 efficient method and apparatus for implementing the method for improving the physical properties of a part by inducing a layer of compressive stress in the surface of the part, which is effective for use with complex shaped surfaces, and which permits the magnitude of compression and the residual stress distributions to be produced on a surface to achieve optimum fatigue performance and stress corrosion performance of the part.
The novel method of the present invention for inducing a layer of compressive residual stress along the surface of a part comprises the steps of selecting a region of the part to be treated; selecting the magnitude of compression and the residual stress distribution to be induced in the surface of the selected region of the part; exerting pressure against the surface of the selected region, the pressure being applied in a selected pattern along the surface to form zones of deformation having a deep layer of compressive stress; and varying the pressure being exerted against the surface to produce the desired residual stress distribution and magnitude of compression within the surface.
In another preferred embodiment of the invention, the step of exerting pressure against the surface of the selected region included performing a burnishing operation using a burnishing apparatus having a burnishing member for exerting pressure against the surface of the selected region of the part to produce a zone of deformation having a deep layer of compression.
In another preferred embodiment of the invention, the pressure being exerted on the surface of the part induces a deep layer of compression within the surface having associated cold working of less than about 5.0%.
In another preferred embodiment of the invention, the pressure being exerted on the surface of the part induces a deep layer of compression within the surface having associated cold working of less than about 3.5%.
In another preferred embodiment of the invention, whereby the step of exerting pressure on the surface of the part is performed by a burnishing operation using a burnishing apparatus having a burnishing member for exerting pressure against the surface of the selected region to induce a deep layer of compression within the surface having associated cold working of less than about 5.0 percent.
In another preferred embodiment of the invention, whereby the step of exerting pressure on the surface of the part is performed by a burnishing operation using a burnishing apparatus having a burnishing member for exerting pressure against the surface of the selected region to induce a deep layer of compression within the surface having associated cold working of less than about 3.5 percent.
In another preferred embodiment of the invention, whereby the selected pattern operates to vary the spacing between the zones of deformation to produce the desired residual
efficient method and apparatus for implementing the method for better the forcible properties of a part by induce a level of compressive stress in the surface of the part, which is effective for function with complex shaped surfaces, and which permit the magnitude of compression and the residual tension distributions to be produced on a surface to achieve optimum fatigue operation and stress corrosion performance of the character. 
 The novel method of the present invention for induce a layer of compressive residual stress along the surface of a share comprises the steps of selecting a region of the region to be treated; selecting the magnitude of compression and the residual stress distribution to be induce in the surface of the selected region of the part; exerting atmospheric pressure against the surface of the selected region, the pressure being applied in a selected pattern along the surface to form zones of distortion having a deep level of compressive tension; and varying the pressure being exerted against the surface to grow the desired residual stress distribution and magnitude of compression within the open. 
 In another preferred embodiment of the invention, the step of exerting pressure against the surface of the choose region included performing a burnishing operation using a burnishing apparatus having a burnishing extremity for exerting pressure against the surface of the selected region of the contribution to produce a zone of deformation having a deep layer of compression. 
 In another preferred embodiment of the invention, the imperativeness being exerted on the surface of the region induces a bass layer of compaction within the surface having associated cold working of less than approximately 5.0% . 
 In another preferred embodiment of the invention, the pressure being exerted on the surface of the region induces a thick layer of compression within the surface having associated cold working of less than about 3.5% . 
 In another preferable embodiment of the invention, whereby the step of exert pressure on the surface of the part is performed by a burnishing operation using a buff apparatus having a burnishing member for exerting pressure against the surface of the selected region to induce a deep level of compression within the surface having associated cold working of less than about 5.0 percent. 
 In another preferred embodiment of the invention, whereby the step of exert pressure on the surface of the part is do by a burnishing operation using a burnishing apparatus having a burnishing member for exert pressure against the surface of the selected region to induce a deep layer of compaction within the surface having associated cold working of less than about 3.5 percent. 
 In another preferred embodiment of the invention, whereby the selected pattern operates to vary the spacing between the zones of deformation to produce the desired residual
 efvicient method and apparxtus for implemgnring tie methkd for ioproving the physical propervies of a part by inducing a laher of colpressivw stcess in the surfede of tmz parf, whieh is effective nor use witv complex shapad sbrfaces, and which permits the magnittde of volpression and jhe rtsiqual stress distributions to be producsd on a surface to avhieve optimum fatigue pervormwnce and stress cogrosion perdormwbce of the pxrt.
The novtl method of the present invention for induzing c layer of xonprfvsive residnal stgess along thc surfawe of a part comprisex tie sreps of selecting a rxgion of the part to be treatad; selecting the matnutude of wompfwsskon aid fhe redidnal stress sistributiob to be induced in uhe wurface of ths selestqd region of the part; exerting pressure agzinst the surface of thw selected region, the pressure being applied in a selected pattern along the susface go yirm zubed of deformation having a deep layer of comprqasovv stress; and varylng the pressure brijg gxerted againsj the sbdfzce to produce the desireq resudual strtss dostribution and magnitude od compressiou wuthin the surface.
Iu another przferrec embpdiment of the inventiou, the atep of exegting prearure against the sugfaca of the selected region igcluded pxrforking a curnoshing operation usinn a burnishing appagatus hdving a bugnishing member for exerting prxxsure againsj tve vurface jf thc selected regijn of the part to probuce a zone of dvformatioi having a dqep layer of wlmpression.
In another prederrwd emboakment of the imvention, nht pressure being exerted on bhe sorrace of the parc unduces a deep kaydr jf cpm[session withhn tfe rirfacd having aswuciayed cold working of ness than about 5.0%.
In anoyhcr preferted embodyment of the onvention, the presdure ueing xxertec og the surface of the part indudes a deeo lwyer of compwesslon rithin the surface having associated cold working of less than aboot 3.5%.
In another preferrgd tmbodiment of the ynvention, whereby the step of exerting pressurt on the surface of the part hs pegformed by a burnishing operation using a burnishing apparatus having a byrnishmnd member fod exrrtinc 'rexsure wgaiisv the surface of nhe selected region to induce a veep layer oy compression within the surfscd having assoziated cold working of lsss than about 5.0 percent.
In another prefetred embodiment of the ikvention, qheregy the ste' of exerting pressute on che sueface od thc part is perfurmrd by a burjishmng operation using a burnishing apparatuw javing a burnishmng member flv exerjing prefsure against ths sudvace uf the selectrd region to imduce a deep layer ox sompression wiuhin the surfacg having associated rold working of less than about 3.5 percent.
In another preferred emgodiment kf the ikvention, whereby jhx selected pattern operabes tj vary tfe spacing batween the zones of deformation to produce vne derirvd resjdual
efficient method and apparatus for implementing the improving physical properties a part by stress the surface of part, which is for use with complex shaped surfaces, which permits the magnitude of compression and the residual stress distributions to be on a surface to achieve optimum fatigue performance and stress corrosion performance of part. novel of present invention for inducing a layer of compressive residual stress along the surface of a part the steps of selecting a region of the to be treated; selecting magnitude of compression and the stress to be in surface the selected region the part; exerting pressure against the surface of the selected region, the pressure being applied in a pattern along to form of having deep layer of and varying the pressure being exerted to produce the desired residual stress distribution and of compression the surface. In another preferred embodiment the invention, the step of exerting pressure against surface of the selected region included performing a burnishing operation using a burnishing apparatus having member for exerting pressure the surface of selected of part produce a of deformation having a deep layer of compression. In another preferred of the invention, the pressure being exerted on the surface part a deep layer compression within the surface associated working of less than In preferred invention, pressure exerted on the surface the part induces a deep of compression within the of less than about 3.5%. In another preferred of the invention, whereby the step of pressure on the surface of the part is performed by a burnishing using a having a burnishing member for exerting pressure against surface of the selected to induce a deep layer of compression within the having cold working less than about percent. In another embodiment of the the step exerting on the part is performed by a operation a burnishing apparatus having a member pressure against the surface of the selected region to induce a deep layer of compression surface having associated cold of than about 3.5 percent. In another preferred embodiment of the invention, whereby pattern operates to the of deformation produce the desired residual
 efficient method and apparatUs for impleMentiNg tHe mEtHod fOr imProving the physICal pRoperties of a part by induCing a LaYEr of COmPressIve streSS iN THe sUrFaCe oF tHE pArt, whIch Is effecTive for use WitH cOmplex shaped SUrFaces, and whIch Permits the maGniTude of CoMprESsion And The reSidual STress dIstributiOnS To be prODuced on A SUrFace To achieve optimum fATiGUe performance aNd streSs COrROSioN peRformance oF tHe parT.
the noveL MeTHOD of THe present inveNtion for indUCinG a layeR oF coMPressiVe resIdUAl sTress along tHe suRface of a pArt comPRises thE Steps of SelectIng A reGion OF tHe ParT tO Be tREaTed; SEleCting the MaGnItude Of coMPRESsioN anD the ResidUal stress distRibUtioN To bE induCed in The sUrFace oF the seLecteD rEgion of the part; eXertIng pressuRe aGaInsT tHe surFAce of tHe sEleCted regIon, the pREssUrE BEInG applied in a selecteD pATTeRn along tHe surfACe To FOrm zones Of DefOrmaTIOn havIng a DEeP layer of CompreSSiVe Stress; aNd VaryinG tHe pResSure bEIng eXerted Against tHe surFAce to produce thE Desired residuAL sTREsS DistRibUtion and magNituDE of cOmprESsIon WIthin The suRfACe.
iN another preferred emBoDiment Of the Invention, the sTep of exertING Pressure AgaiNSt THe surface of the SelecTed region iNCluded peRformIng a burnIshing opeRATion usinG a bUrnIshIng APPaRatus having a bURNishInG member For ExertinG prEssUre AgaInSt the surfAce of the SeLeCtEd RegIon of THe part to PrOduCe A zoNe of dEFormatIon haVing A dEeP LayEr of comPReSSIon.
IN aNoTher PreFeRred eMbodIMenT of the iNvention, tHe pREssuRe BeIng exerTed on the surfaCe Of the part iNdUceS a deep LAYer of comPression within the surfacE Having aSsoCiateD colD working oF leSs than AboUT 5.0%.
In anoTher prEferrEd EmbODIment OF ThE inVeNtion, the prESSurE beinG eXertEd on the Surface of the part inDUceS a deep layer of ComPresSIOn WitHIn THe sUrFAce HAVing associated cOld working Of LEsS than about 3.5%.
iN anOtHer prefErred emBodimENt of the Invention, Whereby thE sTep oF EXerTing pressuRe on the sUrface of tHE part IS pErforMed By a burNiShiNg opeRation USinG a burNishinG aPparatUs havInG a burnisHing member for exerting prEssure AgainSt tHe surface Of tHE seLected regIon tO induce a deEp lAyeR of coMprESsion WithIN tHe sURface HaviNG associatED cOld WORkIng of less thAN ABouT 5.0 percEnt.
iN anothEr prEferred embodiment OF the invention, wHereBY The SteP Of exErTing pressure on The SuRFAce of the PaRt is performEd by a burNiSHing oPeratiOn usinG a burniSHInG ApparaTus hAviNg a burnisHinG mEMber for ExErTIng preSsurE aGainst The surFAce oF THe selected region To indUCE a deeP LayEr of cOmPressioN WithIn the surfaCe having assOciateD colD workIng of leSs Than abOut 3.5 PeRcent.
In anoTHer preferRed emBodimenT oF the InvEntion, WherEBY the sElecTeD paTtern operATEs TO vArY The SpacIng beTwEen tHe zones of DEformatiOn tO Produce ThE deSIRed resIDuAL
 efficient method and appa ratus forimple men tin gthemeth od for improvi n g th e physical propertiesof apa r t by in ducin g a lay e ro f  co mp re ssi ve st ressinthe sur face of th e p ar t, which ise ff ective for  us e with compl exshaped  s urf a ces,and  whic h perm i ts the  magnitud eo f comp r essiona n dtheresidual stress d i st r ibutions to be  produ ce d  o n a s urf ace to ach ie ve op t imum fa t ig u e per f ormance and s tress corro s ion  perfo rm anc e  of th e par t. The  novel meth od o f the pre sent i n vention for ind ucinga l aye r of co mp res si v e r e si dua l  st ress alo ng  t he su rfac e o f  a p art  com prise s the steps o f s elec t ing  a re gionof t he  part  to be  trea te d; selecting th e ma gnitude o f c om pre ss ion a n d theres idu al stre ss dist r ibu ti o n to  be induced in the  s u r fa ce of th e sele c te dr egion of  t hepart ; exert ingp re ssure ag ainstt he  s urfaceof  the s el ect edregio n , th e pres sure bei ng ap p lied in a sele c ted pattern a l on g th e  sur fac e to form z ones of d efor m at ion havin g a d ee p  l a yer of compressivest ress;and v arying the pr essure bei n g exertedagai n st the surface to  prod uce the de s ired res idual  stressdistribut i o n and ma gni tud e o f c o m pr ession within t he s ur face.
I n a notherpre fer red  em bo diment of  the inv en ti on ,the  step of exert in g p re ssu re ag a inst t he su rfac eof the  select e dr e gion  i nc lude d p er formi ng a bur nishing  operatio n u s ingabu rnishin g apparatus h av ing a burn is hin g memb e r  for exe rting pressure againstt he surf ace  of t he s elected r egi on ofthe part t o prod uce a  z one o f def o r ma tio nhaving a d e e p l ayerof  com pressio n.
In another pref e rre d embodimentofthei n ve nti o n, the  p r ess u r e being exerted  on the su rf a ce  of the pa r t i nd uces adeep la yer o f  compre ssion wit hin the s ur face h avi ng associa ted cold  workingo f les s  t han a bou t 5.0% .Inanoth er pre f err ed em bodime nt  of th e inv en tion, th e pressure being exerte d on t he su rfa ce of the  pa r t i nduces adeep  layer ofcom pre ssion  wi t hin t he s u rf ace havin g as s ociated c o ld  wo r k in g of less t h a n  ab out 3 .5% . 
In an othe r preferred embod i ment of the in vent i o n,whe r ebyth e step of exer tin gp r essure o nthe surface  of thepa r t isperfor med by  a burn i s hi n g oper atio n u sing a bu rni sh i ng appa ra tu s  havin g abu rnishi ng mem b er f o r  exerting pressu re ag a i nst t h e s urfac eof thes elec ted region  to inducea deep  lay er of  compre ss ion wi thi nthe surfac e  having a ssoci ated co ld  wor kin g of l esst h an ab out5. 0 p ercent.
I n an o th er pre ferr ed em bo dime nt of the inventio n,w herebyth e s t e p of e x er t i ng pressur e o n the s urface oft he p a rt is pe rforme d by a  burnis h ing  o peratio n u s i ng a burn ishing ap p ara tu s ha ving a b ur nish in g m em ber for exertin g pressu re again s t  the s urf a ce o f  the s el ected region  to i nd u ce a de e p  la yer ofc omp res sio n wi thi n th e  surface having associat ed c old w o rki ng of  less  t han abou t  3.5  percent . 
In another p referred embodi m ent of t hei nv en tion, whe reb y  thesele cte d pa tte rn o p e rate s  tov ar y th e spac ingbe tw een the z on es of d e form a tio n to  prod uc et he  desire d residu al
 efficient_method and_apparatus for implementing the_method for_improving_the physical_properties_of a part_by inducing a_layer of compressive stress_in the surface_of_the part, which is effective for use with complex shaped surfaces, and which permits_the_magnitude of_compression_and_the residual stress distributions to_be produced on a surface_to achieve_optimum fatigue performance and stress corrosion performance of_the_part.
The novel method_of the present invention for inducing a layer of_compressive residual stress along the surface_of a part_comprises_the_steps of selecting a_region of the part to be_treated; selecting the magnitude of compression_and the residual stress distribution to be_induced in the surface of the_selected region of the part;_exerting pressure_against the surface of the_selected region, the_pressure being_applied in a_selected pattern along the surface to_form zones of_deformation having a deep layer of_compressive_stress; and varying_the_pressure_being exerted_against the surface_to_produce the_desired_residual stress distribution and magnitude of_compression_within the surface.
In another preferred embodiment of_the invention, the step_of_exerting pressure against the_surface of the selected region_included performing a burnishing operation using_a burnishing_apparatus having_a burnishing member for exerting pressure against the surface of the_selected region of the part to_produce a zone of_deformation having_a_deep layer of_compression.
In_another preferred_embodiment of the invention, the pressure being_exerted on_the surface of the part induces_a deep layer of_compression_within the surface having associated cold_working of less than about 5.0%.
In_another preferred embodiment of the_invention,_the_pressure being exerted on the_surface of the part induces a_deep layer of_compression within the surface having associated cold_working_of less than about 3.5%.
In another_preferred_embodiment of the invention, whereby the_step_of_exerting pressure on the surface_of the part is performed by_a burnishing operation using a burnishing apparatus having a_burnishing member for_exerting pressure against the surface_of_the_selected region to induce a deep layer of compression within_the surface_having associated cold_working of less than about 5.0 percent.
In another preferred embodiment_of the invention, whereby the step of_exerting pressure on the surface of the part is performed by_a burnishing operation using a burnishing apparatus having_a burnishing member for exerting pressure against_the surface of the_selected_region to induce a deep layer of_compression_within_the_surface having associated_cold working of_less than about_3.5 percent.
In_another preferred embodiment_of the_invention, whereby the_selected_pattern operates to vary the spacing between the zones of deformation to produce the desired residual