confined in 49 underground storage tanks at the Savannah River Site. The tanks are examined by ultrasonic (UT) methods for thinning, pitting, and stress corrosion cracking in order to assess fitness-for-service. During an inspection in 2002, ten cracks were identified on one of the tanks. Given the location of the cracks (i.e., adjacent to welds, weld attachments, and weld repairs), fabrication details (e.g., this tank was not stress-relieved), and the service history the degradation mechanism was stress corrosion cracking. Crack instability calculations utilizing API-579 guidance were performed to show that the combination of expected future service condition hydrostatic and weld residual stresses do not drive any of the identified cracks to instability. The cracks were re-inspected in 2007 to determine if crack growth had occurred. During this re-examination, one indication that was initially reported as a 'possible perpendicular crack API-579 crack instability calculations were again performed, based on expected future service conditions and trended crack growth rates for the future tank service cycle. The analysis showed that the combined hydrostatic and weld residual stresses do not drive the identified cracks to instability. This tank expected to be decommissioned in the near future. However, if these plans are delayed, it was recommended that a third examination of selected cracks in the tank be performed in 2014.
Hydrogen sulfide stress corrosion cracking in materials for geothermal power
Studies to evaluate the performance of alloys used in geothermal power systems are reported. Alloys which are commercially available and those which have modified metallurgical structures and/or composition modifications were tested to determine the corrosive effects of the H/sub 2/S and thermal environments in geothermal fluids. Hydrogen embrittlement and sulfide stress corrosion cracking were tested. Test results showing the effects of alloy composition, tempering temperatures, fluid temperature and salt content, and ageing on sulfide stress cracking are tabulated. (LCL)
Hehemann, R.F.; Troiano, A.R.; Abu-Khater, B.; Ferrigno, S.
Thermal stress cracking and enhancement of heat extraction from fractured geothermal reservoirs
The effects of thermal stress cracking, upon heat extraction were studied. Very fundamental approximate analyses were performed to elucidate the mechanics of thermal stress cracking, and the main results are summarized.
Murphy, H.D.
Crack Growth in Solid Oxide Fuel Cell Materials: From Discrete to Continuum Damage Modeling
This paper addresses the cracking problem of glass and ceramic materials used in solid oxide fuel cells (SOFCs). Analyses of an internal crack and of an interface crack between dissimilar materials were conducted using a modified boundary layer modeling approach. In this approach, fracture is allowed to occur in a small process window situated at an initial crack tip. Elastic displacement crack-tip fields are prescribed as remote boundary conditions. Crack propagation was first modeled discretely. Next, a continuum damage mechanics (CDM) model for brittle materials was developed to capture damage and crack growth in the process window. In particular, the damage model was applied to a glass-ceramic material that had been developed in-house for sealing purposes. Discrete and continuum damage solutions were then compared. Finally, the CDM model was used to determine the crack propagation direction as a function of a mode mixity measure.
Nguyen, Ba Nghiep; Koeppel, Brian J.; Ahzi, Said; Khaleel, Mohammad A.; Singh, Prabhakar
A New Approach to Estimate Directional Spreading Parameters of a Cosine-2s Model
For accurate and consistent estimates of the directional spreading parameter and mean wave direction of directional seas based on a cosine-2s directional spreading model, a new approach is proposed, employing a maximum likelihood method (MLM) to ...
Shaosong Zhang; Jun Zhang
Measuring the Ensemble Spread�Error Relationship with a Probabilistic Approach: Stochastic Ensemble Results
One widely accepted measure of the utility of ensemble prediction systems is the relationship between ensemble spread and deterministic forecast accuracy. Unfortunately, this relationship is often characterized by spread�error linear correlations,...
Eric P. Grimit; Clifford F. Mass
Laboratory And Field Investigations To Address Erosion, Volume Change And Desiccation Cracking Of Compost Amended Expansive Subsoils.
??Puppala, Anand Desiccations cracks are formed during drying process of fine grained cohesive soils in summer and these cracks often appear on unpaved subgrades due� (more)
Intharasombat, Napat
Influence of p-method finite element parameters on predictions of crack front geometry
The effect of various p-method finite element model parameters on the prediction of planar crack front geometry in three dimensional structures is evaluated. An automatic crack growth method was developed using the commercial software StressCheck coupled ... Keywords: ?, Corner crack, Crack front, Finite element, Mesh, Stress intensity factor, a, b, b/a, c, ctrat, ipr, m, mrat, p-method, trans
Diane Wowk, Kyle Gamble, Ross Underhill
Status Report on Studies of Recovery Boiler Composite Floor Tube Cracking
likelihood of cracking. This report is the latest in a series of progress reports presented on this project.
Eng, P.; Frederick, L.A.; Hoffmann, C.M.; Keiser, J.R.; Mahmood, J.; Maziasz, P.J.; Prescott, R.; Sarma, G.B.; Singbeil, D.L.; Singh, P.M.; Swindeman, R.W.; Wang, X.-L.
Effect of Specimen Size on the Crack Growth Rate Behavior of Irradiated Type 304 Stainless Steel
BackgroundCracks in actual plant components are mainly under plane strain. In order to generate relevant crack growth rate data in the laboratory, specimens where most of the crack front is under plane strain should be used. Since the ASTM E399 size criterion for linear elastic plane-strain fracture toughness is probably conservative, it seems appropriate to also apply it to SCC tests. However, in stress corrosion crack growth rate (CGR) tests on austenitic stainless ...
How Tough is Human Cortical Bone? In-Situ Measurements on Realistically Short Cracks
Bone is more difficult to break than to split. Although this is well known, and many studies exist on the behavior of long cracks in bone, there is a need for data on the orientation-dependent crack-growth resistance behavior of human cortical bone which accurately assesses its toughness at appropriate size-scales. Here we use in-situ mechanical testing in the scanning electron microscope and x-ray computed tomography to examine how physiologically-pertinent short (<600 mu m) cracks propagate in both the transverse and longitudinal orientations in cortical bone, using both crack-deflection/twist mechanics and nonlinear-elastic fracture mechanics to determine crack-resistance curves. We find that after only 500 mu m of cracking, the driving force for crack propagation was more than five times higher in the transverse (breaking) direction than in the longitudinal (splitting) direction due to major crack deflections/twists principally at cement sheathes. Indeed, our results show that the true transverse toughness of cortical bone is far higher than previously reported. However, the toughness in the longitudinal orientation, where cracks tend to follow the cement lines, is quite low at these small crack sizes; it is only when cracks become several millimeters in length that bridging mechanisms can develop leading to the (larger-crack) toughnesses generally quoted for bone.
Ritchie, Robert O; Koester, K. J.; Ager III, J. W.; Ritchie, R.O.
Early Development Of Stress Corrosion Cracks At The Grain Scale: Incomplete Random Tessellation Model
Early Development Of Stress Corrosion Cracks At The Grain Scale: Incomplete Random Tessellation is needed to quantify those effects more accurately. 1 INTRODUCTION Intergranular stress corrosion cracking to the dependence of microscopic stress fields at crack tips on the random orientation of neighboring grains
Cizelj, Leon
Age-based preventive maintenance for passive components submitted to stress corrosion cracking
This paper deals with an age-based preventive maintenance for critical systems or structures subject to a gradual degradation phenomenon such as stress corrosion cracking. We analyze a system subjected to different cracks. A crack can be only detected ... Keywords: Age-based maintenance, Counting processes, Gamma process, Non-homogeneous Poisson process, SCC models
I. T. Castro; Anne Barros; Antoine Grall
Permeability and elastic properties of cracked glass under pressure A. OugierSimonin,1
on slow crack growth and stress corrosion processes [Wiederhorn, 1966; Anderson and Grew, 1977; Atkinson for independent controls of the confining pressure, the axial stress, and pore pressure. We produced cracks, to our knowledge, none con- sidered crack evolution under compressive stress. Some of this work explored
Fortin, Jérôme
Uplift Pressures in Cracks in Concrete Gravity Dams--An Experimental Study: Volume 8
Uplift pressure distribution in cracks in concrete dams is affected by a combination of several factors, such as crack properties, drain dimensions, and the type of flow in the crack. This study shows that most uplift pressure distributions can be controlled using a vertical drain system with diameters from two to four inches and spacing of about ten feet.
Ductile Fracture Handbook, Volume 1: Circumferential Throughwall Cracks
Over the past 10 years, the focus of fracture research related to nuclear power plants has shifted from brittle fractures to fractures of steels used for piping and vessels. This handbook developed by EPRI and Novetech Corporation is the first single-source document containing formulas for evaluating throughwall cracks in these tough ductile steels.
A computational study of the time dependent crack growth process
Universal studies of creep crack growth for (1) constant load and (2) variable load cases are presented. Results of the constant load cases is compared to experiment. The behavior of displacements and integral creep for fracture parameters are discussed for both load cases. The need for using a constitutive law which can handle cyclic creep is discussed.
Brust, F.W.; Krishnaswamy, P.
Catalytic cracking. (Latest citations from the Compendex database). Published Search
The bibliography contains citations concerning applications of catalytic cracking processes in fluidized bed systems, moving beds, refineries, vacuum distillations, and reformers. Design aspects, modeling, control systems, and operating procedures are also discussed. (Contains a minimum of 149 citations and includes a subject term index and title list.)
Not Available
Incipient Crack Detection in Composite Wind Turbine Blades
This paper presents some analysis results for incipient crack detection in a 9-meter CX-100 wind turbine blade that underwent fatigue loading to failure. The blade was manufactured to standard specifications, and it underwent harmonic excitation at its first resonance using a hydraulically-actuated excitation system until reaching catastrophic failure. This work investigates the ability of an ultrasonic guided wave approach to detect incipient damage prior to the surfacing of a visible, catastrophic crack. The blade was instrumented with piezoelectric transducers, which were used in an active, pitchcatch mode with guided waves over a range of excitation frequencies. The performance results in detecting incipient crack formation in the fiberglass skin of the blade is assessed over the range of frequencies in order to determine the point at which the incipient crack became detectable. Higher excitation frequencies provide consistent results for paths along the rotor blade's carbon fiber spar cap, but performance falls off with increasing excitation frequencies for paths off of the spar cap. Lower excitation frequencies provide more consistent performance across all sensor paths.
Taylor, Stuart G. [Los Alamos National Laboratory; Choi, Mijin [Chonbuk National University, Korea; Jeong, Hyomi [Chonbuk National University, Korea; Jang, Jae Kyeong [Chonbuk National University, Korea; Park, Gyuhae [Chonnam National University, Korea; Farinholt, Kevin [Commonwealth Center for Advanced Manufacturing, VA; Farrar, Charles R. [Los Alamos National Laboratory; Ammerman, Curtt N. [Los Alamos National Laboratory; Todd, Michael D. [Los Alamos National Laboratory; Lee, Jung-Ryul [Chonbuk National University, Korea
Fatigue crack growth estimation by relevance vector machine
The investigation of damage propagation mechanisms on a selected safety-critical component or structure requires the quantification of its remaining useful life (RUL) to verify until when it can continue performing the required function. In this work, ... Keywords: Bayesian techniques, Fatigue crack growth, Prognostics, Relevance vector machine, Residual useful life, Support vector machine
Enrico Zio; Francesco Di Maio
Solvent control of crack dynamics in a reversible hydrogel
The resistance to fracture of reversible biopolymer hydrogels is an important control factor of the cutting/slicing and eating characteristics of food gels. It is also critical for their utilization in tissue engineering, for which mechanical protection of encapsulated components is needed. Its dependence on loading rate and, recently, on the density and strength of cross-links has been investigated. But no attention was paid so far to solvent nor to environment effects. Here we report a systematic study of crack dynamics in gels of gelatin in water/glycerol mixtures. We show on this model system that: (i) increasing solvent viscosity slows down cracks; (ii) soaking with solvent increases markedly gel fragility; (iii) tuning the viscosity of the (miscible) environmental liquid affects crack propagation via diffusive invasion of the crack tip vicinity. The results point toward the fact that fracture occurs by viscoplastic chain pull-out. This mechanism, as well as the related phenomenology, should be common to all reversibly cross-linked (physical) gels.
Tristan Baumberger; Christiane Caroli; David Martina
Method of making crack-free zirconium hydride
Crack-free hydrides of zirconium and zirconium-uranium alloys are produced by alloying the zirconium or zirconium-uranium alloy with beryllium, or nickel, or beryllium and scandium, or nickel and scandium, or beryllium and nickel, or beryllium, nickel and scandium and thereafter hydriding.
Sullivan, Richard W. (Denver, CO)
How to Measure the Spreading Width of Superdeformed Nuclei
A new expression for the branching ratio for the decay via the E1 process in the normal-deformed band of superdeformed nuclei is given within a simple two-level model. Using this expression, the spreading or tunneling width {gamma}{down_arrow} for superdeformed decay can be expressed entirely in terms of experimentally known quantities. We show how to determine the tunneling matrix element V from the measured value of {gamma}{down_arrow} and a statistical model of the energy levels.
Cardamone, D.M.; Stafford, C.A.; Barrett, B.R. [Department of Physics, University of Arizona, Tucson, AZ 85721 (United States)
Momentum spread in a relativistic electron beam in an undulator
The motion of the relativistic electron beam in the spatially periodic magnetic field of an undulator has been considered taking into account the effect of the incoherent field of the spontaneous undulator radiation on the motion of the electrons. An expression for the rms momentum of the electrons has been obtained. It has been shown that the momentum spread in the ultrarelativistic electron beam increases in the spontaneous incoherent emission mode. Conditions for the self-amplification of the spontaneous undulator radiation in ultrashort-wavelength free-electron lasers have been discussed.
Ognivenko, V. V., E-mail: firstname.lastname@example.com [National Science Center Kharkov Institute of Physics and Technology (Ukraine)
Airborne spread of foot-and-mouth disease - model intercomparison
Foot-and-mouth disease is a highly infectious vesicular disease of cloven-hoofed animals caused by foot-and-mouth disease virus. It spreads by direct contact between animals, by animal products (milk, meat and semen), by mechanical transfer on people or fomites and by the airborne route - with the relative importance of each mechanism depending on the particular outbreak characteristics. Over the years a number of workers have developed or adapted atmospheric dispersion models to assess the risk of foot-and-mouth disease virus spread through the air. Six of these models were compared at a workshop hosted by the Institute for Animal Health/Met Office during 2008. A number of key issues emerged from the workshop and subsequent modelling work: (1) in general all of the models predicted similar directions for 'at risk' livestock with much of the remaining differences strongly related to differences in the meteorological data used; (2) determination of an accurate sequence of events is highly important, especially if the meteorological conditions vary substantially during the virus emission period; and (3) differences in assumptions made about virus release, environmental fate, and subsequent infection can substantially modify the size and location of the downwind risk area. Close relationships have now been established between participants, which in the event of an outbreak of disease could be readily activated to supply advice or modelling support.
Gloster, J; Jones, A; Redington, A; Burgin, L; Sorensen, J H; Turner, R; Dillon, M; Hullinger, P; Simpson, M; Astrup, P; Garner, G; Stewart, P; D'Amours, R; Sellers, R; Paton, D
Bone is more difficult to break than to split. Although this is well known, and many studies exist on the behavior of long cracks in bone, there is a need for data on the orientation-dependent crack-growth resistance behavior of human cortical bone which accurately assesses its toughness at appropriate size-scales. Here we use in-situ mechanical testing in the scanning electron microscope and x-ray computed tomography to examine how physiologically-pertinent short (propagate in both the transverse and longitudinal orientations in cortical bone, using both crack-deflection/twist mechanics and nonlinear-elastic fracture mechanics to determine crack-resistance curves. We find that after only 500 mu m of cracking, the driving force for crack propagation was more than five times higher in the transverse (breaking) direction than in the longitudinal (splitting) direction due to major crack deflections/twists principally at cement sheathes. Indeed, our results show that the true transverse toughness of cortical bone is far higher than previously reported. However, the toughness in the longitudinal orientation, where cracks tend to follow the cement lines, is quite low at these small crack sizes; it is only when cracks become several millimeters in length that bridging mechanisms can develop leading to the (larger-crack) toughnesses generally quoted for bone.
Blunt-crack band propagation in finite-element analysis for concrete structures. [LMFBR
The knowledge of concrete fracture is needed in nuclear reactor safety. The question of safety arises from the potential of concrete to crack under thermal loading. It has been postulated that structural concrete could be exposed to very high temperature, which may result from hot reactor coolant or even core debris coming in direct contact with the concrete. The utilization of the blunt crack approach for simulating concrete cracking in a general-purpose code is explored. The difficulties encountered in establishing the proper direction of crack propagation in an arbitrary discretization are described. Crack propagation is considered within the context of two types of solution techniques: (1) implicit solution of the static crack advance, and (2) explicit time integration using a dynamic relaxation technique to simulate the static crack advance. Also, in both solution techniques an elastic model is used to characterize the concrete.
Pfeiffer, P.A.; Bazant, Z.P.; Marchertas, A.H.
Stress corrosion cracking of candidate waste container materials; Final report
Six alloys have been selected as candidate container materials for the storage of high-level nuclear waste at the proposed Yucca mountain site in Nevada. These materials are Type 304L stainless steel (SS). Type 316L SS, Incoloy 825, phosphorus-deoxidized Cu, Cu-30%Ni, and Cu-7%Al. The present program has been initiated to determine whether any of these materials can survive for 300 years in the site environment without developing through-wall stress corrosion cracks. and to assess the relative resistance of these materials to stress corrosion cracking (SCC)- A series of slow-strain-rate tests (SSRTs) and fracture-mechanics crack-growth-rate (CGR) tests was performed at 93{degree}C and 1 atm of pressure in simulated J-13 well water. This water is representative, prior to the widespread availability of unsaturated-zone water, of the groundwater present at the Yucca Mountain site. Slow-strain-rate tests were conducted on 6.35-mm-diameter cylindrical specimens at strain rates of 10-{sup {minus}7} and 10{sup {minus}8} s{sup {minus}1} under crevice and noncrevice conditions. All tests were interrupted after nominal elongation strain of 1--4%. Scanning electron microscopy revealed some crack initiation in virtually all the materials, as well as weldments made from these materials. A stress- or strain-ratio cracking index ranks these materials, in order of increasing resistance to SCC, as follows: Type 304 SS < Type 316L SS < Incoloy 825 < Cu-30%Ni < Cu and Cu-7%Al. Fracture-mechanics CGR tests were conducted on 25.4-mm-thick compact tension specimens of Types 304L and 316L stainless steel (SS) and Incoloy 825. Crack-growth rates were measured under various load conditions: load ratios M of 0.5--1.0, frequencies of 10{sup {minus}3}-1 Hz, rise nines of 1--1000s, and peak stress intensities of 25--40 MPa{center_dot}m {sup l/2}.
Park, J.Y.; Maiya, P.S.; Soppet, W.K.; Diercks, D.R.; Shack, W.J.; Kassner, T.F. [Argonne National Lab., IL (United States)
Fatigue and Creep Crack Propagation behaviour of Alloy 617 in the Annealed and Aged Conditions
The crack propagation behaviour of Alloy 617 was studied under various conditions. Elevated temperature fatigue and creep-fatigue crack growth experiments were conducted at 650 and 800 degrees C under constant stress intensity (triangle K) conditions and triangular or trapezoidal waveforms at various frequencies on as-received, aged, and carburized material. Environmental conditions included both laboratory air and characteristic VHTR impure helium. As-received Alloy 617 displayed an increase in the crack growth rate (da/dN) as the frequency was decreased in air which indicated a time-dependent contribution component in fatigue crack propagation. Material aged at 650�C did not display any influence on the fatigue crack growth rates nor the increasing trend of crack growth rate with decreasing frequency even though significant microstructural evolution, including y� (Ni3Al) after short times, occurred during aging. In contrast, carburized Alloy 617 showed an increase in crack growth rates at all frequencies tested compared to the material in the standard annealed condition. Crack growth studies under quasi-constant K (i.e. creep) conditions were also completed at 650 degrees C and a stress intensity of K = 40 MPa9 (square root)m. The results indicate that crack growth is primarily intergranular and increased creep crack growth rates exist in the impure helium environment when compared to the results in laboratory air. Furthermore, the propagation rates (da/dt) continually increased for the duration of the creep crack growth either due to material aging or evolution of a crack tip creep zone. Finally, fatigue crack propagation tests at 800 degrees C on annealed Alloy 617 indicated that crack propagation rates were higher in air than impure helium at the largest frequencies and lowest stress intensities. The rates in helium, however, eventually surpass the rates in air as the frequency is reduced and the stress intensity is decreased which was not observed at 650 degrees C.
Julian K. Benz; Richard N. Wright
Energy Spread Reduction of Electron Beams Produced via Laser Wake
Laser wakefield acceleration of electrons holds great promise for producing ultra-compact stages of GeV scale, high quality electron beams for applications such as x-ray free electron lasers and high energy colliders. Ultra-high intensity laser pulses can be self-guided by relativistic plasma waves over tens of vacuum diffraction lengths, to give >1 GeV energy in cm-scale low density plasma using ionization-induced injection to inject charge into the wake at low densities. This thesis describes a series of experiments which investigates the physics of LWFA in the self-guided blowout regime. Beginning with high density gas jet experiments the scaling of the LWFA-produced electron beam energy with plasma electron density is found to be in excellent agreement with both phenomenological theory and with 3-D PIC simulations. It is also determined that self-trapping of background electrons into the wake exhibits a threshold as a function of the electron density, and at the densities required to produce electron beams with energies exceeding 1 GeV a different mechanism is required to trap charge into low density wakes. By introducing small concentrations of high-Z gas to the nominal He background the ionization-induced injection mechanism is enabled. Electron trapping is observed at densities as low as 1.3 x 10{sup 18} cm{sup -3} in a gas cell target, and 1.45 GeV electrons are demonstrated for the first time from LWFA. This is currently the highest electron energy ever produced from LWFA. The ionization-induced trapping mechanism is also shown to generate quasi-continuous electron beam energies, which is undesirable for accelerator applications. By limiting the region over which ionization-induced trapping occurs, the energy spread of the electron beams can be controlled. The development of a novel two-stage gas cell target provides the capability to tailor the gas composition in the longitudinal direction, and confine the trapping process to occur only in a limited, defined region. Using this technique a 460 MeV electron beam was produced with an energy spread of 5%. This technique is directly scalable to multi-GeV electron beam generation with sub-percent energy spreads.
Pollock, B
Integrating Broad-Band High-Fidelity Acoustic Emission Sensors and Array Processing to Study Drying Shrinkage Cracking in Concrete
, cracks can create stress concentrations which can cause further cracking at loads which are well under energy released from the formation of a crack is converted into stress waves which in turn produce Shrinkage Cracking in Concrete Gregory C. McLaskeya,1 , Steven D. Glasera , Christian U. Grosseb
Glaser, Steven D.
"Cracking-the-whip" effect stretches driven polymers
Cracking the whip accelerates the tail of a chain to hit the air loudly and clearly. We proved that the similar acceleration effect causes coil deformation of driven chain-like polymers. We first preformed Monte Carlo simulations of a single driven polymer coil to demonstrate its deformation in company with faster or slower deviations of velocities. We then performed parallel Brownian Dynamics simulations to demonstrate that the coil deformation can be caused by the so-called "cracking-the-whip" effect due to non-synchronous biased Brownian motions of monomers inherited in Monte Carlo simulations. Since such non-synchronous motions represent random perturbations in the environmentally dependent potential energy landscape or mobility, reflecting heterogeneous dynamics of polymers in the liquid phase, our observations bring new insights into the non-linear dynamics of driven chain-like polymers.
Juan Li; Wenbing Hu
Modeling of solar receiver for cracking of liquid petroleum gas
The paper presents the model of an industrial solar receiver/reactor for thermal cracking of liquid petroleum gas (LPG) at the typical temperature range of 800--850 C. The concentrated solar radiation enters the receiver located on the ground and provided with a compound parabolic concentrator (CPC) at the ceiling. This is achieved with a reflecting solar tower. The radiative model uses the classical concept of equivalent gray plane to represent a panel of 40 cracking tubes placed in parallel of a refractory wall of the receiver. The radiative flux distribution on each wall is calculated and the chemistry in each reactor tube is evaluated until convergence is achieved. The design of an industrial size receiver, its behavior, and performance have been evaluated using this model. The computer program based on this model was run for a variety of flow conditions, feed compositions, and pressures.
Segal, A.; Epstein, M. [Weizmann Inst. of Science, Rehovot (Israel). Solar Research Facilities Unit
Longitudinal bunch profile and electron beam energy spread
Magnets and Power Supplies Up: APS Storage Ring Parameters Previous: Magnets and Power Supplies Up: APS Storage Ring Parameters Previous: Storage Ring Operation Modes Longitudinal bunch profile and electron beam energy spread Longitudinal bunch profile depends mainly on the single bunch charge (or single bunch current). Every APS operating mode has different single bunch current and therefore has different bunch length. The plot below shows measured bunch length dependence on the single bunch current between 1 mA and 18 mA and the fit that uses the formula shown below the plot. The bunch length in this plot is shorter than it was quoted before. Earlier numbers were obtained using a Gaussian fit, present numbers are calculated as true standard deviation. \includegraphics[width=0.8\textwidth]{otherFiles/bunchLength.eps} The following formula obtained by fitting the log of the data above can be
Method for making dense crack free thin films
Environmentally assisted cracking of light-water reactor materials
Environmentally assisted cracking (EAC) of lightwater reactor (LWR) materials has affected nuclear reactors from the very introduction of the technology. Corrosion problems have afflicted steam generators from the very introduction of pressurized water reactor (PWR) technology. Shippingport, the first commercial PWR operated in the United States, developed leaking cracks in two Type 304 stainless steel (SS) steam generator tubes as early as 1957, after only 150 h of operation. Stress corrosion cracks were observed in the heat-affected zones of welds in austenitic SS piping and associated components in boiling-water reactors (BRWs) as early as 1965. The degradation of steam generator tubing in PWRs and the stress corrosion cracking (SCC) of austenitic SS piping in BWRs have been the most visible and most expensive examples of EAC in LWRs, and the repair and replacement of steam generators and recirculation piping has cost hundreds of millions of dollars. However, other problems associated with the effects of the environment on reactor structures and components am important concerns in operating plants and for extended reactor lifetimes. Cast duplex austenitic-ferritic SSs are used extensively in the nuclear industry to fabricate pump casings and valve bodies for LWRs and primary coolant piping in many PWRs. Embrittlement of the ferrite phase in cast duplex SS may occur after 10 to 20 years at reactor operating temperatures, which could influence the mechanical response and integrity of pressure boundary components during high strain-rate loading (e.g., seismic events). The problem is of most concern in PWRs where slightly higher temperatures are typical and cast SS piping is widely used.
Chopra, O.K.; Chung, H.M.; Kassner, T.F.; Shack, W.J.
Stress relief cracking in creep resisting low alloy ferritic steels.
The Problem of Stress Relief Cracking in Low Alloy Steels During the welding of a ferritic steel, the HAZ adjacent to the weld transforms to austenite, the grains close to the fusion zone attaining particularly high tempel'ature and undergoing considerable... growth. At the same time, carbides tend to dissolve, dissolution being more complete in the coarse 14 grained region because it attains a higher temperature. The HAZ is cooled rapidly by the cold parent metal and, as a result, re- precipitation...
Tait, Robert Andrew
Gas Turbine Rotor Life: General Electric FA Disc Cracking
This report covers the integrated results of the investigation into the occurrence of cooling slot and other rim cracking found in GE 7FA and 9FA gas turbine first and second stage rotor discs. Sections of the report address dimensional characterization, rim temperature measurement, metallurgical results, analytical methods, evaluation of mitigation approaches, and damage tolerance. Structural stress analysis assessed the effectiveness of the blend-polish-peen slot modification and a redesigned ...
Evaluation of Fundamental Linkage Among Stress Corrosion Cracking (SCC) Phenomena
Many in-core components of stainless steels in light water reactors (LWRs) are susceptible to a degradation process known as irradiation assisted stress corrosion cracking (IASCC). This report describes the results of environmental testing on irradiated Type 304 stainless steel in boiling water reactor (BWR) and pressurized water reactor (PWR) environments to assess their susceptibility to IASCC. The work was sponsored by the Cooperative IASCC Research (CIR I) Program, an international research effort ma...
Computer Simulation of Intergranular Stress Corrosion Cracking via Hydrogen Embrittlement
Computer simulation has been applied to the investigation of intergranular stress corrosion cracking in Ni-based alloys based on a hydrogen embrittlement mechanism. The simulation employs computational modules that address (a) transport and reactions of aqueous species giving rise to hydrogen generation at the liquid-metal interface, (b) solid state transport of hydrogen via intergranular and transgranular diffusion pathways, and (c) fracture due to the embrittlement of metallic bonds by hydrogen. A key focus of the computational model development has been the role of materials microstructure (precipitate particles and grain boundaries) on hydrogen transport and embrittlement. Simulation results reveal that intergranular fracture is enhanced as grain boundaries are weakened and that microstructures with grains elongated perpendicular to the stress axis are more susceptible to cracking. The presence of intergranular precipitates may be expected to either enhance or impede cracking depending on the relative distribution of hydrogen between the grain boundaries and the precipitate-matrix interfaces. Calculations of hydrogen outgassing and in gassing demonstrate a strong effect of charging method on the fracture behavior.
Smith, R.W.
Pilot scale (500 gram) SAES St 909 methane cracking tests were conducted to determine material performance for tritium process applications. Tests that ran up to 1400 hours have been performed at 700 C, 202.7 kPa (1520 torr) with a 30 sccm feed of methane, with various impurities, in a 20 vol% hydrogen, balance helium, stream. A 2.5 vol% methane feed was reduced below 30 ppm for 631 hours. A feed of 1.1 vol% methane plus 1.4 vol% carbon dioxide was reduced below 30 ppm for 513 hours. The amount of carbon dioxide gettered by St 909 can be equated to an equivalent amount of methane gettered to estimate a reduced bed life for methane cracking. The effect of 0.4 vol % and 2.1 vol% nitrogen in the feed reduced the time to exceed 30 ppm methane to 362 and 45 hours, respectively, but the nitrogen equivalence to reduced methane gettering capacity was found to be dependent on the nitrogen feed composition. Decreased hydrogen concentrations increased methane getter rates while a drop of 30 C in one bed zone increased methane emissions by over a factor of 30. The impact of gettered nitrogen can be somewhat minimized if the nitrogen feed to the bed has been stopped and sufficient time given to recover the methane cracking rate.
Klein, J; Henry Sessions, H
Comparing Methods of Estimating Crack Volume in Shrink-Swell Soils
Predicting soil crack formation and closure in high shrink-swell soils is crucial for modeling water movement and solute transport. However, soil cracking, as it occurs in natural conditions, is not well understood. The objectives of this research are to 1) compare shrinking and swelling of two Vertisols with different mineralogy and 2) compare two methods for estimating soil crack volume. The first soil monitored, Ships Clay (Very-fine, mixed, thermic Chromic Hapluderts) has mixed mineralogy and is located in Snook, TX. The second soil monitored is a Burleson Clay (Fine, smectitic, thermic Udic Haplusterts), which has smectitic mineralogy and is located 1 mile southwest of the Ships site. During two drying events, vertical subsidence and cracking were measured on both soils. Vertical subsidence was measured at three locations in each soil with rods fixed at four depths. Rod movement was converted to soil crack volume by assuming equi-dimensional shrinkage. A second method for estimating crack volume used direct measurements of cracks in the field. This second method was time consuming and the accuracy is unknown. A neutron moisture meter access tube was installed to measure soil moisture at each subsidence location. A total of 20 levling and moisture measurements were completed and 10 hand measurements of cracking were made. At the completion of the study, full characterization of each measurement location was performed, including COLE measurements. These COLE measurements were used as a third method of estimating crack volume in relation to soil moisture. Total crack volume will be compared at both sites to show the differences in the drying and cracking patterns. Crack volume as a function of moisture will be used to show how soil cracking and moisture relate. The two methods of estimating crack volume will be compared to see where possible cracking was measured with subsidence but not seen visually. The results showed the leveling-predicted crack volume was ten times that of the hand measured crack volume but followed the same temporal trend. The leveling-predicted crack volume is the most accurate of the three methods. COLE was also shown to be a good predictor a soils shrink-swell potential.
Rivera, Leonardo D.
Fatigue Crack Propagation from Notched Specimens of 304 SS in elevated Temperature Aqueous Environment
Fatigue crack propagation (FCP) rates for 304 stainless steel (304SS) were determined in 24 degree C and 288 degree C air and 288 degree C water using double-edged notch (DEN) specimens of 304 stainless steel (304 SS). Test performed at matched loading conditions in air and water at 288 degree C with 20-6- cc h[sub]2/kg h[sub]2O provided a direct comparison of the relative crack growth rates in air and water over a wide range of crack growth rates. The DEN crack extension ranged from short cracks (0.03-0.25 mm) to long cracks up to 4.06 mm, which are consistent with conventional deep crack tests. Crack growth rates of 304 SS in water were about 12 times the air rate. This 12X environmental enhancement persisted to crack extensions up to 4.06 mm, far outside the range associated with short crack effects. The large environmental degradation for 304 SS crack growth is consistent with the strong reduction of fatigue life in high hydrogen water. Further, very similar environmental effects w ere reported in fatigue crack growth tests in hydrogen water chemistry (HWC). Most literature data in high hydrogen water show only a mild environmental effect for 304 SS, of order 2.5 times air or less, but the tests were predominantly performed at high cyclic stress intensity or equivalently, high air rates. The environmental effect in low oxygen environments at low stress intensity depends strongly on both the stress ratio, R, and the load rise time, T[sub]r, as recently reported for austenitic stainless steel in BWR water. Fractography was performed for both tests in air and water. At 288 degree C in water, the fracture surfaces were crisply faceted with a crystallographic appearance, and showed striations under high magnification. The cleavage-like facets on the fracture surfaces suggest that hydrogen embrittlement is the primary cause of accelerated cracking.
Wire, G. L.; Mills, W. J.
Measurement of gas temperature field in a flame spreading over solid fuel.
??An experimental measurement is developed to measure the gas temperature field in a flame spreading downward over thermally thin filter paper. A flame stabilizer apparatus� (more)
Alghamdi, Abdulaziz Othman
Uranium fuel, nuclear reactors, generation, spent fuel. Total Energy. ... and quark spreads (electricity price minus the cost of enriched uranium fuel) ...
On the micromechanisms of fatigue-crack propagation in aluminum- lithium alloys: Sheet vs. plate material
Micromechanisms influencing the propagation of long (>10 mm) fatigue cracks in aluminum-lithium alloys are examined by specifically comparing crack-growth kinetics in a peak-aged Al-Li-Cu-Zr alloy 2090, processed as 1.6-mm thin (T83) sheet and 12.7-mm thick (T81) plate. It is found that in general crack-growth rates are significantly faster in the sheet material at equivalent stress-intensity levels, due to differences in the role of crack-tip shielding, resulting from crack deflection and consequent crack closure from wedging of fracture-surface asperities. Microstructurally, such differences are related to variations in the degree of recrystallization, grain structure and deformation texture in the two wrought-product forms. 14 refs., 4 figs.
Rao Venkateswara, K.T.; Ritchie, R.O. (Lawrence Berkeley Lab., CA (United States) California Univ., Berkeley, CA (United States). Dept. of Materials Science and Mineral Engineering); Bucci, R.J. (Aluminum Co. of America, Alcoa Center, PA (United States). Alcoa Labs.)
Cessation of environmentally-assisted cracking in a low-alloy steel: Experimental results
The presence of dissolved metallurgical sulfides in pressure vessel and piping steels has been linked to Environmentally-Assisted Cracking (EAC), a phenomenon observed in laboratory tests that results in fatigue crack growth rates as high as 100 times that in air. Previous experimental and analytical work based on diffusion as the mass transport process has shown that surface cracks that are initially clean of sulfides will not initiate EAC in most applications. This is because the average crack tip velocity would not be sufficiently high to expose enough metallurgical sulfides per unit time and produce the sulfide concentration required for EAC. However, there is a potential concern for the case of a relatively large embedded crack breaking through to the wetted surface. Such a crack would not be initially clean of sulfides, and EAC could initiate. This paper presents the results of a series of experiments conducted on two heats of an EAC susceptible, high-sulfur, low-alloy steel in 243{degrees}C low-oxygen water to further study the phenomenon of EAC persistence at low crack tip velocities. A load cycle profile that incorporated a significant load dwell period at minimum load was used. In one experiment, the fatigue cycling history was such that relatively high crack tip velocities at the start of the experiment produced a persistent case of EAC even when crack tip velocities were later reduced to levels below the EAC initiation velocity. The other series of experiments used initial crack tip velocities that were much lower and probably more realistic. Air precracking of the compact tension specimens produced an initial inventory of undissolved sulfides on the crack flanks that directly simulates the array of sulfides expected from the breakthrough of an embedded crack. In all cases, results showed EAC ceased after several hundred hours of cycling.
Li, Y.Y.
Significance of crack opening monitoring for determining the growth behavior of hydrofractures
A method for determining the size of a crack induced by hydraulic fracturing is presented. The procedure is based on the measurement of the crack opening displacement and the fracture mechanics approach. The proposed method has been tested by conducting laboratory small-scale hydraulic fracturing tests on a granite. It is shown from the preliminary tests that the method provides a reasonable prediction of experimentally observed crack sizes.
Hashida, Toshiyuki; Sato, Kazushi; Takahashi, Hideaki
Documents of the Davis-Besse incident reveal a strong possibility that there are large numbers of undetected cracks in the world�s pressurized water reactors, particularly in the US. This suspicion has been confirmed by the discovery of an additional crack at Davis-Besse itself. (568.5402) NIRS/WISE Amsterdam � The cracks are nothing new: they were first discovered in Bugey-3,
unknown authors
RQL: Global placement via relaxed quadratic spreading and linearization
This paper describes a simple and effective quadratic placement algorithm called RQL. We show that a good quadratic placement, followed by local wirelength-driven spreading can produce excellent results on large-scale industrial ASIC designs. As opposed to the current top performing academic placers [4,7,11], RQL does not embed a linearization technique within the solver. Instead, it only requires a simpler, pure quadratic objective function in the spirit of [8,10,23]. Experimental results show that RQL outperforms all available academic placers on the ISPD-2005 placement contest benchmarks. In particular, RQL obtains an average wirelength improvement of 2.8%, 3.2%, 5.4%, 8.5%, and 14.6% versus mPL6 [5], NTUPlace3 [7], Kraftwerk [20], APlace2.0 [11], and Capo10.2 [18], respectively. In addition, RQL is three, seven, and ten times faster than mpL6, Capo10.2, and APlace2.0, respectively. On the ISPD-2006 placement contest benchmarks, on average, RQL obtains the best scaled wirelength among all available academic placers.
Natarajan Viswanathan; Gi-joon Nam; Charles J. Alpert; Paul Villarrubia; Haoxing Ren; Chris Chu
Cyclic Deformation and Fatigue Cracking Mechanisms of F.C.C. ...
Fatigue Crack Tip Mechanics Following a Tensile Overload � Fatigue Weak-Link Density and Strength Distribution in High Strength Al Wrought and Cast Alloys.
Manufacturing of Crack-Free Hastelloy-X Components by Selective ...
Lubricants in Deposition and Machining of Wire and Arc Additive Manufactured Structures � Manufacturing of Crack-Free Hastelloy-X Components by Selective�...
Innovative Approach to Establish Root Causes for Cracking in Aggressive Reactor Environments
The research focuses on the high-resolution characterization of degradation microstructures and microchemistries in specimens tested under controlled conditions for the environment and for the material where in-service complexities can be minimized. Thermodynamic and kinetic modeling of crack-tip processes is employed to analyze corrosion-induced structures and gain insights into degradation mechanisms. Novel mechanistic ''fingerprinting'' of crack-tip structures is used to isolate causes of environmental cracking in tandem with quantitative measurements of crack growth. Sample preparation methods and advanced analytical techniques are used to characterize corrosion/oxidation reactions and crack-tip structures at near atomic dimensions in order to gain insight into fundamental environmental cracking mechanisms. Reactions at buried interfaces, not accessible by conventional approaches, are being systematically interrogated. Crack-growth experiments in high-temperature water environments are evaluating and isolating the effects of material condition (matrix strength, grain boundary composition and precipitation) on stress corrosion cracking (SCC). The fundamental understanding of crack advance mechanisms will establish the basis to design new corrosion-resistant alloys for current light-water reactors and advanced reactor systems.
Bruemmer, Stephen M.; Thomas, Larry E.; Vetrano, John S.; Simonen, Edward P.
A model of crack based on dislocations in smectic A liquid crystals
A plastic crack model for smectic A liquid crystals under longitudinal shear is suggested. The solution of screw dislocation in smectic A is the key in which the correct result is just obtained by overcoming a longstanding puzzle [19]. We further use the dislocation pile-up principle and the singular integral equation method, construct the solution of the crack in the phase. From the solution we can determine the size of the plastic zone at the crack tip and the crack tip opening (tearing) displacement, which are parameters being relevant to the local stability/instability of materials. The results may be useful in developing soft-matter mechanics.
Tian You Fan
Elevated-Temperature Creep-Fatigue Crack-Growth Behavior of ...
the nickel-base HAYNES R-41, HAYNES 230 and HASTELLOY. X superalloys at temperatures ... The crack-growth tests for R-41 alloy were conducted using a.
Stress Corrosion Cracking Behavior of Cast Stainless Steels
Casting of austenitic stainless steels offers the possibility of directly producing large and/or relatively complex structures, such as the first wall shield modules or the diverter cassette for the ITER fusion reactor. Casting offers major cost savings when compared to fabrication via welding of quarter modules machined from large forgings. However, the strength properties of such cast components are typically considered inferior to those of conventionally forged and annealed components. To improve and validate cast stainless steel as a substitute for wrought stainless steel, a development and testing program was initiated, utilizing nitrogen and manganese additions to promote improved performance. This paper focuses on the response of the first set of developmental alloys to neutron-irradiation and susceptibility to stress corrosion cracking. These cast materials may also have applications for different components in light water reactors. Results showed that all steels exhibited irradiation-induced hardening and a corresponding drop in ductility, as expected, although there is still considerable ductility in the irradiated samples. The cast steels all exhibited reduced hardening in comparison to a wrought reference steels, which may be related to a larger grain size. Higher nitrogen contents did not negatively influence irradiation performance. Regarding stress corrosion cracking susceptibility, the large difference in grain size limits the comparison between wrought and cast materials, and inclusions in a reference and archive cast alloy tests complicate analysis of these samples. Results suggest that the irradiated archive heat was more susceptible to cracking than the modified alloys, which may be related to the more complex microstructure. Further, the results suggest that the modified cast steel is at least as SCC resistant as wrought 316LN. The beneficial effect of nitrogen on the mechanical properties of the alloys remains after irradiation and is not detrimental to SCC resistance.
Teysseyre, Sebastien [University of Michigan; Busby, Jeremy T [ORNL; Was, Gary [University of Michigan
Temperature and environmentally assisted cracking in low alloy steel
Environmental assisted cracking (EAC) can be defined as the propagation of fatigue cracks in water at rates from 3 to over 40 times the growth rates in air. For low alloy steels with sulfur contents > 0.0125% by weight, EAC is normal behavior in the 240 to 290C range. However, literature yields mixed results for low alloy steels with compositions just below this sulfur level; some reports indicate EAC while others do not. Also, several authors have reported an increased tendency toward EAC when the water temperatures were lowered. In the present work, five ASTM A 508 Class 2 forgings with ladle and check analyses that ranged from 0.010 to 0.019 wt% S were tested in high purity deaerated water in the temperature range of 93 to 260C. At 260C these forgings did not exhibit EAC, reinforcing earlier results for two similar forgings. This broad sampling indicates strong resistance to EAC for this class of forging at 260C. On the other hand, EAC occurred consistently in the three of these forgings that were tested below 204C, provided the test conditions (loading frequency, {Delta}K, and R) were high enough to produce a high baseline fatigue crack growth rate (FCGR), where the baseline FCGR is that expected in air. At 149C, EAC occurred at test conditions that combined to yield a baseline FCGR greater than {approx}2E-6 mm/s. At 204, 121, and 93C, this critical crack growth rate appeared to shift to lower baseline values. The EAC that occurred at lower temperatures was a factor of 3 to 12 times higher than baseline air rates, which was not as strong as the effect for higher sulfur steels at 240 to 290C. Also, no plateau in the growth rates occurred as it does with the higher sulfur steels. In another approach, EAC was induced at 93 and at 260C by raising the dissolved oxygen content of the water from 15 ppb.
Auten, T.A.; Monter, J.V.
Physics-Based Stress Corrosion Cracking Component Reliability
Physics-Based Stress Corrosion Physics-Based Stress Corrosion Cracking Component Reliability Model cast in an R7-Compatible Cumulative Damage Framework Draft Report Supporting Technology Inputs to the Risk- Informed Safety Margin Characterization Pathway of the DOE Light Water Reactor Sustainability Program Stephen D. Unwin Kenneth I. Johnson Robert F. Layton Peter P. Lowry Scott E. Sanborn Mychailo B. Toloczko PNNL-20596 July 2011 Physics-Based SCC Reliability Model in a Cumulative Damage Framework 2 Physics-Based SCC Reliability Model in a Cumulative Damage Framework 3 Table of Contents Executive Summary............................................................................... 4 1. Introduction .......................................................................... 5
Methods for special applications: Cell-DEVS quantization techniques in a fire spreading application
We present the use of the CD++ tool to model and simulate forest fire-spread. A semi-physical fire spread model is implemented using the Cell-DEVS formalism. The use of Cell-DEVS enables proving the correctness of the simulation engines and permits to ...
A numerical method for solving convection-reaction-diffusion multivalued equations in fire spread modelling
A numerical method is developed for fire spread simulation modelling. The two-dimensional surface model presented takes into account moisture content, radiation, wind and slope effects, which are by far the most important mechanisms in fire spread. We ... Keywords: 02.60.Cb, 02.60.Lj, 02.70.Dh, Fire, Moisture, Pyrolysis, Radiation, Slope, Wind
L. Ferragut; M. I. Asensio; S. Monedero
Analysis of the Spread�Skill Relations Using the ECMWF Ensemble Prediction System over Europe
The Ensemble Prediction System (EPS) of the European Centre for Medium-Range Weather Forecasts (ECMWF) was used to analyze various aspects of the ensemble-spread forecast-skill relation. It was shown that synoptic-scale upper-air spread measures ...
Simon C. Scherrer; Christof Appenzeller; Pierre Eckert; Daniel Cattani
Intensity and mosaic spread analysis from PISEMA tensors in solid-state NMR
Intensity and mosaic spread analysis from PISEMA tensors in solid-state NMR J.R. Quine a,b,*, S 2005 Available online 18 January 2006 Abstract The solid-state NMR experiment PISEMA, is a technique: PISEMA tensors; Solid-state NMR; Powder pattern intensity; Mosaic spread; Lineshapes 1. Introduction
Aluffi, Paolo
A low-power digital matched filter for spread-spectrum systems
A Digital Matched Filter (DMF) is an essential device for Direct-Sequence Spread-Spectrum (DS-SS) communication systems. Reducing the power consumption of a DMF is especially critical for battery-powered terminals. The reception registers and the correlation-calculating ... Keywords: CDMA, VLSI, low power, matched filter, spread-spectrum
Shoji Goto; Takashi Yamada; Norihisa Takayama; Yoshifumi Matsushita; Yasoo Harada; Hiroto Yasuura
Corium Spreading Over Concrete: The Vulcano VE-U7 and VE-U8 Tests
Two experiments have been performed in the VULCANO facility in which prototypic corium has been spread over concrete. In the VE-U7 test, a mixture representative of what can be expected at the opening of EPR reactor-pit gate has been spread on siliceous concrete and on a reference channel in inert refractory ceramic. The spreading progression was not much affected by the presence of concrete and sparging gases. In the VE-U8 test, a UO{sub 2}-ZrO{sub 2} mixture, prototypic of in-vessel corium, has been spread over a lime-siliceous concrete. Although residual power was not simulated in this experiment, up to 2 cm of concrete have been eroded during the test. Results in terms of spreading behaviour, effects of gases, concrete erosion and thermal attack are presented and discussed. (authors)
Journeau, Christophe; Boccaccio, Eric; Fouquart, Pascal; Jegou, Claude; Piluso, Pascal [CEA Cadarache, F-13108 St Paul lez Durance cedex (France)
Residual stresses and stress corrosion cracking in pipe fittings
Residual stresses can play a key role in the SCC performance of susceptible materials in PWR primary water applications. Residual stresses are stresses stored within the metal that develop during deformation and persist in the absence of external forces or temperature gradients. Sources of residual stresses in pipe fittings include fabrication processes, installation and welding. There are a number of methods to characterize the magnitude and orientation of residual stresses. These include numerical analysis, chemical cracking tests, and measurement (e.g., X-ray diffraction, neutron diffraction, strain gage/hole drilling, strain gage/trepanning, strain gage/section and layer removal, and acoustics). This paper presents 400 C steam SCC test results demonstrating that residual stresses in as-fabricated Alloy 600 pipe fittings are sufficient to induce SCC. Residual stresses present in as-fabricated pipe fittings are characterized by chemical cracking tests (stainless steel fittings tested in boiling magnesium chloride solution) and by the sectioning and layer removal (SLR) technique.
Parrington, R.J.; Scott, J.J.; Torres, F.
Prediction of Environmental Crack Growth in Nuclear Power Plant Components: Volumes 1-3
In-service assessment of crack growth rates plays a crucial role in decisions involving component integrity and life. The research presented in this three-volume report examines many important aspects of the crack tip damage processes in aqueous environments, providing an improved scientific basis for life prediction technology development.
Influence of Radiolysis and Hydrogen Embrittlement on the In-Service Cracking of PWR Internal Structures
Irradiation-assisted stress corrosion cracking (IASCC) of austenitic stainless steel components exposed to a high neutron flux in light water reactors is becoming an increasing concern for nuclear power plant owners. This study investigates the interaction between hydrogen in the metal and the water environment that may exacerbate the cracking process in PWRs.
On saturation-strip model of a permeable crack in a piezoelectric ceramic
, h0, in the analysis of electrical and mechanical fields in the vicinity of a permeable crack tip under both mechanical as well electrical loads. Both local and global energy release rates. This permeable saturation crack model reveals that there exists a possible leaky mode for electrical field, which
Li, Shaofan
Thermal stress cracking and the enhancement of heat extraction from fractured geothermal reservoirs
Given sufficient time, the extraction of heat from geothermal reservoirs formed by the hydraulic fracturing of competent rock will eventually result in the formation of thermal stress cracks in the reservoir. These cracks penetrate the rock in a manner such that the penetration-to-spacing ratio is approximately one. The penetration depends upon the extent of cooling and the square root of time. Initially then, the cracks are closely spaced and penetrate but little, so that a crazing pattern is apparent; but with increasing time some of these cracks, now more widely spaced, grow deeper. Eventually these larger cracks attain a critical aperture such that significant rates of water flow can be established within them and thus the newly created heat transfer area becomes useful for heat extraction. At the same time that cracks are forming within the main reservoir, thermal cracking also occurs in the wellbores that communicate with the reservoir. These cracks eventually convey water to and from the reservoir, thus leading to a decrease in the flow impedances that are often concentrated in the wellbore regions.
Fatigue Crack Growth Characteristics of Thin Sheet Titanium Alloy Ti 6-2-2-2-2
Fatigue crack growth rates of Ti 6-2-2-2-2 as a function of stress ratio, temperature (24 or 177 degrees C), tensile orientation and environment (laboratory air or ultrahigh vacuum) are presented. Fatigue crack growth rates of Ti 6-2-2-2-2 are also compared ...
Smith Stephen W.; Piascik Robert S.
Behavior of Stress Corrosion Cracking for Type 316L Stainless Steel ...
Crack Growth Rates of Irradiated Commercial Stainless Steels in BWR and PWR ... Detailed Root Cause Analysis of SG Tube ODSCC Indications within the Tube Sheets of NPP Biblis Unit A .... Radiation Damage in Fe-C-Met Model Alloys ... Stress Corrosion Cracking Behavior near the Fusion Boundary of Dissimilar Weld
Apparatus and method for prevention of cracking in welded brittle alloys
An apparatus and method for reducing cracking in a heated material as the material cools. The apparatus includes a variable frequency electric signal generator that is coupled to a transducer. The transducer produces a variable frequency acoustic signal in response to the variable frequency electric signal, which is applied to the heated material to reduce cracking as the material cools.
Kronberg, James W. (Aiken, SC); Younkins, Robert M. (New Ellenton, SC)
Delamination of a sensitized commercial AlMg alloy during fatigue crack growth
as sensitization to corrosion and stress corrosion cracking [1,3,4,8], with exposure to tem- peratures between 50,912]. The presence and growth of b-phase have been shown to severely degrade the corrosion resistance and stressDelamination of a sensitized commercial AlMg alloy during fatigue crack growth J.K. Brosi and J
Rollins, Andrew M.
Average crack front velocity during subcritical fracture propagation in a heterogeneous medium
the free energy, and thus the energy barrier, via numerous competing mech- anisms like stress corrosion speed of crack growth with increasing G; a weak stress- sensitive regime II follows where transportAverage crack front velocity during subcritical fracture propagation in a heterogeneous medium
Ampuero, Jean Paul
Spectroscopic studies on the formation of coke on individual Fluid Catalytic Cracking particles: the effect of poisoning metal compounds.
??The formation of coke on individual Fluid Catalytic Cracking (FCC) catalyst particles was studied using UV/Vis microspectroscopy and confocal fluorescence microscopy, with n-hexane cracking as� (more)
Goetze, J.G.
Vickers microindentation toughness of a sintered SiC in the median-crack regime
The Vickers microindentation method for the determination of the fracture toughness of ceramics was investigated in the median crack regime for a sintered alpha SiC. The results are compared with fracture toughness measurements by conventional fracture mechanics technique and also with the reported indentation toughness for the low-load Palmqvist crack regime. Indentation toughnesses in the median crack regime vary widely depending on the choice of the specific equation which is applied. The indentation toughnesses are also load (crack length) dependent. A decreasing R-curve trend results, in contradiction to the flat R-curve that has been observed with conventional fracture mechanics techniques. It is concluded that the Vickers microindentation method is not a reliable technique for the determination of the fracture toughness of ceramics in the median crack regime.
Ghosh, Asish; Kobayashi, A.S. (Washington Univ., Seattle, WA (United States). Coll. of Engineering); Li, Zhuang (Argonne National Lab., IL (United States)); Henager, C.H. Jr. (Pacific Northwest Lab., Richland, WA (United States)); Bradt, R.C. (Nevada Univ., Reno, NV (United States). Mackay School of Mines)
BWRVIP-99-A: BWR Vessel and Internals Project, Crack Growth Rates in Irradiated Stainless Steels in BWR Internal Components
The BWR Vessel and Internals Project (BWRVIP) has developed methodologies to evaluate crack growth in internal components of stainless steel and nickel-base alloys in the BWR vessel. One BWRVIP report�BWRVIP-14�developed an approach to evaluate crack growth by intergranular stress corrosion cracking in austenitic stainless steel core shrouds exposed to a limited amount of neutron irradiation. Subsequently another report�BWRVIP-99�was prepared to provide a crack growth methodology applicable to irradiated...
Assessment of Cracks in Stress Concentration Regions with Localized Plastic Zones
Marty brittle fracture evaluation procedures include plasticity corrections to elastically computed stress intensity factors. These corrections, which are based on the existence of a plastic zone in the vicinity of the crack tip, can overestimate the plasticity effect for a crack embedded in a stress concentration region in which the elastically computed stress exceeds the yield strength of the material in a localized zone. The interactions between the crack, which acts to relieve the high stresses driving the crack, plasticity effects in the stress concentration region, and the nature and source of the loading are examined by formulating explicit flaw finite element models for a crack emanating from the root of a notch located in a panel subject to an applied tensile stress. The results of these calculations provide conditions under which a crack-tip plasticity correction based on the Irwin plastic zone size overestimates the plasticity effect. A failure assessment diagram (FAD) curve is used to characterize the effect of plasticity on the crack driving force and to define a less restrictive plasticity correction for cracks at notch roots when load-controlled boundary conditions are imposed. The explicit flaw finite element results also demonstrate that stress intensity factors associated with load-controlled boundary conditions, such as those inherent in the ASME Boiler and Pressure Vessel Code as well as in most handbooks of stress intensity factors, can be much higher than those associated with displacement-controlled conditions, such as those that produce residual or thermal stresses. Under certain conditions, the inclusion of plasticity effects for cracks loaded by displacement-controlled boundary conditions reduces the crack driving force thus justifying the elimination of a plasticity correction for such loadings. The results of this study form the basis for removing unnecessary conservatism from flaw evaluation procedures that utilize plasticity corrections.
Friedman, E.
Material properties effects on the detonation spreading and propagation of diaminoazoxyfurazan (DAAF)
Recent dynamic testing of Diaminoazoxyfurazan (DAAF) has focused on understanding the material properties affecting the detonation propagation, spreading, behavior and symmetry. Small scale gap testing and wedge testing focus on the sensitivity to shock with the gap test including the effects of particle size and density. Floret testing investigates the detonation spreading as it is affected by particle size, density, and binder content. The polyrho testing illustrates the effects of density and binder content on the detonation velocity. Finally the detonation spreading effect can be most dramatically seen in the Mushroom and Onionskin tests where the variations due to density gradients, pressing methods and geometry can be seen on the wave breakout behavior.
Francois, Elizabeth Green [Los Alamos National Laboratory; Morris, John S [Los Alamos National Laboratory; Novak, Alan M [Los Alamos National Laboratory; Kennedy, James E [HERE LLC
Extent of surface regions near corner points of notched cracked bodies subjected to mode-I loading
In the present paper, the extent of surface regions in cracked bodies subjected to mode-I loading was examined, which is important for a proper definition of finite element meshes. Different specimen geometries with and without lateral notches, representative ... Keywords: Crack shape evolution, Extent of surface region, Fatigue crack growth, Finite element method, Stress triaxiality
R. Branco; F. V. Antunes; L. C. H. Ricardo; J. D. Costa
Applying neural networks, genetic algorithms and fuzzy logic for the identification of cracks in shafts by using coupled response measurements
This paper considers the dynamic behavior of a shaft with two transverse cracks characterized by three measures: position, depth and relative angle. Both cracks are considered to lie along arbitrary angular positions with respect to the longitudinal ... Keywords: Coupling, Crack identification, Genetic algorithms, Neural networks, Shaft
K. M. Saridakis; A. C. Chasalevris; C. A. Papadopoulos; A. J. Dentsoras
Vortex flow in the technology of radiation wave cracking (RWC)
This article examines the theory of vortex flows in relation to the processes occurring in the radiation-wave cracking of crude oil, when the crude oil is sprayed into the gas stream in the form of a mist and then is fed into the reactor, where it is treated by the accelerated electrons and the UHF radiation. The output of this process are the products with the specified parameters (high-octane petroleum products). This process operates at the ambient pressure and temperature, which makes the process safer for industrial purposes. Besides the process itself, the authors described the equipment used in this process, as well as the parameters of the optimal process.
L. A. Tsoy; V. N. Kolushov; A. G. Komarov; A. N. Tsoy
Tsoy, L A; Komarov, A G; Tsoy, A N
EMAT based inspection of natural gas pipelines for SSC cracks
EMAT-Based Inspection of Natural Gas EMAT-Based Inspection of Natural Gas Pipelines for Stress Corrosion Cracks FY2004 Report Venugopal K. Varma, Raymond W. Tucker, Jr., and Austin P. Albright Oak Ridge National Laboratory Oak Ridge, Tennessee 37831 1 This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name,
Defects and Flaws control the structural and functional property of ceramics. In determining the reliability and lifetime of ceramics structures it is very important to quantify the crack growth behavior of the ceramics. In addition, because of the high variability of the strength and the relatively low toughness of ceramics, a statistical design approach is necessary. The statistical nature of the strength of ceramics is currently well recognized, and is usually accounted for by utilizing Weibull or similar statistical distributions. Design tools such as CARES using a combination of strength measurements, stress analysis, and statistics are available and reasonably well developed. These design codes also incorporate material data such as elastic constants as well as flaw distributions and time-dependent properties. The fast fracture reliability for ceramics is often different from their time-dependent reliability. Further confounding the design complexity, the time-dependent reliability varies with the environment/temperature/stress combination. Therefore, it becomes important to be able to accurately determine the behavior of ceramics under simulated application conditions to provide a better prediction of the lifetime and reliability for a given component. In the present study, Yttria stabilized Zirconia (YSZ) of 9.6 mol% Yttria composition was procured in the form of tubes of length 100 mm. The composition is of interest as tubular electrolytes for Solid Oxide Fuel Cells. Rings cut from the tubes were characterized for microstructure, phase stability, mechanical strength (Weibull modulus) and fracture mechanisms. The strength at operating condition of SOFCs (1000 C) decreased to 95 MPa as compared to room temperature strength of 230 MPa. However, the Weibull modulus remains relatively unchanged. Slow crack growth (SCG) parameter, n = 17 evaluated at room temperature in air was representative of well studied brittle materials. Based on the results, further work was planned to evaluate the strength degradation, modulus and failure in more representative environment of the SOFCs.
S. Bandopadhyay; N. Nagabhushana
Real &me numerical forecast of global epidemic spreading using large-scale computa&onal models
Real &me numerical forecast of global epidemic spreading using large conditions). Forecast = best prediction given the present knowledge on the system. Projection = attempt functionalities) #12;Real time forecast for the H1N1pdm (2009) Key parameters
Cattuto, Ciro
Undulator-Based Laser Wakefield Accelerator Electron Beam Energy Spread and Emittance Diagnostic
The design and current status of experiments to couple the Tapered Hybrid Undulator (THUNDER) to the Lawrence Berkeley National Laboratory (LBNL) laser plasma accelerator (LPA) to measure electron beam energy spread and emittance are presented.
Bakeman, M.S.; Van Tilborg, J.; Nakamura, K.; Gonsalves, A.; Osterhoff, J.; Sokollik, T.; Lin, C.; Robinson, K.E.; Schroeder, C.B.; Toth, Cs.; Weingartner, R.; Gruner, F.; Esarey, E.; Leemans, W.P.
The spread of violent civil conflict : rare state-driven, and preventable
This dissertation advances and tests an explanation for the spread of violent civil conflict from one state to another. The fear of such "substate conflict contagion" is frequently invoked by American policymakers as a ...
Black, Nathan Wolcott
The tectonics and three-dimensional structure of spreading centers--microearthquake studies and tomographic inversions
Two-thirds of the Earth's surface has been formed along a global system of spreading centers that are presently manifested in several different structural forms, including the classic rift valley of the Mid-Atlantic Ridge, ...
Toomey, Douglas R
A Metric of Influential Spreading during Contagion Dynamics through the Air Transportation Network
The spread of infectious diseases at the global scale is mediated by long-range human travel. Our ability to predict the impact of an outbreak on human health requires understanding the spatiotemporal signature of early-time ...
Nicolaides, Christos
The Downwind Spread of an Initially Vertical Column of Particles in a Sheared Environment
The effects of particle fallspeeds on the downwind spread of initially vertical columns or curtains are examined in environments with wind shear. Sets of equations describing the column width as a function of time and distance below column top ...
Ronald E. Stewart; John D. Marwitz
Laboratory investigation of the impact of lateral spreading on buoyancy flux in a river plume
We investigate the relationship between lateral spreading and mixing in stratified gravity currents by comparing laterally confined and unconfined currents in a series of laboratory experiments. The vertical turbulent buoyancy flux is determined ...
Yeping Yuan; Alexander R. Horner-Devine
Influence of Wave Propagation on the Doppler Spreading of Atmospheric Gravity Waves
The �Doppler spread� theory of atmospheric gravity waves has developed rapidly in recent years, from an initial theory of wave spectra into a general parameterization of gravity wave effects for use in global models of the middle atmosphere. Yet ...
Stephen D. Eckermann
Consistent Scale Interaction of Gravity Waves in the Doppler Spread Parameterization
The standard Doppler spread parameterization of gravity waves, which was proposed by C.-O. Hines and has been applied in a number of middle atmosphere general circulation models, is extended by the inclusion of all effects associated with ...
Erich Becker; Charles McLandress
Energy Tax Credits: Secretary Chu is Spreading the Word, and You Should,
Energy Tax Credits: Secretary Chu is Spreading the Word, and You Energy Tax Credits: Secretary Chu is Spreading the Word, and You Should, Too! Energy Tax Credits: Secretary Chu is Spreading the Word, and You Should, Too! March 29, 2010 - 7:30am Addthis Allison Casey Senior Communicator, NREL As we've mentioned many times on the Energy Savers blog, you can receive up to $1,500 in tax credits for home energy efficiency improvements like adding insulation, installing energy efficient windows, or replacing water heaters. If you're a regular reader, you know that we write about tax credits a lot. Our reasons are simple: we don't want you to forget that these credits are available, and we hope you'll help spread the word by sharing this info with your friends and family. (There are even some handy links at the bottom for you to send this article to your favorite social media
Second Price Component: Spread Impacted by Distillate Supply/Demand Balance
8 8 Notes: While crude oil prices will be a major factor impacting distillate prices this winter, another important factor is the U.S. distillate supply/demand balance, as measured by distillate stocks. The distillate supply/demand balance influences the spread between spot distillate and spot crude oil prices. For example, when stocks are higher than normal, the spread will be lower than usual. This spread is the price incentive that encourages or discourages changes in supply. While high stocks in the distillate market are good news for consumers, an excess is bad news for refiners. Distillate spreads during the winter of 1998-99 and throughout most of 1999 were well below average. Distillate stocks were very high during this period, partially as a result of warm weather keeping demand down.
Secretary Chu is Spreading the Word, and You Secretary Chu is Spreading the Word, and You Should, Too! Energy Tax Credits: Secretary Chu is Spreading the Word, and You Should, Too! March 29, 2010 - 7:30am Addthis Allison Casey Senior Communicator, NREL As we've mentioned many times on the Energy Savers blog, you can receive up to $1,500 in tax credits for home energy efficiency improvements like adding insulation, installing energy efficient windows, or replacing water heaters. If you're a regular reader, you know that we write about tax credits a lot. Our reasons are simple: we don't want you to forget that these credits are available, and we hope you'll help spread the word by sharing this info with your friends and family. (There are even some handy links at the bottom for you to send this article to your favorite social media
SmartPower Spreading Energy Efficiency to Echo-boomers | Department of
SmartPower Spreading Energy Efficiency to Echo-boomers SmartPower Spreading Energy Efficiency to Echo-boomers SmartPower Spreading Energy Efficiency to Echo-boomers April 9, 2010 - 4:36pm Addthis Paul Lester Communications Specialist, Office of Energy Efficiency and Renewable Energy What are the key facts? Research shows that once young people start unplugging unused electronic devices, they are likely to take more action to reduce their energy use. Saving energy is cool. That's the message SmartPower is spreading online to 80 million echo-boomers, the generation born between 1982 and 1995. "They are the generation that best appreciates the need for mitigation of climate change," says Jonathan Edwards, vice president of SmartPower, a non-profit that has developed creative Web marketing campaigns aimed at
Crack Formation in the Presence of an Electric Field in Droplets of Laponite Gel
When a colloidal gel dries through evaporation, cracks are usually formed, which often reveal underlying processes at work during desiccation. Desiccating colloid droplets of few hundred $\\mu l$ size show interesting effects of pattern formation and cracking which makes this an active subject of current research. Since aqueous gels of clay are known to be strongly affected by an electric field, one may expect crack patterns to exhibit a field effect. In the present study we allow droplets of laponite gel to dry under a radial electric field. This gives rise to highly reproducible patterns of cracks, which depend on the strength, direction and time of exposure to the electric field. For a continuously applied DC voltage, cracks always appear on dissipation of a certain constant amount of energy. If the field is switched off before cracks appear, the observed results are shown to obey a number of empirical scaling relations, which enable us to predict the time of appearance and the number of cracks under specified conditions.
Tajkera Khatun; Tapati Dutta; Sujata Tarafdar
Effect of PCC Joint Skew on Reflective Cracking in HMA Overlays
Reflective cracking is a relatively premature distress that occurs in HMA materials overlaying cracked and jointed underlying pavements. The high concentration of stresses and strains in the vicinity of the discontinuity of the old pavement causes the cracks to reflect into the newly placed HMA overlay. While it is a common practice to use skewed transverse joints in rigid pavements to improve the latter's performance, the impact of such a practice on the cracking of a potential HMA overlay has not been examined so far. In this context, this study investigates the effect of using skewed transverse joints in rigid pavements on reflective cracking development in the HMA overlay. Advanced three-dimensional Finite Element models including viscoelastic material properties for the HMA overlay, 3D beam modeling of dowel bars, non-uniform tire-pavement contact stresses, friction interfaces, and infinite boundary elements were constructed for both normal and skewed transverse joints using ABAQUS v-6.11. The potential for reflective cracking was monitored through the fracture mechanics J-integral parameter. Results obtained show, among other things, that the practice of skewing transverse joints increases the potential for reflective cracking development in the asphalt concrete overlay.
Ziad G. Ghauch
Wireless Networking to Support Data and Voice Communication Using Spread Spectrum Technology in The Physical Layer
Wireless networking is rapidly growing and becomes an inexpensive technology which allows multiple users to simultaneously access the network and the internet while roaming about the campus. In the present work, the software development of a wireless LAN(WLAN) is highlighted. This WLAN utilizes direct sequence spread spectrum (DSSS) technology at 902MHz RF carrier frequency in its physical layer. Cost effective installation and antijaming property of spread spectrum technology are the major advantages of this work.
Dhar, Sourav
Crack growth rates of nickel alloy welds in a PWR environment.
In light water reactors (LWRs), vessel internal components made of nickel-base alloys are susceptible to environmentally assisted cracking. A better understanding of the causes and mechanisms of this cracking may permit less conservative estimates of damage accumulation and requirements on inspection intervals. A program is being conducted at Argonne National Laboratory to evaluate the resistance of Ni alloys and their welds to environmentally assisted cracking in simulated LWR coolant environments. This report presents crack growth rate (CGR) results for Alloy 182 shielded-metal-arc weld metal in a simulated pressurized water reactor (PWR) environment at 320 C. Crack growth tests were conducted on 1-T compact tension specimens with different weld orientations from both double-J and deep-groove welds. The results indicate little or no environmental enhancement of fatigue CGRs of Alloy 182 weld metal in the PWR environment. The CGRs of Alloy 182 in the PWR environment are a factor of {approx}5 higher than those of Alloy 600 in air under the same loading conditions. The stress corrosion cracking for the Alloy 182 weld is close to the average behavior of Alloy 600 in the PWR environment. The weld orientation was found to have a profound effect on the magnitude of crack growth: cracking was found to propagate faster along the dendrites than across them. The existing CGR data for Ni-alloy weld metals have been compiled and evaluated to establish the effects of key material, loading, and environmental parameters on CGRs in PWR environments. The results from the present study are compared with the existing CGR data for Ni-alloy welds to determine the relative susceptibility of the specific Ni-alloy weld to environmentally enhanced cracking.
Alexandreanu, B.; Chopra, O. K.; Shack, W. J.; Energy Technology
Studies on the disbonding initiation of interfacial cracks.
With the continuing trend of decreasing feature sizes in flip-chip assemblies, the reliability tolerance to interfacial flaws is also decreasing. Small-scale disbonds will become more of a concern, pointing to the need for a better understanding of the initiation stage of interfacial delamination. With most accepted adhesion metric methodologies tailored to predict failure under the prior existence of a disbond, the study of the initiation phenomenon is open to development and standardization of new testing procedures. Traditional fracture mechanics approaches are not suitable, as the mathematics assume failure to originate at a disbond or crack tip. Disbond initiation is believed to first occur at free edges and corners, which act as high stress concentration sites and exhibit singular stresses similar to a crack tip, though less severe in intensity. As such, a 'fracture mechanics-like' approach may be employed which defines a material parameter--a critical stress intensity factor (K{sub c})--that can be used to predict when initiation of a disbond at an interface will occur. The factors affecting the adhesion of underfill/polyimide interfaces relevant to flip-chip assemblies were investigated in this study. The study consisted of two distinct parts: a comparison of the initiation and propagation phenomena and a comparison of the relationship between sub-critical and critical initiation of interfacial failure. The initiation of underfill interfacial failure was studied by characterizing failure at a free-edge with a critical stress intensity factor. In comparison with the interfacial fracture toughness testing, it was shown that a good correlation exists between the initiation and propagation of interfacial failures. Such a correlation justifies the continuing use of fracture mechanics to predict the reliability of flip-chip packages. The second aspect of the research involved fatigue testing of tensile butt joint specimens to determine lifetimes at sub-critical load levels. The results display an interfacial strength ranking similar to that observed during monotonic testing. The fatigue results indicate that monotonic fracture mechanics testing may be an adequate screening tool to help predict cyclic underfill failure; however lifetime data is required to predict reliability.
McAdams, Brian J. (Lehigh University, Bethlehem, PA); Pearson, Raymond A. (Lehigh University, Bethlehem, PA)
Coolant Sub-Channel and Smeared-Cracking Models in BISON | Department of
Coolant Sub-Channel and Smeared-Cracking Models in BISON Coolant Sub-Channel and Smeared-Cracking Models in BISON Coolant Sub-Channel and Smeared-Cracking Models in BISON January 29, 2013 - 10:45am Addthis Coolant Sub-Channel and Smeared-Cracking Models in BISON A single-pin coolant sub-channel model was implemented in BISON, the pin-scale simulation code. This enables BISON to compute the heat transfer coefficient and coolant temperature as a function of axial position along the fuel pin (rather than requiring this information to be supplied by the user). At present, the model is only applicable to pressurized water reactor coolant conditions, but modifications to include boiling water reactor (BWR) coolant conditions are in progress. A preliminary UO2 thermal and irradiation creep model has been implemented in BISON and is
Interpretation of warm prestress-induced fracture toughness based on crack-tip constraint
This study explores the possibility of using J-Q-related crack-tip constraint concepts to provide a basis for both the interpretation of warm prestress (WPS)-induced fracture toughness and their transferability to structural applications. A finite-element boundary-layer formulation based on small-scale yielding (SSY), remote mode I K-dominant assumptions is adopted. Effects of WPS-induced crack-tip constraint are quantified in terms of deviation in either the opening-mode or the mean stress component of the WPS crack-tip fields relative to the reference K-dominant SSY state associated with monotonic-loading conditions. Over the range of WPS load-paths considered the WPS-induced crack-tip constraint closely resembles a spatially varying hydrostatic stress field. Interpretation and transferability of WPS fracture toughness under SSY conditions are specified in terms of the unload and reload ratio.
Shum, D.K.M.
Integral identities for a semi-infinite interfacial crack in 2D and 3D elasticity
The paper is concerned with the problem of a semi-infinite crack at the interface between two dissimilar elastic half-spaces, loaded by a general asymmetrical system of forces distributed along the crack faces. On the basis of the weight function approach and the fundamental reciprocal identity (Betti formula), we formulate the elasticity problem in terms of singular integral equations relating the applied loading and the resulting crack opening. Such formulation is fundamental in the theory of elasticity and extensively used to solve several problems in linear elastic fracture mechanics (for instance various classic crack problems in homogeneous and heterogeneous media). This formulation is also crucial in important recent multiphysics applications, where the elastic problem is coupled with other concurrent physical phenomena. A paradigmatic example is hydraulic fracturing, where the elasticity equations are coupled with fluid dynamics.
Andrea Piccolroaz; Gennady Mishuris
Piccolroaz, Andrea
SLAC National Accelerator Laboratory - BaBar Data Hint at Cracks...
Press Release Archive BaBar Data Hint at Cracks in the Standard Model June 18, 2012 Menlo Park, Calif. - Recently analyzed data from the BaBar experiment may suggest possible flaws...
Prediction of crack propagation paths in the unit cell of SOFC stacks
Planar Solid Oxide Fuel Cells (SOFC) stacks are multi-material layered systems with different thermo-mechanical properties. Due to their severe thermal loading, these layers have to meet high demands to preserve their mechanical integrity without initiation and propagation of fracture. Here, we focus on a typical unit cell of the stack which consists of positive electrode-electrolyte-negative electrode (PEN). Based on the mechanical properties of each layer and their interfaces, an energy criterion as a function of crack length is used for the prediction of possible crack extensions in the PEN. This criterion is a pure local criterion, independent of applied loads and geometry of the specimen. An analysis of the competition between crack deflections in the interfaces and crack penetration in layers is presented.
Joulaee, N.; Makradi, A.; Ahzi, Said; Khaleel, Mohammad A.; Koeppel, Brian J.
Effects of thermal aging on Stress Corrosion Cracking and mechanical properties of stainless steel weld metals
Stress Corrosion Cracking (SCC) in and around primary loop piping welds in Boiling Water Reactors has been observed worldwide as plants continue to operate at temperatures and pressures near 2880C (5500F) and 6.9 MPa (1000 ...
Hixon, Jeff
An Overview of Stress Cracking of Pipeline Steels in Near-neutral ...
Abstract Scope, Stress cracking of pipeline steels in near-neutral pH has remained a virile integrity risk for oil and gas pipelines. Although it was termed as stress�...
The stress corrosion crack growth response of three extruded alloy 690 CRDM tube heats was investigated in several thermomechanical conditions. Extremely low propagation rates (< 1 x 10{sup -9} mm/s) were observed under constant stress intensity factor (K) loading at 325-350 C in the as-received, thermally treated (TT) materials despite using a variety of transitioning techniques. Post-test observation of the crack-growth surfaces revealed only isolated intergranular (IG) cracking. One-dimensional cold rolling to 17% reduction and testing in the S-L orientation did not promote enhanced stress corrosion rates. However, somewhat higher propagation rates were observed in a 30% cold-rolled alloy 690TT specimen tested in the T-L orientation. Cracking of the cold-rolled material was promoted on grain boundaries oriented parallel to the rolling plane with the % IG increasing with the amount of cold rolling.
Toloczko, Mychailo B.; Bruemmer, Stephen M.
Influence of Cerium on Stress Corrosion Cracking in AZ91D
This paper considers the effect of cerium additions on the stress corrosion cracking in the Mg-Al-Zn alloy AZ91D. The two dominant phases in the AZ91D�...
Stress intensity magnification factors for fully circumferential cracks in valve bodies (thick cylinders)
The stress intensity solutions presented herein were obtained using an energy method in conjunction with a two-dimensional finite element program in order to explicitly account for curvature effect for fully circumferential cracks. The magnification factors for a specific crack depth were calculated by successively loading the crack surface by a uniform, linear, quadratic, and a cubic loading distribution. The magnification factors can be used to calculate the stress intensity factors by superposition method. The functions for each load condition in terms of radius to thickness ratio (R/t) and a fractional distance in terms of crack depth to thickness ratio (a/t) were developed. The validity of these functions is R/t = 1.5 to 10.0 and for 0.0125 {le} a/t {le} 0.8125. The functions agree to within 1% of the finite elements solutions for most magnification factors.
Toor, P.M.
Remarks on the energy release rate for an antiplane moving crack in couple stress elasticity
This paper is concerned with the steady-state propagation of an antiplane semi-infinite crack in couple stress elastic materials. A distributed loading applied at the crack faces and moving with the same velocity of the crack tip is considered, and the influence of the loading profile variations and microstructural effects on the dynamic energy release rate is investigated. The behaviour of both energy release rate and maximum total shear stress when the crack tip speed approaches the critical speed (either that of the shear waves or that of the Rayleigh waves) is studied. The limit case corresponding to vanishing characteristic scale lengths is addressed both numerically and analytically by means of a comparison with classical elasticity results.
L. Morini; A. Piccolroaz; G. Mishuris
P wave anisotropy, stress, and crack distribution at Coso geothermal field,
wave anisotropy, stress, and crack distribution at Coso geothermal field, wave anisotropy, stress, and crack distribution at Coso geothermal field, California Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Journal Article: P wave anisotropy, stress, and crack distribution at Coso geothermal field, California Details Activities (1) Areas (1) Regions (0) Abstract: A new inversion method for P wave anisotropy (Wu and Lees, 1999a) has been applied to high-precision, microseismic traveltime data collected at Coso geothermal region, California. Direction-dependent P wave velocity and thus its perturbation, are represented by a symmetric positive definite matrix A instead of a scalar. The resulting anisotropy distribution is used to estimate variations in crack density, stress distribution and permeability within the producing geothermal field. A circular dome-like
Repair and Replacement Applications Center: Stress Corrosion Cracking in Closed Cooling Water Systems
The results of a recent EPRI project "Stress Corrosion Cracking in PWR and BWR Closed Cooling Water Systems," (EPRI Report 1009721, October 2004) indicated that approximately 10 of 143 light water reactor (LWR) plants surveyed had through-wall leaks in carbon steel piping in their closed cooling water (CCW) systems. The root cause of this leakage was intergranular stress corrosion cracking. Since there has not been extensive non-destructive testing in these systems, it is likely that the incidence rate o...
Root Causes of Circumferential Cracking in Waterwalls of Supercritical Units: State-of-Knowledge
Circumferential cracking on the waterwalls has again become a significant problem for many supercritical units, especially with the implementation of low-NOx systems. Damage typically consists of multiple, parallel cracks perpendicular to the longitudinal axis of the tube and to the direction of maximum tensile stress. There can be numerous potential causes, and the choice of the appropriate control strategy will depend on identifying the underlying cause(s) for a particular outbreak of damage. This repo...
Development of a Thin Film Sensor for Detecting Initiation of Stress Corrosion Cracks in Stainless Steels
The study of initiation of intergranular stress corrosion cracking (IGSCC) has been hindered by lack of techniques to detect small cracks ranging in depth from sub-micron to several microns. The present investigation's main objective is to develop a thin film sample suitable for detecting and studying initiation of IGSCC in sensitized austenitic stainless steel. Two approaches are being investigated to produce thin films of stainless steel: pulse laser deposition (PLD) of ultrathin films (20-150 nm) usin...
Program on Technology Innovation: Development of Thin-Film Sensors to Detect Stress Corrosion Crack Initiation
A great amount of effort has been expended measuring stress corrosion crack (SCC) growth rates and investigating the mechanisms of SCC propagation. By contrast, relatively little effort has been devoted to studies of SCC initiation. The small amount of work on SCC initiation is due, in part, to the difficulty in investigating this phase of cracking. The main objective of the present investigation is to develop a thin-film sensor suitable for detecting and studying the initiation of intergranular stress c...
Assessment of Nondestructive Evaluation Methods and Analytical Procedures for Thick-Section Component Cracking
A significant concern for owners and operators, damage in the form of cracking in thick-section components (valves, casings, headers, and so on) in fossil fuel�fired boilers continues to be observed. With increased cyclic duty and the fast startups associated with combined-cycle plants, such damage will remain a prevalent industry problem. Specifically, the concerns for continued operation of cracked thick-section components arise from the uncertainties associated with the nondestructive ...
Stress Corrosion Cracking Resistance of Weld Metals 182, 72, and 308L
Intergranular stress corrosion cracking (IGSCC) has occurred in alloy 182 weld metal in operating BWRs. This study compares the propagation behavior of IGSCC for nickel-base weld metal, alloy 182, with two other weld metals: type 308L stainless steel and a high-chromium nickel-base BWR candidate, alloy 72. Results indicate that weld metal 72 is more stress corrosion crack (SCC) resistant than either weld metals 182 or type 308L.
Stress Corrosion Cracking Initiation Model for Stainless Steel and Nickel Alloys
This report provides a quantitative framework or model of general applicability in an engineering evaluation of stress corrosion cracking (SCC) initiation, including initial short crack growth, which accounts for the varied effects of cold work (CW) on SCC susceptibility. The microstructural impact of CW is accounted for through the material�s strength and strain-hardening response. CW generally acts as an accelerant in SCC. Both the surface-layer-limited cold work and the through-thickness condition nee...
Program on Technology Innovation: A Mechanistic Basis for Irradiation Assisted Stress Corrosion Cracking
Irradiation-assisted stress corrosion cracking (IASCC) refers to intergranular stress corrosion cracking that is accelerated under the action of irradiation in light water reactor core components. It is referred to as �assisted� because irradiation enhances, or accelerates, the IGSCC process over the non-irradiated state. IASCC has been a problem in the nuclear industry for the last 40 years and continues to occur due to a lack of understanding of its underlying mechanism. It is the single most important...
Development of an LP Rotor Rim-Attachment Cracking Life Assessment Code (LPRimLife)
Most of the domestic turbine fleet has reached the 50,000-hour range of service operation. Unfortunately, above this level of operational hours, a number of turbines have begun to experience low-pressure (LP) rim-attachment cracking. A computer code developed by EPRI, LPRimLife, provides utilities with a methodology for assessing the remaining life of LP rim attachments with known or suspected cracking.
Understanding the Interaction Between Localized Deformation in Materials and Environmentally Assisted Cracking
This report sets out to develop an understanding of the interaction between localized mechanical deformation in reactor structural materials (such as nickel-base alloys, austenitic stainless steels, or carbon and low-alloy steels) and their susceptibility to degradation by environmentally assisted cracking (EAC) after long-term exposure to light water reactor coolant. The main emphasis is on stress corrosion cracking (SCC), with and without the influence of irradiation, in the pressurized water reactor (...
Methodology for extracting local constants from petroleum cracking flows
A methodology provides for the extraction of local chemical kinetic model constants for use in a reacting flow computational fluid dynamics (CFD) computer code with chemical kinetic computations to optimize the operating conditions or design of the system, including retrofit design improvements to existing systems. The coupled CFD and kinetic computer code are used in combination with data obtained from a matrix of experimental tests to extract the kinetic constants. Local fluid dynamic effects are implicitly included in the extracted local kinetic constants for each particular application system to which the methodology is applied. The extracted local kinetic model constants work well over a fairly broad range of operating conditions for specific and complex reaction sets in specific and complex reactor systems. While disclosed in terms of use in a Fluid Catalytic Cracking (FCC) riser, the inventive methodology has application in virtually any reaction set to extract constants for any particular application and reaction set formulation. The methodology includes the step of: (1) selecting the test data sets for various conditions; (2) establishing the general trend of the parametric effect on the measured product yields; (3) calculating product yields for the selected test conditions using coupled computational fluid dynamics and chemical kinetics; (4) adjusting the local kinetic constants to match calculated product yields with experimental data; and (5) validating the determined set of local kinetic constants by comparing the calculated results with experimental data from additional test runs at different operating conditions.
Chang, Shen-Lin (Woodridge, IL); Lottes, Steven A. (Naperville, IL); Zhou, Chenn Q. (Munster, IN)
Predicting runaway reaction in a solid explosive containing a single crack
Mechanically damaged high explosive (HE) undergoing defiagration has recently been shown capable of generating combustion pressures and flame speeds dramatically in excess of those observed in undamaged HE. Flame penetration of HE cracks large enough to support the reaction zone serves to increase the burning surface area and the rate of gas production. Cracks confine the product gas, elevating the local pressure and reducing the reaction zone thickness such that the flame can enter smaller-width cracks. As the reaction zone decreases sufficiently to enter the smallest cracks, the flame surface area will grow appreciably, rapidly pressurizing the cracks. This runaway of pressure and burning area, termed combustion bootstrapping, can dramatically accelerate the combustion mode and in the most extreme cases may result in deflagration-to-detonation transition [3, 4]. The current study is intended to help predict the conditions required for the onset of reaction runaway in a narrow slot in HE. We review experiments [5] where flames were observed to propagate though a narrow slot (intended to simulate a well-formed crack) in high explosive at velocities up to 10 km/s, reaching pressures in excess of 1 kbar. Pressurization of the slot due to gas-dynamic choking is then used to predict the onset of runaway reaction. This model agrees with experimental pressure measurements of observed reaction runaway in slots.
Jackson, Scott I [Los Alamos National Laboratory; Hill, Larry G [Los Alamos National Laboratory
Fatigue-crack propagation in aluminum-lithium alloys processed by power and ingot metallurgy
Fatigue-crack propagation behavior in powder-metallurgy (P/M) aluminum-lithium alloys, namely, mechanically-alloyed (MA) Al-4.0Mg-1.5Li-1.1C-0.80{sub 2} (Inco 905-XL) and rapid-solidification-processed (RSP) Al-2.6Li-1.0Cu-0.5Mg-0.5Zr (Allied 644-B) extrusions, has been studied, and results compared with data on an equivalent ingot-metallurgy (I/M) Al-Li alloy, 2090-T81 plate. Fatigue-crack growth resistance of the RSP Al-Li alloy is found to be comparable to the I/M Al-Li alloy; in contrast, crack velocities in MA 905-XL extrusions are nearly three orders of magnitude faster. Growth-rate response in both P/M Al-Li alloys, however, is high anisotropic. Results are interpreted in terms of the microstructural influence of strengthening mechanism, slip mode, grain morphology and texture on the development of crack-tip shielding from crack-path deflection and crack closure. 14 refs., 7 figs., 2 tabs.
Venkateswara Rao, K.T.; Ritchie, R.O. (Lawrence Berkeley Lab., CA (United States)); Kim, N.J. (Pohang Inst. of Science and Technology (Korea, Republic of)); Pizzo, P.P. (San Jose State Univ., CA (United States))
Effects of hydrogen on electropotential monitoring of stress corrosion crack growth
Electropotential monitoring (EPM) has a crack growth measurement resolution that is an order of magnitude greater than methods that rely on crack mouth opening displacement. However, two phenomena have been identified that compromise the accuracy of the EPM technique. Coolant hydrogen concentrations above those needed to chemically reduce nickel oxide to metallic nickel cause EPM to underestimate the true crack length. The metallic nickel provides an electrical conduction path at contact points across the irregular crack surface thereby lowering the EPM potential. The coolant hydrogen concentration at which this reduction occurs is temperature dependent and correlates with an abrupt decrease in the rate of SCC crack growth. It was also found that EPM can indicate large crack growth when none actually exists. At temperatures > 315 C (600 F) the electrical resistivity of mill annealed Alloy 600 increased by as much as 5% in a period of weeks or months. Each 1% increase in resistivity results in a bias in the EPM indicated cracklength of about 0.2 mm (0.008 inches). Smaller changes in the electrical resistivity of other alloys have been measured which rank as EN52> X-750> 304SS> nickel. It has been shown that these resistivity changes occur during exposure to high temperature water or inert gas. Strategies to minimize the effects of these two phenomena on EPM measurement are discussed.
Thompson, C.D.; Carey, D.M.; Perazzo, N.L.
The effect of aqueous environments upon the initiation and propagation of fatigue cracks in low-alloy steels
The effect of elevated temperature aqueous environments upon the initiation and propagation of fatigue cracks in low-alloy steels is discussed in terms of the several parameters which influence such behavior. These parameters include water chemistry, impurities within the steels themselves, as well as factors such as the water flow rate, loading waveform and loading rates. Some of these parameters have similar effects upon both crack initiation and propagation, while others exhibit different effects in the two stages of cracking. In the case of environmentally-assisted crack (EAC) growth, the most important impurities within the steel are metallurgical sulfide inclusions which dissolve upon contact with the water. A ``critical`` concentration of sulfide ions at the crack tip can then induce environmentally-assisted cracking which proceeds at significantly increased crack growth rates over those observed in air. The occurrence, or non-occurrence, of EAC is governed by the mass-transport of sulfide ions to and from the crack-tip region, and the mass-transport is discussed in terms of diffusion, ion migration, and convection induced within the crack enclave. Examples are given of convective mass-transport within the crack enclave resulting from external free stream flow. The initiation of fatigue cracks in elevated temperature aqueous environments, as measured by the S-N fatigue lifetimes, is also strongly influenced by the parameters identified above. The influence of sulfide inclusions does not appear to be as strong on the crack initiation process as it is on crack propagation. The oxygen content of the environment appears to be the dominant factor, although loading frequency (strain rate) and temperature are also important factors.
James, L.A. [Westinghouse Electric Corp., West Mifflin, PA (United States). Bettis Atomic Power Lab.; Van Der Sluys, W.A. [Babcock and Wilcox Co., Alliance, OH (United States)
Simultaneous boiling and spreading of liquefied petroleum gas on water. Final report, December 12, 1978-March 31, 1981
An experimental and theoretical investigation was carried out to study the boiling and spreading of liquid nitrogen, liquid methane and liquefied petroleum gas (LPG) on water in a one-dimensional configuration. Primary emphasis was placed on the LPG studies. Experimental work involved the design and construction of a spill/spread/boil apparatus which permitted the measurement of spreading and local boil-off rates. With the equations of continuity and momentum transfer, a mathematical model was developed to describe the boiling-spreading phenomena of cryogens spilled on water. The model accounted for a decrease in the density of the cryogenic liquid due to bubble formation. The boiling and spreading rates of LPG were found to be the same as those of pure propane. An LPG spill was characterized by the very rapid and violent boiling initially and highly irregular ice formation on the water surface. The measured local boil-off rates of LPG agreed reasonably well with theoretical predictions from a moving boundary heat transfer model. The spreading velocity of an LPG spill was found to be constant and determined by the size of the distributor opening. The maximum spreading distance was found to be unaffected by the spilling rate. These observations can be explained by assuming that the ice formation on the water surface controls the spreading of LPG spills. While the mathematical model did not predict the spreading front adequately, it predicted the maximum spreading distance reasonably well.
Chang, H.R.; Reid, R.C.
MacroscoMacroscopic Cracking Determination in LaBS Glasspic Cracking Determination in LaBS Glass
The DOE/EM plans to conduct the Plutonium Vitrification Project at the Savannah River Site (SRS). An important part of this project is to reduce the attractiveness of the plutonium by fabricating a plutonium glass form and immobilizing the Pu form within the high level waste (HLW) glass prepared in the Defense Waste Processing Facility (DWPF). This requires that a project schedule that is consistent with EM plans for DWPF and cleanup of the SRS be developed. Critical inputs to key decisions in the vitrification project schedule are near-term data that will increase confidence that the lanthanide borosilicate (LaBS) glass product is suitable for disposal in the Yucca Mountain Repository. A workshop was held on April 28, 2005 at Bechtel SAIC Company (BSC) facility in Las Vegas, NV to define the near term data needs. Dissolution rate data and the fate of plutonium oxide and the neutron absorbers during the dissolution process were defined as key data needs. A suite of short-term tests were defined at the workshop to obtain the needed data. The objectives of these short-term tests are to obtain data that can be used to show that the dissolution rate of a LaBS glass is acceptable and to show that the extent of Pu separation from neutron absorbers, as the glass degrades and dissolves, is not likely to lead to criticality concerns. An additional data need was identified regarding the degree of macroscopic cracking and/or voiding that occurs during processing of the Pu glass waste form and subsequent pouring of HLW glass in the DWPF. A final need to evaluate new frit formulations that may increase the durability of the plutonium glass and/or decrease the degree to which neutron absorbers separate from the plutonium during dissolution was identified. This task plan covers the need to evaluate the degree of macroscopic cracking and/or voiding that occurs during processing of the Vitrified Plutonium Waste Form (i.e. the can-in-canister configuration containing the vitrified Pu product). Separate task plans were developed for Pu glass performance testing of the current baseline LaBS glass composition and development of alternative frit formulations. Recent results from Pressurized Unsaturated Flow (PUF) testing showed the potential separation of Pu from Gd during the glass dissolution process [3]. Post-test analysis of the LaBS glass from a 6-year PUF test showed a region where Pu had apparently accumulated in a Pu-bearing disk-like phase that had become separated from neutron absorber (Gd). It should be noted that this testing was conducted on the early LaBS Frit A glass composition that was devoid of HfO{sub 2} as a neutron absorber. PUF testing is currently being initiated using the LaBS Frit B composition that contains HfO{sub 2}. The potential for fissile material and neutron absorber separation is a criticality risk for the repository. The surface area that is available for leaching (i.e. due to the degree of cracking or voiding within the Pu glass cylinder) is a factor in modeling the amount of fissile material and neutron absorber released during the dissolution process. A mathematical expression for surface area is used in the Total Systems Performance Assessment (TSPA) performed by BSC personnel. Specifically, the surface area available for leaching is being used in current external criticality assessments. The planned processing steps for producing a VPWF assembly involves processing Pu feed and LaBS frit to produce a can of Pu LaBS glass, packaging this can into a second can (i.e. bagless transfer) for removal from the glovebox processing environment, placing a series of bagless transfer cans into a DWPF canister, and pouring HLW glass into the DWPF canister to encapsulate bagless transfer cans. The objective of this task is to quantify the degree of cracking and/or voiding that will occur during the processing of the VPWF.
Marra, James
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Surfactant-assisted spreading of an oil-in-water emulsion on the surface of a liquid bath
This fluid dynamics video shows how an oil-in-water emulsion stabilized by an ionic surfactant spreads on the free surface of a layer of pure water. The spreading shows two intriguing features: a transparent area surrounding the source of oil droplets, and a fast retraction of the layer of oil droplets on itself once the source has emptied. We show that the dynamics of spreading are strongly connected to the interfacial/bulk properties of the surfactant.
Roche, Matthieu; Griffiths, Ian; Saint-Jalmes, Arnaud; Stone, Howard A
Summary of Analytical Electron Microscopy Observation of Intergranular Attack and Stress Corrosion Cracks in Alloy 600 Steam Generator Tubing
High-resolution analytical transmission electron microscopy (ATEM) can identify structures and compositions of corrosion products in attacked boundaries, cracks, and crack tips to help assess impurities that promote intergranular degradation. ATEM analyses has recently been performed on samples from Watts Bar 1 and Diablo Canyon 2 steam generator (SG) tubing and has revealed that lead (Pb) was involved in intergranular stress corrosion cracking (IGSCC). These new results in combination with previous resu...
The effect of water flow rate upon the environmentally-assisted cracking response of a low-alloy steel
Effect of water flow rate on the environmentally-assisted cracking (EAC) response of a high-sulfur ferritic steel was studied at 243C. In contrast to earlier studies with compact-type specimens, this study employed relatively large tight semi-elliptical surface cracks tested under generally linear-elastic conditions. Flow velocities parallel to the crack as low as 1.68 {minus} 1.84 m/s were effective in mitigating EAC.
James, L.A.; Wire, G.L. [Westinghouse Electric Corp., West Mifflin, PA (United States). Bettis Atomic Power Lab.; Cullen, W.H. [Materials Engineering Associates, Lanham, MD (United States)
Welding and Repair Technology Center: Evaluation of High-Chromium Nickel-Base Welding Alloys, Resistance to Solidification Cracking - Update
One of the challenges faced by nuclear power industry engineers and managers responsible for making welding and repair decisions is selection of weld metals that have adequate resistance to stress corrosion cracking (SCC) with acceptable resistance to other forms of cracking. Continued testing and evaluation of new and enhanced high-chromium nickel-base filler metals is important to understanding the influence of slight composition changes on sensitivity to known cracking mechanisms and general ...
Resistance of Alloy 600 and Alloy 690 Tubing to Stress Corrosion Cracking in Environments With and Without Lead
Recent examinations of degraded steam generator tubes pulled from several plants suggest possible lead (Pb) involvement in intergranular attack/stress corrosion cracking (IGA/SCC). EPRI sponsored this research program to determine the factors influencing lead stress corrosion cracking (PbSCC) in Alloy 600 and Alloy 690 steam generator tubes. The most severe cracking condition occurred at the open circuit corrosion potential, contrary to previous testing results. A film rupture/anodic dissolution model, w...
Environmentally assisted cracking of nickel anode substrates in Li/SOCl{sub 2} cells: An engineering approach
Intergranular environmentally assisted cracking (EAC) of Ni anode substrates is likely to occur in a large proportion of Li/SOCl{sub 2} cells, but it is not generally detected because in the majority of cases it does not lead to catatrophic failure. However, EAC could become a problem for applications requiring continuous power with high reliability for 10--15 years. In the present work, we determine why simple galvanic couple constant-strain tests do not produce cracking, and introduce a constant strain test that does produce cracking. Objective of this investigation is to determine the stress threshold for cracking as a function of Ni composition and microstructure.
Cieslak, W.R.; Weigand, D.E.; Buchheit, R.G.
Hydrodesulfurization of Fluid Catalytic Cracking Decant Oils for the Production of Low-sulfur Needle Coke Feedstocks.
??Needle coke, produced by the delayed coking of fluid catalytic cracking decant oils, is the primary filler used in the production of graphite electrodes. The� (more)
Wincek, Ronald
Discrete Event Front-tracking Simulation of a Physical Fire-spread Model
Simulation of moving interfaces such as a fire front usually requires resolution of a large-scale and detailed domain. Such computing involves the use of supercomputers to process the large amount of data and calculations. This limitation is mainly due ... Keywords: DEVS, asynchronous, discrete events, envelope, fire spread, flame, forest, front tracking, interface, simulation
Jean-Baptiste Filippi; Fr�d�ric Morandini; Jacques Henri Balbi; David Rc Hill
Cytoskeletal reorganization induced by engagement of the NG2 proteoglycan leads to cell spreading and migration
Cells expressing the NG2 proteoglycan can attach, spread, and migrate on surfaces coated with NG2 mAbs, demonstrating that engagement of NG2 can trigger the cytoskeletal rearrangements necessary for changes in cell morphology and motility. Engagement of different epitopes of the proteoglycan results in distinct forms of actin reorganization. On mAb D120, the cells contain radial actin spikes characteristic of filopodial extension, whereas on mAb N143, the cells contain cortical actin bundles characteristic of lamellipodia. Cells that express NG2 variants lacking the transmembrane and cytoplasmic domains are unable to spread or migrate on NG2 mAb-coated surfaces, indicating that these portions of the molecule are essential for NG2-mediated signal transduction. Cells expressing an NG2 variant lacking the C-terminal half of the cytoplasmic domain can still spread normally on mAbs D120 and N143, suggesting that the membraneproximal cytoplasmic segment is responsible for this process. In contrast, this variant migrates poorly on mAb D120 and exhibits abnormal arrays of radial actin filaments decorated with fascin during spreading on this mAb. The C-terminal portion of the NG2 cytoplasmic domain, therefore, may be involved in regulating molecular events that are crucial for cell motility.
Xuexun Fang; Michael A. Burg; Diana Barritt; Akiko Nishiyama; William B. Stallcup; Thomas D. Pollard
energy from the gun. It is believed that this DC energy shift is due to the use of mesh and focusingEXPERIMENTAL STUDY OF ENERGY SPREAD IN A SPACE-CHARGE DOMINATED ELECTRON BEAM * Y. Cui , Y. Zou, A Physics, University of Maryland, College Park, Maryland 20742 Abstract Characterization of beam energy
Valfells, Ágúst
Deployment Aware Modeling of Node Compromise Spread in Wireless Sensor Networks Using
emerged viruses that can spread over air interfaces, and the various broadcast protocols for transferring or commercial advantage, the ACM copyright/server notice, the title of the publication, and its date appear, and notice is given that copying is by permission of the ACM, Inc. To copy otherwise, to republish, to post
Liu, Yonghe
Neurokinin-1 enables measles virus trans-synaptic spread in neurons
Measles virus (MV), a morbillivirus that remains a significant human pathogen, can infect the central nervous system, resulting in rare but often fatal diseases, such as subacute sclerosing panencephalitis. Previous work demonstrated that MV was transmitted trans-synaptically and that, while a cellular receptor for the hemagglutinin (H) protein was required for MV entry, it was dispensable for subsequent cell-to-cell spread. Here, we explored what role the other envelope protein, fusion (F), played in trans-synaptic transport. We made the following observations: (1) MV-F expression in infected neurons was similar to that seen in infected fibroblasts; (2) fusion inhibitory peptide (FIP), an inhibitor of MV fusion, prevented both infection and spread in primary neurons; (3) Substance P, a neurotransmitter with the same active site as FIP, also blocked neuronal MV spread; and (4) both genetic deletion and pharmacological inhibition of the Substance P receptor, neurokinin-1 (NK-1), reduced infection of susceptible mice. Together, these data implicate a role for NK-1 in MV CNS infection and spread, perhaps serving as an MV-F receptor or co-receptor on neurons.
Makhortova, Nina R. [Division of Basic Science, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111 (United States); Askovich, Peter [Division of Basic Science, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111 (United States); Patterson, Catherine E. [Division of Basic Science, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111 (United States); Gechman, Lisa A. [Division of Basic Science, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111 (United States); Gerard, Norma P. [Children's Hospital, Perlmutter Laboratory, Boston, MA 02115 (United States); Rall, Glenn F. [Division of Basic Science, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111 (United States)]. E-mail: firstname.lastname@example.com
Prediction of spreading processes using a supervised self-organizing map
A novel technique is presented based on self-organizing neural networks for prediction of fertilizer distribution patterns of spreaders as a function of spreader settings and fertilizer properties. The main aim of the presented technique is to predict ... Keywords: centrifugal spreader, classification, fertilizer particles, machine settings, neural networks, physical properties, prediction, self-organizing maps, spinning disc spreader, spreading pattern
Dimitrios Moshou; Koen Deprez; Herman Ramon
A variable spread fuzzy linear regression model with higher explanatory power and forecasting accuracy
Fuzzy regression models have been applied to operational research (OR) applications such as forecasting. Some of previous studies on fuzzy regression analysis obtain crisp regression coefficients for eliminating the problem of increasing spreads for ... Keywords: Forecasting, Fuzzy inference, Fuzzy sets, Linear regression, Mathematical programming
Shih-Pin Chen; Jr-Fong Dang
Acoustic Emission and Guided Wave Monitoring of Fatigue Crack Growth on a Full Pipe Specimen
Continuous on-line monitoring of active and passive systems, structures and components in nuclear power plants will be critical to extending the lifetimes of nuclear power plants in the US beyond 60 years. Acoustic emission and guided ultrasonic waves are two tools for continuously monitoring passive systems, structures and components within nuclear power plants and are the focus of this study. These tools are used to monitor fatigue damage induced in a SA 312 TP304 stainless steel pipe specimen. The results of acoustic emission monitoring indicate that crack propagation signals were not directly detected. However, acoustic emission monitoring exposed crack formation prior to visual confirmation through the detection of signals caused by crack closure friction. The results of guided ultrasonic wave monitoring indicate that this technology is sensitive to the presence and size of cracks. The sensitivity and complexity of GUW signals is observed to vary with respect to signal frequency and path traveled by the guided ultrasonic wave relative to the crack orientation.
Meyer, Ryan M.; Cumblidge, Stephen E.; Ramuhalli, Pradeep; Watson, Bruce E.; Doctor, Steven R.; Bond, Leonard J.
R-curve and subcritical crack growth behavior at elevated temperatures in coarse grain alumina
The effect of temperature and subcritical crack growth on the R-curve of a 99.5% purity coarse grained alumina was studied using chevron-notched, short-bar specimens. Constant loading rate tests were used to measure toughness as a function of crack length and static load tests were used to measure subcritical crack growth as a function of time. It was found that the intrinsic toughness decreased monotonically from 20 to 1200 C while the bridging contribution to the R-curve remained relatively constant over this temperature range. The constant load tests at 700, 1000 and 1200 C showed that substantial subcritical crack growth occurs under static loading. Using the subcritical crack growth parameters derived from these static load tests, the effect of loading rate on R-curve measurement was predicted and compared to experiment. The predicted decrease in the magnitude of the R-curve with a decrease in over five orders of magnitude in loading rate was relatively small compared to experimental scatter.
Webb, J.E.; Jakus, K.; Ritter, J.E. [Univ. of Massachusetts, Amherst, MA (United States). Dept. of Mechanical Engineering
Subcritical Crack Growth Processes in SiC/SiC Ceramic Matrix Composites
Ceramic matrix composites have the potential to operate at high-temperatures and are, therefore being considered for a variety of advanced energy technologies such as combustor liners in land based gas turbo/generators, heat exchangers and advanced fission and fusion reactors. Ceramic matrix composites exhibit a range of crack growth mechanisms driven by a range of environmental and nuclear conditions. The crack growth mechanisms include: 1) fiber relaxation by thermal (FR) and irradiation (FIR) processes, 2) fiber stress-rupture (SR), 3) interface removal (IR) by oxidation, and 4) oxidation embrittlement (OE) resulting from glass formation including effects of glass viscosity. Analysis of these crack growth processes has been accomplished with a combination experimental/modeling effort. Dynamic, high-temperature, in situ crack growth measurements have been made in variable Ar + O2 environments while a PNNL developed model has been used to extrapolate this data and to add radiation effects. In addition to the modeling effort, a map showing these mechanisms as a function of environmental parameters was developed. This mechanism map is an effective tool for identifying operating regimes and predicting behavior. The process used to develop the crack growth mechanism map was to: 1) hypothesize and experimentally verify the operative mechanisms, 2) develop an analytical model for each mechanism, and 3) define the operating regime and boundary conditions for each mechanism. A map for SiC/SiC composites has been developed for chemical and nuclear environments as a function of temperature and time.
Jones, Russell H.; Henager, Charles H.
Cracking of simulated oil refinery off-gas over a coal char, petroleum coke, and quartz
The cracking of oil refinery off-gas, simulated with a gas mixture containing methane (51%), ethylene (21.4%), ethane (21.1%), and propane (6.5%), over a coal char, petroleum coke, and quartz, respectively, has been studied in a fixed bed reactor. The experiments were performed at temperatures between 850 and 1000{sup o}C and at atmospheric pressure. The results show that the conversions of all species considered increased with increasing temperature. Ethane and propane completely decomposed over all three bed materials in the temperature range investigated. However, the higher initial conversion rates of methane and ethylene cracking at all temperatures were observed only over the coal char and not on the petroleum coke and quartz, indicating a significant catalytic effect of the coal char on methane and ethylene cracking. Methane and ethylene conversions decreased with reaction time due to deactivation of the coal char by carbon deposition on the char surface and, in the later stage of a cracking experiment, became negative, suggesting that methane and ethylene had been formed during the cracking of ethane and propane. 16 refs., 13 figs., 2 tabs.
Yuan Zhang; Jin-hu Wu; Dong-ke Zhang [Chinese Academy of Sciences, Taiyuan (China). Institute of Coal Chemistry
Note on numerical study of the beam energy spread in NDCX-I
The kinetic energy spread (defined here as the standard deviation of the beam particle energies) sets the ultimate theoretical limit on the longitudinal compression that can be attained on NDCX-I and NDCX-II. Experimental measurements will inevitably include the real influences on the longitudinal phase space of the beam due to injector and accelerator field imperfections1. These induced energy variations may be the real limit to the longitudinal compression in an accelerator. We report on a numerical investigation of the energy spread evolution in NDCX-I; these studies do not include all the real imperfections, but rather are intended to confirm that there are no other intrinsic mechanisms (translaminar effects, transverse-longitudinal anisotropy instability, etc.) for significant broadening of the energy distribution. We have performed Warp simulations that use a realistic Marx voltage waveform which was derived from experimental measurements (averaged over several shots), a fully-featured model of the accelerating and focusing lattice, and new diagnostics for computing the local energy spread (and temperature) that properly account for linear correlations that arise from the discrete binning along each physical dimension (these capabilities reproduce and extend those of the earlier HIF code BPIC). The new diagnostics allow for the calculation of multi-dimensional maps of energy spread and temperature in 2-D axisymmetric or 3-D Cartesian space at selected times. The simulated beam-line was terminated at z = 3 m by a conducting plate, so as to approximately reproduce the experimental conditions at the entrance of the spectrometer that was used for mapping the longitudinal phase space. Snapshots of the beam projection and current, as well as the Marx waveform and history of beam kinetic energy collected at the end plate, are shown in Fig. 1. A two-dimensional axisymmetric map of energy spread from simulations of a typical NDCX-I configuration is shown in Fig. 2 (a). The energy spread starts at 0.1 eV at the source and rapidly rises to a few eV, then fluctuates between a fraction of an eV and tens of eV, ending near the exit in a range of a few eV at the outer edge of the beam to a few tens of eV near the axis. The higher value on-axis is associated with greater numerical noise there, due to the axisymmetric geometry of the calculation, resulting in poorer simulation-particle statistics at small radius. A scatter plot of the macroparticles kinetic energy (KE) versus radius (R) and longitudinal position (0.28 m < z < 3 m) colored by local energy spread is shown in Fig. 2 (b). As expected, there is a correlation of the kinetic energy with radius that is clearly visible at z = 2.8 m and vanishes at the metal plate at z = 3 m. More snapshots from simulations varying the time step, grid resolution and number of macroparticles are given in Appendix II. The macro-particles were collected at the exit plate and their kinetic energy history is plotted in Fig. 3 (left) and contrasted to an experimental measurement using a streak camera shown in Fig. 3. For some types of measurements, averaging over several pulses to improve signal-to-noise will contribute an additional spread that may not be present on any single beam pulse. The upper bound for the energy spread is in the range of a few 100 eV for the experiment while in the range of a few eV for the reported Warp simulations. The Marx voltage exhibits variations in the range of up to several hundreds of volts, playing a significant role in the experimentally measured energy spread, which may account for the difference between the experimental and the simulated bounds.
Vay, J.-L.; Seidl, P.A.; Friedman, A.
The kinetic energy spread (defined here as the standard deviation of the beam particle energies) sets the ultimate theoretical limit on the longitudinal compression that can be attained on NDCX-I and NDCX-II. Experimental measurements will inevitably include the real influences on the longitudinal phase space of the beam due to injector and accelerator field imperfections1. These induced energy variations may be the real limit to the longitudinal compression in an accelerator. We report on a numerical investigation of the energy spread evolution in NDCX-I; these studies do not include all the real imperfections, but rather are intended to confirm that there are no other intrinsic mechanisms (translaminar effects, transverse-longitudinal anisotropy instability, etc.) for significant broadening of the energy distribution. We have performed Warp simulations that use a realistic Marx voltage waveform which was derived from experimental measurements (averaged over several shots), a fully-featured model of the accelerating and focusing lattice, and new diagnostics for computing the local energy spread (and temperature) that properly account for linear correlations that arise from the discrete binning along each physical dimension (these capabilities reproduce and extend those of the earlier HIF code BPIC). The new diagnostics allow for the calculation of multi-dimensional maps of energy spread and temperature in 2-D axisymmetric or 3-D Cartesian space at selected times. The simulated beam-line was terminated at z = 3 m by a conducting plate, so as to approximately reproduce the experimental conditions at the entrance of the spectrometer that was used for mapping the longitudinal phase space. Snapshots of the beam projection and current, as well as the Marx waveform and history of beam kinetic energy collected at the end plate, are shown in Fig. 1. A two-dimensional axisymmetric map of energy spread from simulations of a typical NDCX-I configuration is shown in Fig. 2 (a). The energy spread starts at 0.1 eV at the source and rapidly rises to a few eV, then fluctuates between a fraction of an eV and tens of eV, ending near the exit in a range of a few eV at the outer edge of the beam to a few tens of eV near the axis. The higher value on-axis is associated with greater numerical noise there, due to the axisymmetric geometry of the calculation, resulting in poorer simulation-particle statistics at small radius. A scatter plot of the macroparticles kinetic energy (KE) versus radius (R) and longitudinal position (0.28 m energy spread is shown in Fig. 2 (b). As expected, there is a correlation of the kinetic energy with radius that is clearly visible at z = 2.8 m and vanishes at the metal plate at z = 3 m. More snapshots from simulations varying the time step, grid resolution and number of macroparticles are given in Appendix II. The macro-particles were collected at the exit plate and their kinetic energy history is plotted in Fig. 3 (left) and contrasted to an experimental measurement using a streak camera shown in Fig. 3. For some types of measurements, averaging over several pulses to improve signal-to-noise will contribute an additional spread that may not be present on any single beam pulse. The upper bound for the energy spread is in the range of a few 100 eV for the experiment while in the range of a few eV for the reported Warp simulations. The Marx voltage exhibits variations in the range of up to several hundreds of volts, playing a significant role in the experimentally measured energy spread, which may account for the difference between the experimental and the simulated bounds.
Physics-Based Stress Corrosion Cracking Component Reliability Model cast in
Physics-Based Stress Corrosion Cracking Component Reliability Model Physics-Based Stress Corrosion Cracking Component Reliability Model cast in an R7-Compatible Cumulative Damage Framework Physics-Based Stress Corrosion Cracking Component Reliability Model cast in an R7-Compatible Cumulative Damage Framework The Risk-Informed Safety Margin Characterization (RISMC) pathway is a set of activities defined under the U.S. Department of Energy Light Water Reactor Sustainability Program. The overarching objective of RISMC is to support plant life-extension decision-making by providing a state-of-knowledge characterization of safety margins in key systems, structures, and components (SSCs). The methodology emerging from the RISMC pathway is not a conventional probabilistic risk assessment (PRA)-based one; rather, it relies on a reactor systems simulation framework in which
Cracking Molecular Structures with Bright Lights - and a Few Good Eggs |
Cracking Molecular Structures with Bright Lights - and a Few Good Cracking Molecular Structures with Bright Lights - and a Few Good Eggs Cracking Molecular Structures with Bright Lights - and a Few Good Eggs June 22, 2012 - 11:04am Addthis This rendering shows a lysozyme structural model against its X-ray diffraction pattern from SLACâs Linac Coherent Light Source (LCLS), a powerful X-ray laser facility. Researchers have achieved high-resolution images of these simple biomolecules using advanced crystallography at LCLS. | Photo by Anton Barty/DESY This rendering shows a lysozyme structural model against its X-ray diffraction pattern from SLAC's Linac Coherent Light Source (LCLS), a powerful X-ray laser facility. Researchers have achieved high-resolution images of these simple biomolecules using advanced crystallography at LCLS.
Evaluation of cracking in the 241-AZ tank farm ventilation line at the Hanford Site
In the period from April to October of 1988, a series of welding operations on the outside of the AZ Tank Farm ventilation line piping at the Hanford Site produced unexpected and repeated cracking of the austenitic stainless steel base metal and of a seam weld in the pipe. The ventilation line is fabricated from type 304L stainless steel pipe of 24 inch diameter and 0.25 inch wall thickness. The pipe was wrapped in polyethylene bubble wrap and buried approximately 12 feet below grade. Except for the time period between 1980 and 1987, impressed current cathodic protection has been applied to the pipe since its installation in 1974. The paper describes the history of the cracking of the pipe, the probable cracking mechanisms, and the recommended future action for repair/replacement of the pipe.
Diffraction coefficients of a semi-infinite planar crack embedded in a transversely-isotropic space
We have considered a semi-infinite crack embedded in a transversely isotropic medium and studied two special cases, one, in which the axis of symmetry is normal to the crack face and the wave incidence is arbitrary and another, in which the axis lies in the crack plane normal to the edge and the incident wave vector is also normal to the edge. The problem is of interest in Non-Destructive Evaluation, because austenitic steels that are found in claddings and other welds in the nuclear reactors are often modeled as transversely isotropic. In both of cases, we have expressed the scattered field in a closed form and computed the corresponding diffraction coefficients.
A. Gautesen; V. Zernov; L. Fradkin
Stress corrosion cracking of type 304L stainless steel core shroud welds.
Microstructural analyses by advanced metallographic techniques were conducted on mockup welds and a cracked BWR core shroud weld fabricated from Type 304L stainless steel. heat-affected zones of the shroud weld and mockup shielded-metal-arc welds were free of grain-boundary carbide, martensite, delta ferrite, or Cr depletion near grain boundaries. However, as a result of exposure to welding fumes, the heat-affected zones of the welds were significantly contaminated by fluorine and oxygen which migrate to grain boundaries. Significant oxygen contamination promotes fluorine contamination and suppresses classical thermal sensitization, even in Type 304 steels. Results of slow-strain-rate tensile tests indicate that fluorine exacerbates the susceptibility of irradiated steels to intergranular stress corrosion cracking. These observations, combined with previous reports on the strong influence of weld flux, indicate that oxygen and fluorine contamination and fluorine-catalyzed stress corrosion play a major role in cracking of Type 304L stainless steel core shroud welds.
Chung, H. M.; Park, J.-H.; Sanecki, J. E.; Zaluzec, N. J.; Yu, M. S.; Yang, T. T.
Method and apparatus for detecting external cracks from within a metal tube
A method and tool using a continuous electromagnetic wave from a transverse magnetic-dipole source with a coaxial electric-dipole receiver is described for the detection of external sidewall cracks and other anomalies in boiler tubes and other enclosures. The invention utilizes the concept of radar backscatter rather than eddy-currents or ultrasound, which are sometimes used in prior art crack-detection methods. A numerical study of the distribution of the fields shows that the direct transmission from the source to the receiver is reduced from that in free space. Further, if the diameter of the receiver dipole is made sufficiently small, it should be possible to detect cracks with a scattering loss of up to -40 dB in thin-walled boiler tubes.
Caffey, Thurlow W. H. (Albuquerque, NM)
The Hanford reservation Tank Farms in Washington State has 177 underground storage tanks that contain approximately 50 million gallons of liquid legacy radioactive waste from cold war plutonium production. These tanks will continue to store waste until it is treated and disposed. These nuclear wastes were converted to highly alkaline pH wastes to protect the carbon steel storage tanks from corrosion. However, the carbon steel is still susceptible to localized corrosion and stress corrosion cracking. The waste chemistry varies from tank to tank, and contains various combinations of hydroxide, nitrate, nitrite, chloride, carbonate, aluminate and other species. The effect of each of these species and any synergistic effects on localized corrosion and stress corrosion cracking of carbon steel have been investigated with electrochemical polarization, slow strain rate, and crack growth rate testing. The effect of solution chemistry, pH, temperature and applied potential are all considered and their role in the corrosion behavior will be discussed.
Method for cracking hydrocarbon compositions using a submerged reactive plasma system
A method for cracking a liquid hydrocarbon composition (e.g. crude oil) to produce a cracked hydrocarbon product. A liquid hydrocarbon composition is initially provided. An electrical arc is generated directly within the hydrocarbon composition so that the arc is entirely submerged in the composition. Arc generation is preferably accomplished using a primary and secondary electrode each having a first end submerged in the composition. The first ends of the electrodes are separated from each other to form a gap therebetween. An electrical potential is then applied to the electrodes to generate the arc within the gap. A reactive gas is thereafter delivered to the arc which forms a bubble around the arc. Gas delivery may be accomplished by providing a passageway through each electrode and delivering the gas through the passageways. The arc and gas cooperate to produce a plasma which efficiently cracks the hydrocarbon composition.
Kong, Peter C. (Idaho Falls, ID)
A method is described for cracking a liquid hydrocarbon composition (e.g. crude oil) to produce a cracked hydrocarbon product. A liquid hydrocarbon composition is initially provided. An electrical arc is generated directly within the hydrocarbon composition so that the arc is entirely submerged in the composition. Arc generation is preferably accomplished using a primary and secondary electrode each having a first end submerged in the composition. The first ends of the electrodes are separated from each other to form a gap there between. An electrical potential is then applied to the electrodes to generate the arc within the gap. A reactive gas is thereafter delivered to the arc which forms a bubble around the arc. Gas delivery may be accomplished by providing a passageway through each electrode and delivering the gas through the passageways. The arc and gas cooperate to produce a plasma which efficiently cracks the hydrocarbon composition. 6 figs.
Kong, P.C.
A Review of Stress Corrosion Cracking/Fatigue Modeling for Light Water
A Review of Stress Corrosion Cracking/Fatigue Modeling for Light A Review of Stress Corrosion Cracking/Fatigue Modeling for Light Water Reactor Cooling System Components A Review of Stress Corrosion Cracking/Fatigue Modeling for Light Water Reactor Cooling System Components In the United States currently there are approximately 104 operating light water reactors. Of these, 69 are pressurized water reactors (PWRs) and 35 are boiling water reactors (BWRs). In 2007, the 104 light-water reactors (LWRs) in the United States generated approximately 100 GWe, equivalent to 20% of total US electricity production. Most of the US reactors were built before 1970 and the initial design lives of most of the reactors are 40 years. It is expected that by 2030, even those reactors that have received 20-year life extension license from the US Nuclear Regulatory Commission
Supercomputers Crack Sixty-Trillionth Binary Digit of Pi-Squared |
Supercomputers Crack Sixty-Trillionth Binary Digit of Pi-Squared Supercomputers Crack Sixty-Trillionth Binary Digit of Pi-Squared Supercomputers Crack Sixty-Trillionth Binary Digit of Pi-Squared April 28, 2011 - 11:28am Addthis David H. Bailey | Photo Courtesy of Lawrence Berkely National Lab David H. Bailey | Photo Courtesy of Lawrence Berkely National Lab Linda Vu What are the key facts? Australian researchers have found the sixty-trillionth binary digit of Pi-squared. The calculation would have taken a single computer processor unit (CPU) 1,500 years to calculate, but it took just a few months on IBM's "BlueGene/P" supercomputer, which is designed to run continuously at one quadrillion calculations per second. Pi is one of the most mysterious numbers in mathematics and can never be expressed as a finite decimal number -- humanity will never have
A computational study of ethane cracking in cluster models of zeolite H-ZSM-5.
Protolytic cracking of ethane by zeolites has been studied using quantum-chemical techniques and a cluster model of the zeolite Broensted acid site. Previous computational studies have utilized small cluster models and have not accounted for the long-range effects of the zeolite lattice. These studies have found reaction barriers for cracking which are significantly higher than experimental values. In this work we used a larger zeolite cluster model containing five tetrahedral (Si, Al) atoms (denoted 5T) and searched for stationary points along one possible reaction path for cracking at the HF/6-31 G(d) level of theory. This path involves a multi-step cracking reaction, in which the proton is first transferred from the acid site to the adsorbed ethane molecule to form an ion-pair equilibrium complex. Subsequently the proton attacks the C-C bond to complete the cracking process. The activation barrier for cracking was calculated, including corrections for (i) vibrational energies at the experimental reaction temperature of 773 K; (ii) electron correlation and an extended basis set at the B3LYP/6-311+G(3df,2p) level; and (iii) the influence of the surrounding zeolite lattice in H-ZSM-5. The barrier we obtain, 53 {+-} 5 kcal/mol, is significantly smaller than previous theoretical results and is in good agreement with typical experimental values for small hydrocarbons. Work is currently in progress to extend this study by carrying out geometry optimization of these complexes using the B3LYP method of density functional theory.
Zygmunt, S. A.
A software framework for fine grain parallelization of cellular models with OpenMP: Application to fire spread
We are dealing here with the parallelization of fire spreading simulations following detailed physical experiments. The proposal presented in this paper has been tested and evaluated in collaboration with physicists to meet their requirements in terms ... Keywords: DEVS, Fire spread physical model, Open MultiProcessing (OpenMP), Software framework, Symmetric multiprocessors (SMP)
Eric Innocenti; Xavier Silvani; Alexandre Muzy; David R. C. Hill
Imprinting the memory into paste and its visualization as crack patterns in drying process
In the drying process of paste, we can imprint into the paste the order how it should be broken in the future. That is, if we vibrate the paste before it is dried, it remembers the direction of the initial external vibration, and the morphology of resultant crack patterns is determined solely by the memory of the direction. The morphological phase diagram of crack patterns and the rheological measurement of the paste show that this memory effect is induced by the plasticity of paste.
Akio Nakahara; Yousuke Matsuo
Effects of neutron irradiation on fatigue and creep-fatigue crack propagation in type 316 stainless steel at 649 degree C produced no significant effect on the crack propagation rate when compared with unirradiated steel tested at 649 degree C
The fatigue and creep-fatigue crack propagation performance of Type 316 stainless steel has been investigated following fast neutron (n) irradiation. The purpose was to evaluate the effects of neutron fluence and temperature on the crack propagation resistance and failure mode of the steel. Results are presented from fatigue tests of the annealed steel that were irradiated at 649 degree C Scanning electron microscope examination of the fracture surfaces of the tested specimens revealed that the failure mode of the specimens which exhibited increased crack propagation rates was primarily intergranular while a transgranular mode was observed for specimens with lower crack propagation rates. The results point toward a synergistic relationship between thermomechanical history, precipitate formation, and hold time effects as the responsible mechanism for the crack propagation performance.
Michel, D.J.; Smith, H.H.
Some mechanistic observations on the crack growth characteristics of pressure vessel and piping steels in PWR environment
The fatigue crack growth behavior of A533B and A508 pressure vessel steel and AISI Types 304 and 316 steels used in reactor coolant piping have been studied in a pressurized water reactor environment at 288/sup 0/C (550/sup 0/F). The influence of stress ratio (P/sub min//P/sub max/), frequency, ramp times, specimen orientation and material microstructures were included in the study. While none of the materials showed evidence of static crack growth in the environment, the ferritic steels did show an enhanced fatigue crack growth rate at test frequencies of five cycles per minute and lower. Based on fractographic examinations the enhanced growth rate is not the result of environmentally induced intergranular or cleavage modes of crack propagation. Instead, striation spacing measurements were found to agree with the macroscopic crack growth rate, demonstrating a time dependent environmental interaction which introduces a frequency dependent enhancement of the mechanically developed striations. Crack growth experiments using hold times have confirmed the absence of any superimposed contribution of static crack growth components. Fatigue crack growth tests were conducted in an environment of Hydrogen Sulfide gas to establish the contribution of hydrogen embrittlement and will also be described.
Bamford, W.H.; Moon, D.M.
Finite element analysis of grain-matrix micro-cracking in shale within the context of a multiscale modeling
, hydrofracturing, or oil shale production. Current macro- scale and multiscale models do not account simultaneouslyFinite element analysis of grain-matrix micro-cracking in shale within the context of a multiscale-cracking in shale at grain-matrix inter- faces, assuming constituents are composed of quart silt grains
Regueiro, Richard A.
Enhanced heat extraction from hot-dry-rock geothermal reservoirs due to interacting secondary thermal cracks. Final report
How the fluid circulating through the main hydraulic fracture and the thermally-induced secondary, growing, interacting cracks affects the time-varying temperature, deformations, stresses, thermal crack geometry, water flow rates through the main and thermal cracks, reservoir coolant outlet temperature, and reservoir thermal power of the cracked geothermal reservoir is investigated. First, a simplified version of the proposed hot-dry-rock reservoir is considered. A closed-form solution of the rock temperature without thermal crack was found and substituted into SAP-IV computer code to calculate the stresses. These stresses being superposed with earth stresses and fluid pressure were used in conjunction with the fracture mechanics criterion to determine the initiation of secondary thermal crack. After the initiation of secondary thermal crack, the rock temperature was then calculated by a two-dimensional heat conduction program AYER. The detailed procedures for carrying out these steps are listed. Solutions developed are applied to studying the time-varying temperature field, thermal stresses and crack geometry produced, and additional heat power generated in the reservoir. Conclusions were discussed and summarized. (MHR)
Hsu, Y.C.
Acoustic wave propagation in cracked porous rocks and application to interpreting acoustic log data in tight formations
Rocks in earth's crust usually contain both pores and cracks. Typical examples include tight sandstone and shale rocks that have low porosity but contain abundant microcracks. By extending the classic Biot's poroelastic wavetheory to include the effects of cracks
Xiaoming Tang; Xuelian Chen
Growth of geologic fractures into large-strain populations: review of nomenclature, subcritical crack growth, and some implications
. An array of initially mixed-mode (I±II) cracks will evolve under remote tensile least principal stress±network evolution. An increase in the stress corrosion index promotes joint clustering and signi®cant changes crack growth, and some implications for rock engineering R.A. Schultz* Geomechanics-Rock Fracture Group
PHYSICAL REVIEW E 84, 036104 (2011) Average crack-front velocity during subcritical fracture propagation in a heterogeneous medium
stress corrosion, diffusion, dissolution, and plasticity [1,5]. Several experimental empirical relations results in an increase in the speed of crack growth. A weak stress-sensitive regime follows wherePHYSICAL REVIEW E 84, 036104 (2011) Average crack-front velocity during subcritical fracture
Schmittbuhl, Jean
ENERGY CHANGES IN STRESSED BODIES DUE TO VOID AND CRACK J. R. Rice** and D. C. Drucker***
, and the mechanical aspects of stress corrosion cracking are discussed. INTRODUCTION A comparison is made firstENERGY CHANGES IN STRESSED BODIES DUE TO VOID AND CRACK GROWTH* J. R. Rice** and D. C. Drucker materials, and for the mechanical aspects of stress corrosion. The authors acknowledge with thei~ respective
Effect of Oxygen on the Crack Growth Behavior of V-4Cr-4Ti at 600C
Exploratory experiments were performed to evaluate the effect of oxygen on the crack growth response of V-4Cr-4Ti at 600C under constant load. Tests were run in gettered argon, argon containing 2000 ppm oxygen, and laboratory air using fatigue pre-cracked compact tension specimens. Crack growth was measured primarily by post-test fracture surface examination, but also by in-test compliance measurements. Crack growth rates measured in air and gettered argon were about 2-3x10-3 mm/h at a stress intensity factor of about 40 MPavm. The crack growth rate in argon with 2000 ppm oxygen was about 7x10-2 mm/h at the same stress intensity level. The crack growth rates were very sensitive to the stress intensity factor. Over a limited range of stress intensity values the crack growth rate in argon plus 2000 ppm oxygen appears to be power-law dependent on stress intensity with an exponent of about 8.9. The fracture mode in air and gettered argon was transgranular cleavage with 20 to 30% intergranular fracture. In the oxygenated argon environment crack growth occurred predominantly by transgranular cleavage.
Kurtz, Richard J.
An extended finite element method for hydraulic fracture propagation in deformable porous media with the cohesive crack model
In this paper, a fully coupled numerical model is developed for the modeling of the hydraulic fracture propagation in porous media using the extended finite element method in conjunction with the cohesive crack model. The governing equations, which account ... Keywords: Cohesive crack propagation, Fluid flow, Fracturing porous media, Fully coupled model, Hydraulic fracturing, XFEM
T. Mohammadnejad, A. R. Khoei
Liquid waste generated by the PUREX process for separation of nuclear materials is concentrated and stored in Type IV single-shell carbon steel tanks at the Savannah River Site (SRS). The Type IV tanks for this waste do not have cooling coils and have not undergone heat treatment to stress-relieve the tanks. After the waste is concentrated by evaporation, it becomes very alkaline and can cause stress corrosion cracking (SCC) and pitting corrosion of the tank materials. SRS has experienced leakage from non-stress-relieved waste tanks constructed of A285 carbon steel and pitting of A212 carbon steel tanks in the vapor space. An investigation of tank materials has been undertaken at SRS to develop a basic understanding of caustic SCC of A285 and A212 grade carbon steels exposed to aqueous solutions, primarily containing sodium hydroxide (NaOH), sodium nitrate (NaNO{sub 3}), and sodium nitrite (NaNO{sub 2}) at temperatures relevant to the operating conditions of both the F and H area plants. This report presents the results of this corrosion testing program. Electrochemical tests were designed using unstressed coupons in a simulated tank environment. The purpose of this testing was to determine the corrosion susceptibility of the tank materials as a function of chemical concentration, pH, and temperature. A285 and A516 (simulates A212 carbon steel) coupons were used to investigate differences in the corrosion of these carbon steels. Electrochemical testing included measurement of the corrosion potential and polarization resistance as well as cyclic potentiodynamic polarization (CPP) testing of coupons. From the CPP experiments, corrosion characteristics were determined including: corrosion potential (E{sub corr}), pitting or breakdown potential (E{sub pit}), and repassivation potential (E{sub prot}). CPP results showed no indications of localized corrosion, such as pitting, and all samples showed the formation of a stable passive layer as evidenced by the positive hysteresis during the scan. Analysis of the CPP data was performed to compare the corrosion susceptibility of the samples under different environmental conditions. Test results indicated that the most important factors affecting corrosion of the steel are the solution temperature, hydroxide concentration, and the material used in constructing the tanks. Variables that did not significantly affect the corrosion susceptibility of the steel were the nitrate or nitrite concentration and the atmosphere in the tank. The passivation current of the coupons increased exponentially with temperature. Longer-term studies of the passivation current are suggested based on results from the literature for iron in highly caustic environments. Polarization resistance studies showed a significant increase in corrosion rate at 125 C and 12 M hydroxide concentration when compared with tests at lower temperatures and lower hydroxide concentrations. Within the temperature and pH range of these tests, iron oxide, Fe{sub 3}O{sub 4}, becomes unstable and could account for the increased corrosion susceptibility. The applicability of these conditions should be confirmed and detailed surface studies should be conducted to determine the corrosion resistance of A285 and A516 carbon steels under these conditions. Surface science studies should also be conducted to determine the role of the carbon steel composition in preventing corrosion under these conditions.
Garcia-Diaz, B.; Roy, A.
Initiation and stable crack growth behavior of API X70 steel at low temperatures (25C [>=] T [>=] [minus]95C)
Small-scale tests employing single edge notch bend (SENB) specimens of API X70 pipeline steel were conducted to assess the initiation and stable growth behavior of this material at test temperatures between 25C and [minus]95C. Material resistance curves were generated based on various proposed J-integral and crack tip opening displacement (CTOD) relationships and criteria for defining crack initiation and stable growth. DC potential drop crack growth monitoring was employed to provide crack propagation data for development of the resistance curves. The temperature dependence of crack initiation and stable growth properties of this material are quantified and presented. Verification of the temperature independence of the normalized J or CTOD tearing modulus is also provided.
Romilly, D.P. (Univ. of British Columbia, Vancouver, B.C. (Canada). Dept. of Mechanical Engineering)
Chaotic iterations versus Spread-spectrum: topological-security and stego-security
A new framework for information hiding security, called topological-security, has been proposed in a previous study. It is based on the evaluation of unpredictability of the scheme, whereas existing notions of security, as stego-security, are more linked to information leaks. It has been proven that spread-spectrum techniques, a well-known stego-secure scheme, are topologically-secure too. In this paper, the links between the two notions of security is deepened and the usability of topological-security is clarified, by presenting a novel data hiding scheme that is twice stego and topological-secure. This last scheme has better scores than spread-spectrum when evaluating qualitative and quantitative topological-security properties. Incidentally, this result shows that the new framework for security tends to improve the ability to compare data hiding scheme.
Guyeux, Christophe; Bahi, Jacques M
Assessment of Pollutant Spread from a Building Basement with three Ventilation Systems
Ventilation aims at providing a sufficient air renewal for ensuring a good indoor air quality (IAQ), yet building energy policies are leading to adapting various ventilation strategies minimising energy losses through air renewal. A recent IAQ evaluation campaign in French dwellings shows important pollution of living spaces by VOCs such as formaldehyde, acetaldehyde or hexanal, particularly in buildings equipped with a garage. Besides, radon emission from soil is a subject of concern in many countries. Several studies are done to understand its release mode and deal with the spread of this carcinogen gas. This paper aims to experimentally assess a contaminant spread from a house basement using mechanical exhaust and balanced ventilation systems, and natural ventilation.
Koffi, Juslin
Astronomical instruments generally possess spatially variant point-spread functions, which determine the amount by which an image pixel is blurred as a function of position. Several techniques have been devised to handle this variability in the context of the standard image deconvolution problem. We have developed an iterative gravitational lens modeling code called Mirage that determines the parameters of pixelated source intensity distributions for a given lens model. We are able to include the effects of spatially variant point-spread functions using the iterative procedures in this lensing code. In this paper, we discuss the methods to include spatially variant blurring effects and test the results of the algorithm in the context of gravitational lens modeling problems.
Rogers, Adam; Fiege, Jason D. [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, R3T-2N2 (Canada)
Exponential Quantum Spreading in a Class of Kicked Rotor Systems near High-Order Resonances
Long-lasting quantum exponential spreading was recently found in a simple but very rich dynamical model, namely, an on-resonance double-kicked rotor model [J. Wang, I. Guarneri, G. Casati, and J. B. Gong, Phys. Rev. Lett. 107, 234104 (2011)]. The underlying mechanism, unrelated to the chaotic motion in the classical limit but resting on quasi-integrable motion in a pseudoclassical limit, is identified for one special case. By presenting a detailed study of the same model, this work offers a framework to explain long-lasting quantum exponential spreading under much more general conditions. In particular, we adopt the so-called "spinor" representation to treat the kicked-rotor dynamics under high-order resonance conditions and then exploit the Born-Oppenheimer approximation to understand the dynamical evolution. It is found that the existence of a flat-band (or an effectively flat-band) is one important feature behind why and how the exponential dynamics emerges. It is also found that a quantitative prediction of the exponential spreading rate based on an interesting and simple pseudoclassical map may be inaccurate. In addition to general interests regarding the question of how exponential behavior in quantum systems may persist for a long time scale, our results should motivate further studies towards a better understanding of high-order resonance behavior in delta-kicked quantum systems.
Hailong Wang; Jiao Wang; Italo Guarneri; Giulio Casati; Jiangbin Gong
How Do You Spread the Word About Saving Energy? | Department of Energy
How Do You Spread the Word About Saving Energy? How Do You Spread the Word About Saving Energy? How Do You Spread the Word About Saving Energy? May 25, 2012 - 2:03pm Addthis Earlier this week, Drew talked about how you can follow Energy Savers and the Office of Energy Efficiency and Renewable Energy on Facebook. But do you share energy saving tips with your own friends, family, and readers? Do you use social media? Do you share tips about how to save energy? And if you do, how? You have the chance to share your thoughts on a question about energy efficiency or renewable energy for consumers. E-mail your responses to the Energy Saver team at firstname.lastname@example.com. Addthis Related Articles Navigating the New EnergySaver.gov What Are Your Top Tips for Saving Energy? By taking simple steps to improve your home's energy efficiency, you can save up to 30 percent on your energy bill. | Infographic by Sarah Gerrity.
Hydrogen permeation and related stress corrosion cracking (SCC) can limit the use of metals and alloys in aqueous environments. The interactions between hydrogen and the
Background Hydrogen permeation and related stress corrosion cracking (SCC) can limit the use in the microstructure initiate the events leading to a crack. Various methods like the post-heat treatment, alloying. These methods however, do not reduce the hydrogen entry below the threshold level that is safe of cracking
Popov, Branko N.
Understanding crack versus cavitation in pressure-sensitive adhesives: the role of kinetics
We perform traction experiments on viscous liquids highly confined between parallel plates, a geometry known as the probe-tack test in the adhesion community. Direct observation during the experiment coupled to force measurement shows the existence of several mechanisms for releasing the stress. Bubble nucleation and instantaneous growth had been observed in a previous work. Upon increasing further the traction velocity or the viscosity, the bubble growth is progressively delayed. At high velocities, cracks at the interface between the plate and the liquid appear before the bubbles have grown to their full size. Bubbles and cracks are thus observed concomitantly. At even higher velocities, cracks develop fully so early that the bubbles are not even visible. We present a theoretical model that describes these regimes, using a Maxwell fluid as a model for the actual fluid, a highly viscous silicon oil. We present the resulting phase diagramme for the different force peak regimes. The predictions are compatible with the data. Our results show that in addition to cavitation, interfacial cracks are encountered in a probe-tack traction test with viscoelastic, \\emph{liquid} materials and not solely with viscoelastic solids like adhesives.
J�r�mie Teisseire; F. Nallet; P. Fabre; Cyprien Gay
Catalytic cracking. (Latest citations from the NTIS Bibliographic database). Published Search
The bibliography contains citations concerning applications of catalytic cracking in fluidized beds, moving beds, refineries, vacuum distillation, and reformers. Design criteria, models, controls, and operating procedures are also discussed. (Contains 250 citations and includes a subject term index and title list.)
Catalytic cracking. (Latest citations from the NTIS data base). Published Search
Catalytic cracking. (Latest citations from the NTIS bibliographic database). Published Search
A New Method To Predict Fatigue Crack Growth Life for the Armored Hull
Based on theories of dynamics of multi-body systems and linear elastic fracture mechanics, by using virtual prototyping technique, the model of tracked vehicle is established, and stress spectrums of the armored hull�s weak points are tested by ... Keywords: Virtual Prototyping, Virtual Test, Fatigue Crack Grow, Simulation
Wang Hongyan; Yang Tao; Shang Qigang
Program on Technology Innovation: Prediction and Evaluation of Environmentally Assisted Cracking in LWR Structural Materials
This report describes the final results of Phase III of a three-year joint research program sponsored by EPRI in collaboration with Fracture & Reliability Research Institute (FRRI) at Tohoku University, Japanese utilities, vendors, and international organizations. The program addressed environmentally assisted cracking (EAC) of light water reactor (LWR) structural materials in pressurized water reactor (PWR) and boiling water reactor (BWR) environments.
tensor 0 yield stress () Taylor's resolved shear stress AISI American Iron and Steel Institute CTOD Crack in this paper are typical for the AISI 316L austenitic stainless steel, which is extensively used in nuclear industry (e.g. pipes) and has also been selected for a number of components of the International
Investigation of Potential Concrete Tie Rail Seat Deterioration Mechanisms: Cavitation Erosion and Hydraulic Pressure Cracking
Investigation of Potential Concrete Tie Rail Seat Deterioration Mechanisms: Cavitation Erosion and Hydraulic Pressure Cracking 10-2411 Transportation Research Board 89th Annual Meeting Submitted: November 15-2411 1 ABSTRACT Rail seat deterioration (RSD) is the most critical problem with concrete tie performance
Barkan, Christopher P.L.
This report describes the interim results of PEACE-E, a Five-year extension of the joint research program sponsored by EPRI in collaboration with the Fracture Reliability Research Institute (FRRI) at Tohoku University, Japanese utilities, vendors, and international organizations. The program addressed environmentally assisted cracking (EAC) of light water reactor structural materials in PWR and BWR environments.
Stress corrosion cracking behavior of Alloy 600 in high temperature water
SCC susceptibility of Alloy 600 in deaerated water at 360 C (statically loaded U-bend specimens) is dependent on microstructure and whether the material was cold-worked and annealed (CWA) or hot-worked and annealed (HWA). All cracking was intergranular, and materials lacking grain boundary carbides were most susceptible to SCC initiation. CWA tubing materials are more susceptible to SCC initiation than HWA ring-rolled forging materials with similar microstructures (optical metallography). In CWA tubing materials, one crack dominated and grew to a visible size. HWA materials with a low hot-working finishing temperature (980 C) and a high-temperature final anneal (>1040 C), with grain boundaries that are fully decorated, developed only microcracks in all specimens. These materials did not develop large, visually detectable cracks, even after more than 300 weeks exposure. A low-temperature thermal treatment (610 C for 7h), which reduces or eliminates SCC in Alloy 600, did not eliminate microcrack formation in high temperature processed HWA materials. Conventional metallographic and analytical electron microscopy (AEM) were done on selected materials to identify the factors responsible for the observed differences in cracking behavior. Major difference between high-temperature HWA and low-temperature HWA and CWA materials was that the high temperature processing and final annealing produced predominantly ``semi-continuous`` dendritic M{sub 7}C{sub 3} carbides along grain boundaries with a minimal amount of intragranular carbides. Lower temperature processing produced intragranular M7C3 carbides, with less intergranular carbides.
Webb, G.L.; Burke, M.G.
Modeling the cracking process of rocks from continuity to discontinuity using a cellular automaton
A rock discontinuous cellular automaton (RDCA) was developed for modeling rock fracturing processes from continuous to discontinuous deformation under mechanical loading. RDCA is an integration of the following basic concepts: (1) representation of heterogeneity ... Keywords: Cracking process, Discontinuity, Elasto-plastic cellular automaton, Level set, Partition of unity, Rock discontinuous cellular automaton
Peng-Zhi Pan; Fei Yan; Xia-Ting Feng
Effect of Blast Design on Crack Response C.H. Dowding
to determine those with the best correlation. Variations in the ground motion and air pressure wave (air blast Conference Siebert and Dowding (2000) described development of the autonomous crack measurement (ACM) system). These theses are available online at www.iti.northwestern.edu/research/current/acm. This article describes
Technical note: Filling trim cracks on GPU-rendered solid models
We present an algorithm for improving the rendering appearance of CAD models with trimmed freeform surfaces when evaluated on graphics processing units (GPUs). Rendering on client GPUs allows mechanical CAD to embrace cloud computing by storing a single ... Keywords: Cracks, GPU rendering, Geometric modeling, Trimmed surfaces
Sushrut Pavanaskar; Sara Mcmains
Crack growth behavior of encapsulation processed SiC-PMMA particulate composites
The effect of processing on the fatigue crack propagation and fracture toughness of ceramic-polymer composites was investigated. A new process for composite production was developed with homogeneous particle distribution and low residual stress levels in mind. PMMA was uniformly distributed by encapsulating the SiC substrate by means of precipitation polymerization. The encapsulation processed powders were then compacted at temperatures above T{sub g} to form the composite. The encapsulation process was optimized by varying the initial concentrations of the reactants until homogeneous nucleation was suppressed. The coatings were found to be continuous at the SiC-PMMA interface, with particle agglomeration occurring between coated particles. Polymer loadings equivalent to 30 vol % SiC were achieved. Composites of several particle size ranges were tested under cyclic fatigue and static loading conditions. Fatigue growth rates and fracture toughness data display a trend of increasing crack growth resistance with increasing particle size, with encapsulation processed composites outperforming conventionally cast composites in both cyclic fatigue and fracture resistance. The largest K{sub Ic} value was found to be 2.95 MPa(m){sup 1/2}, a factor of 3 increase over un-reinforced PMMA. The roles of crack deflection, shielding, bridging, and pinning in enhancing toughness were discussed in light of crack profile fracture surface details. 65 refs., 30 figs., 2 tabs.
Sheu, C.H.
This report describes the interim results of Phase III of a joint research program sponsored by EPRI in collaboration with the Fracture Reliability Research Institute (FRRI) at Tohoku University, Japanese utilities, vendors, and international organizations to address environmentally assisted cracking (EAC) of LWR structural materials.
Overlapping double etch technique for evaluation of metallic alloys to stress corrosion cracking
A double overlapping etch zone technique for evaluation of the resistance of metallic alloys to stress corrosion cracking. The technique involves evaluating the metallic alloy along the line of demarcation between an overlapping double etch zone and single etch zone formed on the metallic alloy surface.
Steeves, Arthur F. (Schenectady, NY); Stewart, James C. (Loudonville, NY)
A double overlapping etch zone technique for evaluation of the resistance of metallic alloys to stress corrosion cracking is described. The technique involves evaluating the metallic alloy along the line of demarcation between an overlapping double etch zone and single etch zone formed on the metallic alloy surface.
Dispersion of elastic moduli in a porous-cracked rock: Theoretical predictions for squirt-flow
. Attenuation and dispersion of compressional waves in fluid-filled porous rocks with partial gas saturationDispersion of elastic moduli in a porous-cracked rock: Theoretical predictions for squirt-flow M Available online xxxx Keywords: Frequency dispersion Rock properties Bimodal porosity Effective medium
A Parametric Study of the Lead-Induced Stress Corrosion Cracking of Alloy 690
Alloy 690 steam generator tubing, which has been the material of choice for replacement steam generators, is susceptible to lead-induced stress corrosion cracking (PbSCC) in alkaline environments. No obvious correlation was found between processing parameters or material characteristics and PbSCC susceptibility.
Influence of microstructure on stress corrosion cracking of mild steel in synthetic caustic-nitrate nuclear waste solution
The influence of alloy microstructure on stress corrosion cracking of mild steel in caustic-nitrate synthetic nuclear waste solutions was studied. An evaluation was made of the effect of heat treatment on a representative material (ASTM A 516 Grade 70) used in the construction of high activity radioactive waste storage tanks at Savannah River Plant. Several different microstructures were tested for susceptibility to stress corrosion cracking. Precracked fracture specimens loaded in either constant load or constant crack opening displacement were exposed to a variety of caustic-nitrate and nitrate solutions. Results were correlated with the mechanical and corrosion properties of the microstructures. Crack velocity and crack arrest stress intensity were found to be related to the yield strength of the steel microstructures. Fractographic evidence indicated pH depletion and corrosive crack tip chemistry conditions even in highly caustic solutions. Experimental results were compatible with crack growth by a strain- assisted anodic dissolution mechanism; however, hydrogen embrittlement also was considered possible. (auth)
Sarafian, P.G.
An investigation of penetrant techniques for detection of machining-induced surface-breaking cracks on monolithic ceramics
The purpose of this effort was to evaluate penetrant methods for their ability to detect surface-breaking cracks in monolithic ceramic materials with an emphasis on detection of cracks generated by machining. There are two basic penetrant types, visible and fluorescent. The visible penetrant method is usually augmented by powder developers and cracks detected can be seen in visible light. Cracks detected by fluorescent penetrant are visible only under ultraviolet light used with or without a developer. The developer is basically a powder that wicks up penetrant from a crack to make it more observable. Although fluorescent penetrants were recommended in the literature survey conducted early in this effort, visible penetrants and two non-standard techniques, a capillary gaseous diffusion method under development at the institute of Chemical Physics in Moscow, and the {open_quotes}statiflux{close_quotes} method which involves use of electrically charged particles, were also investigated. SiAlON ring specimens (1 in. diameter, 3/4 in. wide) which had been subjected to different thermal-shock cycles were used for these tests. The capillary gaseous diffusion method is based on ammonia; the detector is a specially impregnated paper much like litmus paper. As expected, visible dye penetrants offered no detection sensitivity for tight, surface-breaking cracks in ceramics. Although the non-standard statiflux method showed promise on high-crack-density specimens, it was ineffective on limited-crack-density specimens. The fluorescent penetrant method was superior for surface-breaking crack detection, but successful application of this procedure depends greatly on the skill of the user. Two presently available high-sensitivity fluorescent penetrants were then evaluated for detection of microcracks on Si{sub 3}N{sub 4} and SiC from different suppliers. Although 50X optical magnification may be sufficient for many applications, 200X magnification provides excellent delectability.
Forster, G.A.; Ellingson, W.A.
In-Line Crack and Stress Detection in Silicon Solar Cells Using Resonance Ultrasonic Vibrations
Statement of Problem and Objectives. Wafer breakage in automated solar cell production lines is identified as a major technical problem and a barrier for further cost reduction of silicon solar module manufacturing. To the best of our knowledge, there are no commercial systems addressing critical needs for in-line inspection of the mechanical quality of solar wafers and cells. The principal objective of the SBIR program is to validate through experiments and computer modeling the applicability of the Resonance Ultrasonic Vibrations system, which ultimately can be used as a real-time in-line manufacturing quality control tool for fast detection of mechanically unstable silicon solar cells caused by cracks. The specific objective of Phase II is to move the technology of in-line crack detection from the laboratory level to commercial demonstration through development of a system prototype. The fragility of silicon wafers possessing low mechanical strength is attributed to peripheral and bulk millimeter-length cracks. The research program is based on feasibility results obtained during Phase I, which established that: (i) the Resonance Ultrasonic Vibrations method is applicable to as-cut, processed wafers and finished cells; (ii) the method sensitivity depends on the specific processing step; it is highest in as-cut wafers and lowest in wafers with metallization pattern and grid contacts; (iii) the system is capable of matching the 2.0 seconds per wafer throughput rate of state-of-art solar cell production lines; (iv) finite element modeling provides vibration mode analysis along with peak shift versus crack length and crack location dependence; (v) a high 91% crack rejection rate was confirmed through experimentation and statistical analysis. The Phase II project has the following specific tasks: (i) specify optimal configurations of the in-line system�?¢�?�?�?�?s component hardware and software; (ii) develop and justify a system prototype that meets major specifications for an in-line crack detection unit, such as high throughput rate, high level of stability, reproducibility of data acquisition and analysis, and high sensitivity with respect to crack length and crack location; (iii) design a system platform that allows easy integration within and adaptation to various solar cell belt-type production lines; (iv) develop a testing protocol providing quality certification of the production-grade system. Commercial Application of the proposed activity consists of bringing to the solar market a new high-tech product based on an innovative solution and patented methodology to contribute to cost reduction of silicon solar module production. The solar industry, with crystalline silicon as a dominant segment, shows outstanding performance, with approximately 25% yearly growth during the last years. Despite a slowdown with only 5.6 GW installations in 2009, solar module production for the 2010 and 2011 years was recovered. According to European Photonics Industry Consortium new solar PV installations grow by 56% compared to 2010 reached 64.7 GW in 2011. Revenues in the PV industry reached a record high of $93 billion in 2011, a 13.4 percent gain over 2010 â�?�? and 150 percent over 2009. This growth was forecasted to continue in 2013 with double digits growth. The solar industry is economically driven to make solar panels of the highest conversion efficiency and reliability at the lowest production cost. The Resonance Ultrasonic Vibration system addresses critical needs of the silicon-based solar industry by providing a quality control method and tool, which will improve productivity, increase reliability of products and reduce manufacturing cost of solar panels.
Ostapenko, Sergei
Experimental and seismological constraints on the rheology, evolution, and alteration of the lithosphere at oceanic spreading centers
Oceanic spreading centers are sites of magmatic, tectonic, and hydrothermal processes. In this thesis I present experimental and seismological constraints on the evolution of these complex regions of focused crustal accretion ...
DeMartin, Brian J., 1976-
A Basinwide Estimate of Vertical Mixing in the Upper Pycnocline: Spreading of Bomb Tritium in the North Pacific Ocean
The vertical diffusivity KV in the upper half-kilometer of the North Pacific subtropical pycnocline is estimated from observations of the spreading rate of anthropogenic tritium. The calculation is based on approximately 300 ocean tritium ...
Dan E. Kelley; Kim A. Van Scoy
Agricultural pathogen decontamination technology-reducing the threat of infectious agent spread.
Outbreaks of infectious agricultural diseases, whether natural occurring or introduced intentionally, could have catastrophic impacts on the U.S. economy. Examples of such agricultural pathogens include foot and mouth disease (FMD), avian influenza (AI), citrus canker, wheat and soy rust, etc. Current approaches to mitigate the spread of agricultural pathogens include quarantine, development of vaccines for animal diseases, and development of pathogen resistant crop strains in the case of plant diseases. None of these approaches is rapid, and none address the potential persistence of the pathogen in the environment, which could lead to further spread of the agent and damage after quarantine is lifted. Pathogen spread in agricultural environments commonly occurs via transfer on agricultural equipment (transportation trailers, tractors, trucks, combines, etc.), having components made from a broad range of materials (galvanized and painted steel, rubber tires, glass and Plexiglas shields, etc), and under conditions of heavy organic load (mud, soil, feces, litter, etc). A key element of stemming the spread of an outbreak is to ensure complete inactivation of the pathogens in the agricultural environment and on the equipment used in those environments. Through the combination of enhanced agricultural pathogen decontamination chemistry and a validated inactivation verification methodology, important technologies for incorporation as components of a robust response capability will be enabled. Because of the potentially devastating economic impact that could result from the spread of infectious agricultural diseases, the proposed capability components will promote critical infrastructure protection and greater border and food supply security. We investigated and developed agricultural pathogen decontamination technologies to reduce the threat of infectious-agent spread, and thus enhance agricultural biosecurity. Specifically, enhanced detergency versions of the patented Sandia decontamination chemistry were developed and tested against a few surrogate pathogens under conditions of relatively heavy organic load. Tests were conducted on surfaces commonly found in agricultural environments. Wide spectrum decontamination efficacy, low corrosivity, and biodegradability issues were addressed in developing an enhanced detergency formulation. A method for rapid assessment of loss of pathogenic activity (inactivation) was also assessed. This enhanced technology will enable rapid assessment of contamination following an intentional event, and will also be extremely useful in routine assessment of agricultural environments. The primary effort during the second year was progress towards a demonstration of both decontamination and viral inactivation technologies of Foot and Mouth virus (FMDv) using the modified SNL chemistry developed through this project. Lab studies using a surrogate virus (bovine enterovirus) were conducted using DF200, modified DF200 chemistry, and decontaminants currently recommended for use in heavily loaded organic, agricultural environments (VirkonS, 10% bleach, sodium hydroxide and citric acid). Tests using actual FMD virus will be performed at the Department of Homeland Security's Plum Island facilities in the fall of 2005. Success and the insight gained from this project will lead to enhanced response capability, which will benefit agencies such as USDA, DHS, DOD, and the agricultural industry.
Betty, Rita G.; Bieker, Jill Marie; Tucker, Mark David
How to measure the spreading width for decay of superdeformed nuclei
A new expression for the branching ratio for the decay via the E1 process in the normal-deformed band of superdeformed nuclei is given within a simple two-level model. Using this expression, the spreading or tunneling width Gamma^downarrow for superdeformed decay can be expressed entirely in terms of experimentally known quantities. We show how to determine the tunneling matrix element V from the measured value of Gamma^downarrow and a statistical model of the energy levels. The accuracy of the two-level approximation is verified by considering the effects of the other normal-deformed states.
D. M. Cardamone; C. A. Stafford; B. R. Barrett
A Hybrid Sensitivity Analysis Approach for Agent-based Disease Spread Models
Agent-based models (ABM) have been widely deployed in different fields for studying the collective behavior of large numbers of interacting agents. Of particular interest lately is the application of agent-based and hybrid models to epidemiology, specifically Agent-based Disease Spread Models (ABDSM). Validation (one aspect of the means to achieve dependability) of ABDSM simulation models is extremely important. It ensures that the right model has been built and lends confidence to the use of that model to inform critical decisions. In this report, we describe our preliminary efforts in ABDSM validation by using hybrid model fusion technology.
Pullum, Laura L [ORNL; Cui, Xiaohui [New York Institute of Technology (NYIT)
Prediction of early-age cracking of UHPC materials and structures : a thremo-chemo-mechanics approach
Ultra-High Performance Concrete [UHPC] has remarkable performance in mechanical properties, ductility, economical benefit, etc., but early-age cracking of UHPC can become an issue during the manufacturing process due to ...
Shim, JongMin, 1975-
Research Article HZSM-5 Catalyst for Cracking Palm Oil to Gasoline: A Comparative Study with and without Impregnation
It is important to develop a renewable source of energy to overcome a limited source fossil energy. Palm oil is a potential alternative and environmental friendly energy resource in Indonesia due to high production capacity of this vegetable oil. The research studied effect of catalyst to selectivity of biofuel product from cracking of palm oil. The catalyst consisted of HZSM-5 catalyst with or without impregnation. The research was conducted in two steps, namely catalyst synthesized and catalytic cracking process. HZSM-5 was synthesized using Plank methods. The characterization of the synthesized catalysts used AAS (Atomic Absorption Spectroscopy) and BET (Brunaueur Emmet Teller). The cracking was carried out in a fixed bed microreactor with diameter of 1 cm and length of 16 cm which was filled with 0.6 gram catalyst. The Ni/HZSM-5 catalyst was recommended for cracking palm oil for the high selectivity to gasoline. � 2013
Achmad Roesyadi; Danawati Hariprajitno; N. Nurjannah; Santi Dyah Savitri
Crustal Rock Fracture Mechanics for Design and Control of Artificial Subsurface Cracks in Geothermal Energy Extraction Engineering ({Gamma}-Project)
Recently a significant role of artificial and/or natural cracks in the geothermal reservoir has been demonstrated in the literatures (Abe, H., et al., 1983, Nielson, D.L. and Hullen, J.B., 1983), where the cracks behave as fluid paths and/or heat exchanging surfaces. Until now, however, there are several problems such as a design procedure of hydraulic fracturing, and a quantitative estimate of fluid and heat transfer for reservoir design. In order to develop a design methodology of geothermal reservoir cracks, a special distinguished research project, named as ''{Lambda}-Project'', started at Tohoku University (5 years project, 1983-1988). In this project a basic fracture mechanics model of geothermal reservoir cracks is being demonstrated and its validation is being discussed both theoretically and experimentally. This paper descibes an outline of ''{Lambda}-Project''.
Abe, Hiroyuki; Takahashi, Hideaki
Mechanics and Mechanisms of Environmentally Assisted Cracking of Alloys 132/182 in BWR and PWR Environments
This report documents research on the mechanics and mechanisms of environmentally assisted cracking of Alloys 132/182 in boiling water reactor (BWR) and pressurized water reactor (PWR) environments.
Aluminum nitride transitional layer for reducing dislocation density and cracking of AlGaN epitaxial films
A denticulated Group III nitride structure that is useful for growing Al.sub.xGa.sub.1-xN to greater thicknesses without cracking and with a greatly reduced threading dislocation (TD) density.
Allerman, Andrew A.; Crawford, Mary H.; Lee, Stephen R.
Effect of aging on the fatigue crack growth kinetics of an Al-Zn-Mg-Cu alloy in two directions
There have been investigations discussing the effect of aging condition, and thereby the microstructure, on the fatigue crack growth characteristics of precipitation hardening alloys. Lindigkeit et al.., testing an Al-Zn-Mg-Cu alloy of composition corresponding to the commercial alloy 7075 concluded that the crack propagation resistance of underaged microstructures with shearable precipitates is significantly higher than overaged samples of same strength containing non-shearable particles. They reported that this behavior cannot be explained on the basis of slip reversibility alone. A similar conclusion is drawn by Zaiken and Ritchie from investigations on the effect of microstructure on the fatigue crack growth rate of an 7150 aluminum alloy, which is a somewhat high-purity version of the alloy 7050, with lower Fe and Si contents. It is also interesting that aging conditions showing high resistance to fatigue crack growth at low [Delta]K regimes, do not necessarily retain their superiority at medium and high stress intensity ranges.
Alpay, S.P.; Guerbuez, R. (Middle East Technical Univ., Ankara (Turkey). Dept. of Metallurgical Engineering)
A soft computing approach to crack detection and impact source identification with field-programmable gate array implementation
The real-time nondestructive testing (NDT) for crack detection and impact source identification (CDISI) has attracted the researchers fromdiverse areas. This is apparent fromthe current work in the literature. CDISI has usually been performed by visual ...
Arati M. Dixit, Harpreet Singh
Influence of the material substructure on crack propagation: a unified treatment
The influence of the material texture (substructure) on the force driving the crack tip in complex materials admitting Ginzburg-Landau-like energies is analyzed in a three-dimensional continuum setting. The theory proposed accounts for finite deformations and general coarse-grained order parameters. A modified expression of the J-integral is obtained together with other path-integrals which are necessary to treat cases where the process zone around the tip has finite size. The results can be applied to a wide class of material substructures. As examples, cracks in ferroelectrics and in materials with strain-gradient effects are discussed: in these cases the specializations of the general results fit reasonably experimental data.
Paolo Maria Mariano
A preliminary investigation of the effects of environmentally assisted cracking on natural gas transmission pipelines
Concepts for the development of a model to predict natural gas transmission pipeline lifetime in a corrosive environment are constructed. Primarily, the effects of environmentally assisted cracking (EAC) are explored. Tensile test specimens from a sample of API 5L X-52 pipeline were tested in a simulated groundwater solution and subsequently analyzed. The results suggested that the simulated environment ultimately reduced the ductility of the test specimens; however, no evidence of ??classical?? stress corrosion crack morphology was discovered. However, corrosion pits up to 0.75 mm (0.03 in) were revealed during metallographic analysis. A Marin factor analogy and an energy method concept are suggested and explored. Ultimately, the test data set was too small for the results to be of any directly applicable significance.
Curbo, Jason Wayne
Grain-boundary cavitation and weld-underbead cracking in DOP-26 iridium alloy
Plutonium-238 oxide fuel pellets for the General Purpose Heat Source Radioisotopic thermoelectric generators to be used on the NASA Galileo Mission to Jupiter and the International Solar Polar Mission are produced and encapsulated in DOP-26 iridium alloy at the Savannah River Plant. DOP-26 iridium alloy was developed at the Oak Ridge National Laboratory and contains nominally 0.3 weight-percent tungsten, 60-ppM thorium and 50-ppM aluminum. Underbead cracks occasionally occur in the girth weld on the iridium alloy cladding in the area where the gas tungsten arc is quenched. A variety of electron beam techniques have been used to determine the cause of cracking. Results are discussed. (WHK)
Mosley, W.C. Jr.
Catalytic cracking of aromatic hydrocarbons. Final report, October 1984-March 1986
Iron containing minerals and chars were screened as cracking catalysts for aromatic hydrocarbons (AHC) in simulated gasifier effluents. Catalytic activities of six minerals and two chars were measured and used to infer fundamental hetereogeneous rate constants using measured properties of the pore structure of the solids. Measurements were made for 200 ppM and 2000 ppM benzene cracking over the temperature range 400 to 1000/sup 0/C. The active catalyst under gasifier conditions was found to be FeO. The minerals have a higher reactivity per unit mass in chars than in a pure form. H/sub 2/S was found to reduce the catalytic activity to one third of the unpoisoned value, but the catalysts maintained this reduced activity. These minerals have the potential to be economically feasible, disposable catalysts in a fixed bed or fluidized bed process if they can survive for ten hours. 8 refs., 33 figs., 3 tabs.
Simons, G.A.; Ham, D.O.; Moniz, G.A.
Elastic and plastic strains and the stress corrosion cracking of austenitic stainless steels. Final report
The influence of elastic (stress) and plastic (cold work) strains on the stress corrosion cracking of a transformable austenitic stainless steel was studied in several aqueous chloride environments. Initial polarization behavior was active for all deformation conditions as well as for the annealed state. Visual observation, potential-time, and current-time curves indicated the development of a pseudo-passive (flawed) film leading to localized corrosion, occluded cells and SCC. SCC did not initiate during active corrosion regardless of the state of strain unless severe low temperature deformation produced a high percentage of martensite. Both elastic and plastic deformation increased the sensitivity to SCC when examined on the basis of percent yield strength. The corrosion potential, the critical cracking potential, and the potential at which the current changes from anodic to cathodic were essentially unaffected by deformation. It is apparent that the basic electrochemical parameters are independent of the bulk properties of the alloy and totally controlled by surface phenomena.
Vaccaro, F.P.; Hehemann, R.F.; Troiano, A.R.
Thermonuclear Flame Spreading on Rapidly Spinning Neutron Stars: Indications of the Coriolis Force?
Millisecond period brightness oscillations during the intensity rise of thermonuclear X-ray bursts are likely caused by an azimuthally asymmetric, expanding burning region on the stellar surface. The time evolution of the oscillation amplitude during the intensity rise encodes information on how the thermonuclear flames spread across the stellar surface. This process depends on properties of the accreted burning layer, surface fluid motions, and the surface magnetic field structure, and thus can provide insight into these stellar properties. We present two examples of bursts from different sources that show a decrease in oscillation amplitude during the intensity rise. Using theoretical modeling, we demonstrate that the observed amplitude evolution of these bursts is not well described by a uniformly expanding circular burning region. We further show that by including in our model the salient aspects of the Coriolis force (as described by Spitkovsky, Levin, and Ushomirsky) we can qualitatively reproduce the observed evolution curves. Our modeling shows that the evolutionary structure of burst oscillation amplitude is sensitive to the nature of flame spreading, while the actual amplitude values can be very useful to constrain some source parameters.
Sudip Bhattacharyya; Tod E. Strohmayer
Effects of Marine Environments on Stress Corrosion Cracking of Austenitic Stainless Steels
It has been clearly demonstrated in laboratory and field studies plus field experience with actual and simulated components that the stress corrosion cracking (SCC) of austenitic stainless steel can occur at ambient temperatures in marine-type environments. Therefore, the SCC concerns for spent fuel storage canisters identified in a November 2004 presentation by Nuclear and Industrial Safety Agency (NISA) and Central Research Institute of Electric Power Industry (CRIEPI) representatives are clearly warra...
Physical significance of the curvature varifold-based description of crack nucleation
The nucleation and/or growth of cracks in elastic-brittle solids has been recently described in [14] in terms of a special class of measures and with a variational technique requiring the minimization of a certain energy over classes of bodies. Here, the physical foundations of the theory and the basic ideas leading to it are described and commented further on. A view on certain possible developments and shifts toward different settings is also given. This article has expository character.
Composite tube cracking in kraft recovery boilers: A state-of-the-art review
Beginning in the mid-1960s, increasing energy costs in Finland and Sweden made energy recovery more critical to the cost-effective operation of a kraft pulp mill. Boiler designers responded to this need by raising the steam operating pressure, but almost immediately the wall tubes in these new boilers began to corrode rapidly. Test panels installed in the walls of the most severely corroding boiler identified austenitic stainless steel as sufficiently resistant to the new corrosive conditions, and discussions with Sandvik AB, a Swedish tube manufacturer, led to the suggestion that coextruded tubes be used for water wall service in kraft recovery boilers. Replacement of carbon steel by coextruded tubes has solved most of the corrosion problems experienced by carbon steel wall tubes, however, these tubes have not been problem-free. Beginning in early 1995, a multidisciplinary research program funded by the US Department of Energy was established to investigate the cause of cracking in coextruded tubes and to develop improved materials for use in water walls and floors of kraft recovery boilers. One portion of that program, a state-of-the-art review of public- and private-domain documents related to coextruded tube cracking in kraft recovery boilers is reported here. Sources of information that were consulted for this review include the following: tube manufacturers, boiler manufacturers, public-domain literature, companies operating kraft recovery boilers, consultants and failure analysis laboratories, and failure analyses conducted specifically for this project. Much of the information contained in this report involves cracking problems experienced in recovery boiler floors and those aspects of spout and air-port-opening cracking not readily attributable to thermal fatigue. 61 refs.
Singbeil, D.L.; Prescott, R. [Pulp and Paper Research Inst. of Canada, Vancouver, British Columbia (Canada); Keiser, J.R.; Swindeman, R.W. [Oak Ridge National Lab., TN (United States)
Experimental and analytical assessment of circumferential through-wall cracked pipes under pure bending
This study was performed to assess the validity of various techniques to predict crack initiation loads and maximum loads for circumferentially through-wall-cracked pipes under pure bending. Experimental data were developed for both carbon steel and stainless steel pipes. Predictions of crack initiation and maximum loads were made using the net-section-collapse method, three different J-estimation schemes, and the British R6 method. The net-section-collapse method gave good maximum-load predictions for certain types of pipe; however, for large diameter and/or low toughness pipe this analysis method tended to overpredict the experimental maximum load. A plastic-zone screening criterion was developed to show when this method was valid and when elastic-plastic fracture mechanics should be used. In the J-estimation scheme analyses, sensitivity studies were conducted to assess the fit of the Ramberg-Osgood coefficients, as well as the use of deformation J and modified J (J/sub M/) crack growth resistance curves. The results showed that the GE/EPRI estimation scheme underpredicted the experimental loads by the greatest amount. The LBB.NRC and Paris methods gave more accurate predictions. The GE/EPRI method was also found to be more sensitive to the fit of the stress-strain curve than the LBB.NRC method. The R6 method underpredicted the failure loads for all cases. For maximum load predictions, the GE/EPRI method still underpredicted the experimental load when the J/sub M/ resistance curve was used. The other methods occasionally overpredicted the maximum load using J/sub M/-resistance curve.
Scott, P.; Brust, F.
This report describes the interim results of PEACE-E, a five-year extension of the joint research program sponsored by EPRI in collaboration with Fracture & Reliability Research Institute (FRRI) at Tohoku University, Japanese utilities, vendors, and international organizations. The program addressed environmentally assisted cracking (EAC) of light water reactor (LWR) structural materials in pressurized water reactor (PWR) and boiling water reactor (BWR) environments.
Steam Generator Management Program: Onset of Fatigue Cracking in Steam Generator Tubes With Through Wall Flaws
Leak rate tests of steam generator tubing with stress corrosion cracks and electrodischarge machining notches were conducted at Argonne National Laboratory (ANL) under the sponsorship of the U.S. Nuclear Regulatory Commission. Some test specimens displayed a significant leak rate increase under constant pressure hold. It was suspected that fatigue caused by jet�structure interaction was responsible for the increased leak rate. EPRI Reports 1015123 and 1016560 investigated the ANL test results in terms of...
Final Review of the Cooperative Irradiation-Assisted Stress Corrosion Cracking Research Program
Irradiation-assisted stress corrosion cracking (IASCC) has affected reactor core internal structures fabricated from austenitic stainless steels in both pressurized water reactors (PWRs) and boiling water reactors (BWRs). This report presents the final review of work sponsored by the Cooperative IASCC Research (CIR) program. The CIR program is an international research effort designed to address IASCC in light water reactor (LWR) components. The program's goal is to develop a mechanistically based predic...
Fracture toughness and crack-resistance curve behavior in metallic glass-matrix composites
Nonlinear-elastic fracture mechanics methods are used to assess the fracture toughness of bulk metallic glass (BMG) composites; results are compared with similar measurements for other monolithic and composite BMG alloys. Mechanistically, plastic shielding gives rise to characteristic resistance?curve behavior where the fracture resistance increases with crack extension. Specifically, confinement of damage by second?phase dendrites is shown to result in enhancement of the toughness by nearly an order of magnitude relative to unreinforced glass.
Launey, Maximilien E.; Hofmann, Douglas C.; Suh, Jin-Yo; Kozachkov, Henry; Johnson, William L.; Ritchie, Robert O.
The Role of Moisture and Hydrogen in Hot-Salt Cracking of Titanium Alloys
This study investigated the role of moisture and hydrogen in the stress corrosion cracking of Ti-8Al-1Mo-1V exposed to hot chloride salts. The adsorption and retention of moisture during the application of salt deposits and subsequent heating, and the extent of HCl and hydrogen generation during corrosion were studied using radiotracer techniques and mass spectrographic analysis of volatile corrosion products.
Rideout, S.P.
Steam Generator Management Program: Assessment of Channel Head Susceptibility to Primary Water Stress Corrosion Cracking
There have been several documented cases of primary water stress corrosion cracking (PWSCC) indications in the divider plate assembly in Westinghouse model steam generators in operation outside the United States. These indications were observed in plants that operated with proper primary water chemistry. The function of the divider plate in most steam generators is to separate the cold and hot legs of the channel head as the primary water enters the steam generator so that the primary coolant flows up in...
Steam Generator Management Program: Conditions Causing Lead Stress Corrosion Cracking of Steam Generator Tubing, Alloy 690TT
Tube damage by intergranular attack/stress corrosion cracking (IGA/SCC) continues to result in steam generator tubing degradation, plugging of tubes, and eventual replacement of steam generators. �The present strategy for mitigating IGA/SCC is based on the assumption that crack initiation and propagation rates depend on the at-temperature pH (pHT), the electrochemical potential, and the development of crevice areas.� Accordingly, all plants have adopted the practice of ...
Materials Reliability Program: Technical Basis for Primary Water Stress Corrosion Cracking Mitigation by Surface Stress Improvement (MRP-267, Revision 1)
During the past two decades, stress corrosion cracking (SCC) has become the most relevant phenomenon affecting nuclear plant availability and plant lifetime management. SCC can lead to increased costs for operation, maintenance, assessment, repair, and replacement of boiling water reactor (BWR) and pressurized water reactor (PWR) components. Alloy 600 and 82/182 materials, which are widely used in PWR systems, are susceptible to primary water stress corrosion cracking (PWSCC). PWSCC has been reported in ...
BWRVIP-265: BWR Vessel and Internals Project, Crack Growth in High Fluence BWR Materials-Phase 2
The Boiling Water Reactor Vessel and Internals Project (BWRVIP) has developed a methodology to evaluate crack growth rates (CGR) in irradiated stainless steel components in the BWR vessel. This methodology is documented in BWRVIP-99-A: BWR Vessel and Internals Project, Crack Growth Rates in Irradiated Stainless Steels in BWR Internal Components (EPRI report 1016566), and is applicable to neutron doses of 0.7 to 4.2 displacements per atom (dpa) (5x1020 to 3x1021 ...
Strain Response of Hot-Mix Asphalt Overlays for Bottom-Up Reflective Cracking
This paper examines the strain response of typical HMA overlays above jointed PCC slabs prone to bottom-up reflective cracking. The occurrence of reflective cracking under the combined effect of traffic and environmental loading significantly reduces the design life of the HMA overlays and can lead to its premature failure. In this context, viscoelastic material properties combined with cyclic vehicle loadings and pavement temperature distribution were implemented in a series of FE models in order to study the evolution of horizontal tensile and shear strains at the bottom of the HMA overlay. The effect of several design parameters, such as subbase and subgrade moduli, vehicle speed, overlay thickness, and temperature condition, on the horizontal and shear strain response was investigated. Results obtained show that the rate of horizontal and shear strain increase at the bottom of the HMA overlay drop with higher vehicle speed, higher subgrade modulus, and higher subbase modulus. Moreover, the rate of horizontal strain accumulation increases with higher overlay thickness. Although initial strain values were higher at positive pavement temperature distributions, the corresponding rate of strain increase were higher at negative pavement temperatures. Finally, an extrapolation of the strain history curve for various pavement design parameters was used to estimate the number of cycles for bottom-up crack initiation.
Ziad G. Ghauch; Grace G. Abou Jaoude
Hydrogen induced surface cracking in an 8090 Al-Li alloy during high cycle fatigue
In recent years, there has been an increasing interest in understanding the effects of aggressive or moist environments on the properties of Al-Li alloys. However, most of the existing work has been focused on their stress corrosion cracking resistance. Consequently, only a few reports are available on the environmental fatigue strength of these alloys. Upon exposure to aggressive environments, the fatigue crack propagation resistance can be detrimentally affected. R. Piascik and R. Gangloff found enhanced cyclic crack growth rates in an Al-Li-Cu alloy when a critical water vapor pressure was exceeded. Thermodynamically, at atmospheric pressures, strong interactions between hydrogen and lithium are expected to give rise to stable lithium hydrides. Evidence for the development of hydride phases in Al-Li alloys exposed to hydrogen environments has been reported by various workers. Thus, it is likely that HE via hydride formation can be the relevant mechanisms in Al-Li alloys that have been in contact with hydrogen. Since lithium hydrides are stable up to temperatures of 773 K, previous hydrogen exposure can lead to an irreversible mode of embrittlement. Thus, it was the objective of the present work to investigate the effects of hydrogen during aging on the ensuing high cycle fatigue (HCF) performance of an 8090 Al-Li alloy.
Laffin, C.; Raghunath, C.R.; Lopez, H.F. (Univ. of Wisconsin, Milwaukee, WI (United States). Materials Dept.)
Crack growth rates of irradiated austenitic stainless steel weld heat affected zone in BWR environments.
Austenitic stainless steels (SSs) are used extensively as structural alloys in the internal components of reactor pressure vessels because of their superior fracture toughness. However, exposure to high levels of neutron irradiation for extended periods can exacerbate the corrosion fatigue and stress corrosion cracking (SCC) behavior of these steels by affecting the material microchemistry, material microstructure, and water chemistry. Experimental data are presented on crack growth rates of the heat affected zone (HAZ) in Types 304L and 304 SS weld specimens before and after they were irradiated to a fluence of 5.0 x 10{sup 20} n/cm{sup 2} (E > 1 MeV) ({approx} 0.75 dpa) at {approx}288 C. Crack growth tests were conducted under cycling loading and long hold time trapezoidal loading in simulated boiling water reactor environments on Type 304L SS HAZ of the H5 weld from the Grand Gulf reactor core shroud and on Type 304 SS HAZ of a laboratory-prepared weld. The effects of material composition, irradiation, and water chemistry on growth rates are discussed.
Chopra, O. K.; Alexandreanu, B.; Gruber, E. E.; Daum, R. S.; Shack, W. J.; Energy Technology
Microstructural response to heat affected zone cracking of prewelding heat-treated Inconel 939 superalloy
The microstructural response to cracking in the heat-affected zone (HAZ) of a nickel-based IN 939 superalloy after prewelding heat treatments (PWHT) was investigated. The PWHT specimens showed two different microstructures: 1) spherical ordered {gamma} Prime precipitates (357-442 nm), with blocky MC and discreet M{sub 23}C{sub 6} carbides dispersed within the coarse dendrites and in the interdendritic regions; and 2) ordered {gamma} Prime precipitates in 'ogdoadically' diced cube shapes and coarse MC carbides within the dendrites and in the interdendritic regions. After being tungsten inert gas welded (TIG) applying low heat input, welding speed and using a more ductile filler alloy, specimens with microstructures consisting of spherical {gamma} Prime precipitate particles and dispersed discreet MC carbides along the grain boundaries, displayed a considerably improved weldability due to a strong reduction of the intergranular HAZ cracking associated with the liquation microfissuring phenomena. - Highlights: Black-Right-Pointing-Pointer Homogeneous microstructures of {gamma} Prime spheroids and discreet MC carbides of Ni base superalloys through preweld heat treatments. Black-Right-Pointing-Pointer {gamma} Prime spheroids and discreet MC carbides reduce the intergranular HAZ liquation and microfissuring of Nickel base superalloys. Black-Right-Pointing-Pointer Microstructure {gamma} Prime spheroids and discreet blocky type MC carbides, capable to relax the stress generated during weld cooling. Black-Right-Pointing-Pointer Low welding heat input welding speeds and ductile filler alloys reduce the HAZ cracking susceptibility.
Gonzalez, M.A., E-mail: firstname.lastname@example.com [Facultad de Ingenieria Mecanica y Electrica (FIME-UANL), Av. Universidad s/n. Ciudad Universitaria, C.P.66451 San Nicolas de los Garza, N.L. (Mexico); Martinez, D.I., E-mail: firstname.lastname@example.com [Facultad de Ingenieria Mecanica y Electrica (FIME-UANL), Av. Universidad s/n. Ciudad Universitaria, C.P.66451 San Nicolas de los Garza, N.L. (Mexico); Perez, A., E-mail: firstname.lastname@example.com [Facultad de Ingenieria Mecanica y Electrica (FIME-UANL), Av. Universidad s/n. Ciudad Universitaria, C.P.66451 San Nicolas de los Garza, N.L. (Mexico); Guajardo, H., E-mail: firstname.lastname@example.com [FRISA Aerospace, S.A. de C.V., Valentin G. Rivero No. 200, Col. Los Trevino, C.P. 66150, Santa Caterina N.L. (Mexico); Garza, A., E-mail: email@example.com [Corporacion Mexicana de Investigacion en Materiales S.A. de C.V. (COMIMSA), Ciencia y Tecnologia No.790, Saltillo 400, C.P. 25295 Saltillo Coah. (Mexico)
Factors Affecting the Hydrogen Environment Assisted Cracking Resistance of an AL-Zn-Mg-(Cu) Alloy
Precipitation hardenable Al-Zn-Mg alloys are susceptible to hydrogen environment assisted cracking (HEAC) when exposed to aqueous environments. In Al-Zn-Mg-Cu alloys, overaged tempers are used to increase HEAC resistance at the expense of strength but overaging has little benefit in low copper alloys. However, the mechanism or mechanisms by which overaging imparts HEAC resistance is poorly understood. The present research investigated hydrogen uptake, diffusion, and crack growth rate in 90% relative humidity (RH) air for both a commercial copper bearing Al-Zn-Mg-Cu alloy (AA 7050) and a low copper variant of this alloy in order to better understand the factors which affect HEAC resistance. Experimental methods used to evaluate hydrogen concentrations local to a surface and near a crack tip include nuclear reaction analysis (NRA), focused ion beam, secondary ion mass spectroscopy (FIB/SIMS) and thermal desorption spectroscopy (TDS). Results show that overaging the copper bearing alloys both inhibits hydrogen ingress from oxide covered surfaces and decreases the apparent hydrogen diffusion rates in the metal.
G.A. Young; J.R. Scully
The stress corrosion cracking behavior of alloys 690 and 152 WELD in a PWR environment.
Alloys 690 and 152 are the replacement materials of choice for Alloys 600 and 182, respectively. The latter two alloys are used as structural materials in pressurized water reactors (PWRs) and have been found to undergo stress corrosion cracking (SCC). The objective of this work is to determine the crack growth rates (CGRs) in a simulated PWR water environment for the replacement alloys. The study involved Alloy 690 cold-rolled by 26% and a laboratory-prepared Alloy 152 double-J weld in the as-welded condition. The experimental approach involved pre-cracking in a primary water environment and monitoring the cyclic CGRs to determine the optimum conditions for transitioning from the fatigue transgranular to intergranular SCC fracture mode. The cyclic CGRs of cold-rolled Alloy 690 showed significant environmental enhancement, while those for Alloy 152 were minimal. Both materials exhibited SCC of 10{sup -11} m/s under constant loading at moderate stress intensity factors. The paper also presents tensile property data for Alloy 690TT and Alloy 152 weld in the temperature range 25--870 C.
Alexandreanu, B.; Chopra, O. K.; Shack, W. J. (Nuclear Engineering Division); ( EVS); ( ESE)
A Flaw Tolerance Approach to Address Reactor Vessel Head Penetration Cracking Issue
Nickel-based alloys and the associated welds are susceptible to Primary Water Stress Corrosion Cracking. In Pressurized Water Reactor nuclear power plants, the reactor vessel closure head upper penetration nozzles used for the Control Rod Drive Mechanisms and other instrumentation systems are made of such nickel-based alloys. Cracking and leakage have been observed in the upper head penetration nozzles in nuclear power plants worldwide. Such cracking and the resulting leakage is a degradation of the reactor vessel pressure boundary. Regulatory requirements have been issued by the Nuclear Regulatory Commission regarding periodic inspection of the susceptible areas to enable detection of indications and provide reasonable assurance of continued structural integrity for reactor vessel closure head. A flaw tolerance approach has been used in the disposition of detected indications to minimize outage delays, by performing up-front fracture mechanics evaluations for the common types of indications detected in the susceptible areas. Details of the flaw tolerance approach are presented in this paper. (authors)
Ng, C. K.; Jirawongkraisorn, S.; Swamy, S. [Westinghouse Electric Company, LLC, Nuclear Services Division, P. O. Box 158, Madison, PA 15663 (United States)
Results of crack-arrest tests on two irradiated high-copper welds
The objective of this study was to determine the effect of neutron irradiation on the shift and shape of the lower-bound curve to crack-arrest data. Two submerged-arc welds with copper contents of 0.23 and 0.31 wt % were commercially fabricated in 220-mm-thick plate. Crack-arrest specimens fabricated from these welds were irradiated at a nominal temperature of 288{degree}C to an average fluence of 1.9 {times} 10{sup 19} neutrons/cm{sup 2} (>1 MeV). Evaluation of the results shows that the neutron-irradiation-induced crack-arrest toughness temperature shift is about the same as the Charpy V-notch impact temperature shift at the 41-J energy level. The shape of the lower-bound curves (for the range of test temperatures covered) did not seem to have been altered by irradiation compared to those of the ASME K{sub Ia} curve. 9 refs., 21 figs., 10 tabs.
Iskander, S.K.; Corwin, W.R.; Nanstead, R.K. (Oak Ridge National Lab., TN (USA))
Linking Grain Boundary Microstructure to Stress Corrosion Cracking of Cold Rolled Alloy 690 in PWR Primary Water
Grain boundary microstructures and microchemistries are examined in cold-rolled alloy 690 tubing and plate materials and comparisons are made to intergranular stress corrosion cracking (IGSCC) behavior in PWR primary water. Chromium carbide precipitation is found to be a key aspect for materials in both the mill annealed and thermally treated conditions. Cold rolling to high levels of reduction was discovered to produce small IG voids and cracked carbides in alloys with a high density of grain boundary carbides. The degree of permanent grain boundary damage from cold rolling was found to depend directly on the initial IG carbide distribution. For the same degree of cold rolling, alloys with few IG precipitates exhibited much less permanent damage. Although this difference in grain boundary damage appears to correlate with measured SCC growth rates, crack tip examinations reveal that cracked carbides appeared to blunt propagation of IGSCC cracks in many cases. Preliminary results suggest that the localized grain boundary strains and stresses produced during cold rolling promote IGSCC susceptibility and not the cracked carbides and voids.
Bruemmer, Stephen M.; Olszta, Matthew J.; Toloczko, Mychailo B.; Thomas, Larry E.
Factors Affecting the Hydrogen Environment Assisted Cracking Resistance of an Al-Zn-Mg-(Cu) Alloy
It is well established that Al-Zn-Mg-(Cu) aluminum alloys are susceptible to hydrogen environment assisted cracking (HEAC) when exposed to aqueous environments. In Al-Zn-Mg-Cu alloys, overaged tempers are commonly used to increase HEAC resistance at the expense of strength. Overaging has little benefit in low copper alloys. However, the mechanism or mechanisms by which overaging imparts HEAC resistance is poorly understood. The present research investigated hydrogen uptake, diffusion, and crack growth rate in 90% relative humidity (RH) air for both a commercial copper bearing Al-Zn-Mg-Cu alloy (AA 7050) and a low copper variant of this alloy in order to better understand the factors which affect HEAC resistance. Experimental methods used to evaluate hydrogen concentrations local to a surface and near a crack tip include nuclear reaction analysis (NRA), focused ion beam, secondary ion mass spectroscopy (FIB/SIMS) and thermal desorption spectroscopy (TDS). When freshly bared coupons of AA 7050 are exposed to 90 C, 90% RH air, hydrogen ingress follows inverse-logarithmic-type kinetics and is equivalent for underaged (HEAC susceptible) and overaged (HEAC resistant) tempers. However, when the native oxide is allowed to form (24 hrs in 25 C, 40% RH lab air) prior to exposure to 90 C, 90% RH air, underaged alloy shows significantly greater hydrogen ingress than the overaged alloy. Humid air is a very aggressive environment producing local ({approx}1{micro}m) hydrogen concentrations in excess of 10,000 wt. ppm at 90 C. In the copper bearing alloy, overaging also effects the apparent diffusivity of hydrogen. As AA 7050 is aged from underaged {yields} peak aged {yields} overaged, the activation energy for hydrogen diffusion increases and the apparent diffusivity for hydrogen decreases, In the low copper alloy, overaging has little effect on hydrogen diffusion. Comparison of the apparent activation energies for hydrogen diffusion and for K independent (stage II) crack growth rate in 90% RH air between 25 and 90 C indicates that hydrogen transport kinetics are responsible for the decreased crack growth rate of overaged AA 7050 relative to the peak aged temper.
Stress Corrosion Cracking of the Drip Shield, the Waste Package Outer Barrier, and the Stainless Steel Structural Material
Stress corrosion cracking is one of the most common corrosion-related causes for premature breach of metal structural components. Stress corrosion cracking is the initiation and propagation of cracks in structural components due to three factors that must be present simultaneously: metallurgical susceptibility, critical environment, and static (or sustained) tensile stresses. This report was prepared according to ''Technical Work Plan for: Regulatory Integration Modeling and Analysis of the Waste Form and Waste Package'' (BSC 2004 [DIRS 171583]). The purpose of this report is to provide an evaluation of the potential for stress corrosion cracking of the engineered barrier system components (i.e., the drip shield, waste package outer barrier, and waste package stainless steel inner structural cylinder) under exposure conditions consistent with the repository during the regulatory period of 10,000 years after permanent closure. For the drip shield and waste package outer barrier, the critical environment is conservatively taken as any aqueous environment contacting the metal surfaces. Appendix B of this report describes the development of the SCC-relevant seismic crack density model (SCDM). The consequence of a stress corrosion cracking breach of the drip shield, the waste package outer barrier, or the stainless steel inner structural cylinder material is the initiation and propagation of tight, sometimes branching, cracks that might be induced by the combination of an aggressive environment and various tensile stresses that can develop in the drip shields or the waste packages. The Stainless Steel Type 316 inner structural cylinder of the waste package is excluded from the stress corrosion cracking evaluation because the Total System Performance Assessment for License Application (TSPA-LA) does not take credit for the inner cylinder. This document provides a detailed description of the process-level models that can be applied to assess the performance of Alloy 22 (used for the waste package outer barrier) and Titanium Grade 7 (used for the drip shield) that are subjected to the effects of stress corrosion cracking. The use of laser peening or other residual stress mitigation techniques is considered as a means of mitigating stress corrosion cracking in the waste package final closure lid weld.
G. Gordon
Product Price Spreads Over Crude Oil Vary With Seasons and Supply/Demand
6 6 Notes: Of course, petroleum product prices don't move in lockstep to crude oil prices, for a number of reasons. We find it useful to look at variations in the spread between product and crude oil prices, in this case comparing spot market prices for each. The difference between heating oil and crude oil spot prices tends to vary seasonally; that is, it's generally higher in the winter, when demand for distillate fuels is higher due to heating requirements, and lower in the summer. (Gasoline, as we'll see later, generally does the opposite.) However, other factors affecting supply and demand, including the relative severity of winter weather, can greatly distort these "typical" seasonal trends. As seen on this chart, the winters of 1995-96 and 1996-97 featured
Investigation of possible csr induced energy spread effects with the A0 photoinjector bunch compressor
The bunch compressor of the A0 Photoinjector at Fermilab was removed this past spring to install a transverse to longitudinal emittance exchange experiment. Prior to its removal questions arose about the possibility of observing the effects of Coherent Synchrotron Radiation on the compressed beam. The energy spread of the beam with and without compression was measured to observe any changes. Various beam charges were used to look for square law effects associated with CSR. No direct observation of CSR in the compressor was attempted because the design of the vacuum chamber did not allow it. In this paper we report the results of these experiments and comparison with simulations using ASTRA and CSRTrack. The results are also compared with analytical approximations.
Fliller, R.P., III; Edwards, H.; Kazakevich, G.; Thurman-Keup, R.M.; Ruan, J.; /Fermilab
Energy spread inhibition of compact electron bunch driven by circularly polarized laser pulse
The problem of energy dispersion of a direct laser accelerated electron bunch emerging from a nano-meshed graphene target is investigated. To study the effects of the laser polarization state on the energy spread, numerical calculations and particle-in-cell simulations of evolving one-dimensional confined electron bunch dynamics are performed. It is proved that a circularly polarized laser pulse can inhibit energy dispersion more efficiently than a linearly polarized laser pulse with the same laser and target parameters. That is because the Coulomb expansion of the electron bunch gets more attenuated for a circularly polarized laser pulse compared with a linearly polarized pulse due to the slowly varying temporal laser intensity.
Wen Meng [State Key Laboratory of Nuclear Physics and Technology, and Key Lab of High Energy Density Physics Simulation, CAPT, Peking University, Beijing 100871 (China); Institute of Photonics and Photon-Technology, Northwest University, Xi'an 710069 (China); Wu Haicheng; Lu Yuanrong; Chen Jiaer; Yan, Xueqing [State Key Laboratory of Nuclear Physics and Technology, and Key Lab of High Energy Density Physics Simulation, CAPT, Peking University, Beijing 100871 (China); Jin Luling [Department of Physics, Northwest University, Xi'an 710069 (China)
Measurement of rising R-curve behavior in toughened silicon nitride by stable crack propagation in bending
A simple procedure for measuring the R-curve properties of ceramics by a stable fracture test in three-point bending is described. As a typical case, data are displayed for a Si{sub 3}N{sub 4} material toughened by the presence of acicular grains in situ grown during the sintering process. The fracture mechanics specimen was a single-edge double-notched beam (SEDNB), whose notch was sharpened to a radius of < 10 {micro}m in order to reduce the amount of elastic energy stored at its root prior to crack extension. Furthermore, a stabilizer, specially designed for the bending geometry, was used to control crack stability. During stable extension, the crack could be easily arrested at selected locations of the load-displacement curve, the load quickly released, and the stable crack extension directly measured by the die-penetration technique. The crack resistance, K{sub R}, of the material was calculated from the measured crack extent and the onset load value before unloading. This method enabled them to precisely monitor the critical load value at which the load-displacement curve deviated from linear behavior, as well as crack extensions from a few tens of micrometers to about 1 mm. As an application of this method, the fracture resistance of a Si{sub 3}N{sub 4} material with rising R-curve behavior was measured and found to increase from about 5.5 to 9.0 MPa {center_dot} m{sup 1/2} within a 0.8-mm extension.
Nishida, Toshihiko; Hanaki, Yoshikazu [Kyoto Inst. of Tech. (Japan). Dept. of Materials; Nojima, Taketoshi [Kyoto Univ. (Japan). Dept. of Aeronautical Engineering; Pezzotti, G. [Toyohashi Univ. of Technology (Japan). Dept. of Materials Science
Materials Reliability Program: Determination of Crack Growth Rates for Alloy 82 at Low K Values Under Pressurized Water Reactor Prim ary Water Environment (MRP-270)
Crack propagation experiments, which were performed in the past on nickel-based materials under PWR primary water environment, have left some open questions that need to be answered. In particular, no crack growth rate (CGR) data for control rod driving mechanism (CRDM) nozzle materials are available at low stress intensity (K) values (K < 15 MPam). This interim report summarizes the work done during 2009 on a cooperative project to generate crack growth data under low K values for alloy 82 weld metal.
The Effects of Test Temperature, Temper, and Alloyed Copper on the Hydrogen-Controlled Crack Growth Rate of an Al-Zn-Mg-(Cu) Alloy
The hydrogen embrittlement controlled stage II crack growth rate of AA 7050 (6.09 wt.% Zn, 2.14 wt% Mg, 2.19 wt.% Cu) was investigated as a function of temper and alloyed copper level in a humid air environment at various temperatures. Three tempers representing the underaged, peak aged, and overaged conditions were tested in 90% relative humidity (RH) air at temperatures between 25 and 90 C. At all test temperatures, an increased degree of aging (from underaged to overaged) produced slower stage II crack growth rates. The stage II crack growth rate of each alloy and temper displayed Arrhenius-type temperature dependence with activation energies between 58 and 99 kJ/mol. For both the normal copper and low copper alloys, the fracture path was predominantly intergranular at all test temperatures (25-90 C) in each temper investigated. Comparison of the stage II crack growth rates for normal (2.19 wt.%) and low (0.06 wt.%) copper alloys in the peak aged and overaged tempers showed the beneficial effect of copper additions on stage II crack growth rate in humid air. In the 2.19 wt.% copper alloy, the significant decrease ({approx} 10 times at 25 C) in stage II crack growth rate upon overaging is attributed to an increase in the apparent activation energy for crack growth. IN the 0.06 wt.% copper alloy, overaging did not increase the activation energy for crack growth but did lower the pre-exponential factor, {nu}{sub 0}, resulting in a modest ({approx} 2.5 times at 25 C) decrease in crack growth rate. These results indicate that alloyed copper and thermal aging affect the kinetic factors that govern stage II crack growth rate. Overaged, copper bearing alloys are not intrinsically immune to hydrogen environment assisted cracking but are more resistant due to an increased apparent activation energy for stage II crack growth.
G.A. Young, Jr.; J.R. Scully
BWRVIP-212: BWR Vessel and Internals Project, Evaluation of Crack Growth Rates of Nickel-Base Alloys 52, 152, and 690 in BWR Enviro nments
This study summarizes available information on stress corrosion cracking (SCC) performance of high-chromium, nickel-base (Ni-base) alloys in boiling water reactor (BWR) environments.
Hot ductility and hot cracking behavior of modified 316 stainless steels designed for high-temperature service
The weldability of the modified 316 stainless steel was evaluated by the Gleeble hot ductility test and two hot cracking test methods (Varestraint and Sigmajig). The fusion zone and weld metal heat-affected zone (HAZ) hot cracking susceptibilities of the modified 316 stainless steel are similar to conventional fully austenitic 316 stainless steels and greater than the conventional 316 materials that have a primary ferritic solidification mode. The Gleeble hot ductility test results correlate with the base metal HAZ hot cracking results from the Varestraint test and indicate that the modified 316 materials show a considerably higher base metal HAZ hot cracking susceptibility as contrasted to nuclear grade 316 stainless steels. Varestraint test results and Sigmajig test results and Sigmajig test results for the tested materials showed good correlations. The sensitivity of the base metal to HAZ liquation cracking has been successfully predicted by using a newly developed hot ductility criterion, the ratio of ductility recovery (RDR). An excellent correlation between the Gleeble Test criterion RDR and the Varestraint Test criteria (TCL, MCL and CHL) has been found.
Lundin, C.D.; Qiao, C.Y.P.; Gill, T.P.S.; Goodwin, G.M. (Oak Ridge National Lab., TN (United States))
Developing Fatigue Pre-crack Procedure to Evaluate Fracture Toughness of Pipeline Steels Using Spiral Notch Torsion Test
The spiral notch torsion test (SNTT) has been utilized to investigate the crack growth behavior of X52 steel base and welded materials used for hydrogen infrastructures. The X52 steel materials are received from a welded pipe using friction stir welding techniques. Finite element models were established to study the crack growth behavior of steel SNTT steel samples, which were assumed to be isotropic material. A series SNTT models were set up to cover various crack penetration cases, of which the ratios between crack depth to diameter (a/D ratio) ranging from 0.10 to 0.45. The evolution of compliance and energy release rates in the SNTT method have been investigated with different cases, including different geometries and materials. Indices of characteristic compliance and energy release rates have been proposed. Good agreement has been achieved between predictions from different cases in the same trend. These work shed lights on a successful protocol for SNTT application in wide range of structural materials. The further effort needed for compliance function development is to extend the current developed compliance function to the deep crack penetration arena, in the range of 0.55 to 0.85 to effectively determine fracture toughness for extremely tough materials.
Wang, Jy-An John [ORNL; Tan, Ting [ORNL; Jiang, Hao [ORNL; Zhang, Wei [ORNL; Feng, Zhili [ORNL
Interference of wedge-shaped protrusions on the faces of a Griffith crack in biaxial stress. Final report
An initial investigation of the influence of protrusion interference on the fracture toughness required to prevent unstable propagation of a Griffith crack in a brittle material is described. The interference is caused by relative shear displacement of the crack faces when subjected to remote biaxial stress with neither principal stress parallel to the crack. It is shown that for room temperature cracks smaller than about one centimeter in silicon carbide, or about one millimeter in silicon nitride, the presence of interference changes the fracture stress. A mathematical model based on linear elasticity solutions and including multiple interference sites at arbitrarily specified positions on the crack is presented. Computations of the change in required fracture toughness and its dependence on wedge geometry (size and vertex angle), applied stresses (orientation and magnitude), and location of the interference site are discussed. Results indicate that a single interference site has only a slight effect on required toughness. However, the influence of interference increases monotonically with the number of interference sites. The two-dimensional model described herein is not accurate when the interference sites are closely spaced.
Boulet, J.A.M. [Tennessee Univ., Knoxville, TN (United States)
Circumferential Cracking Investigation on a Supercritical Boiler � Martin Lake Unit 3
Luminants Martin Lake unit 3 is one of three supercritical boilers at the site. Lignite from nearby mines is the principal source of fuel, which is mixed with 10-20% Powder River Basin or western coal to assist combustion. The boiler was originally designed to generate around 750 MW, although it is now generating up to 850 MW. In 2000, water cannons were installed in the walls as a replacement for the wall blowers. At about the same time, after 21 years of operation without signs of cracking, the unit wa...