fixed大旗网论坛
大旗网论坛 时间:2021-02-23 阅读:()
TherecentdevelopmentsofshotpeeninginChinaKeweiXu1,ChuanhaiJiang2,RenzhiWang31SchoolofMaterialscienceandengineering,Xi'anJiaotongUniversity,Xi'an,7100492SchoolofMaterialscienceandengineering,ShanghaiJiaotongUniversity,Shanghai,2002403InstituteofAeronauticalMaterials,Beijing,100095Abstract:WiththedevelopmentofChineseindustry,shotpeeningtechnologyiswidelyusedinmachinerymanufacturingindustryinChinainrecentdecade.
ThispapergivesabriefintroductionofdevelopmentofshotpeeningindustryinChina,whichincludesshotpeeningequipmentandpeeningmediamanufacturing,processplanningaboutshotpeeningandapplicationfieldsofdifferenttypesofshotpeening.
Intermsofbasicresearchofshotpeening,thispapersummarizessomenotableresearchresultsaboutstressstrengtheningandmicrostructurestrengtheningofshotpeening,influenceofshotpeeningonfatiguelifeofspecificmaterial,resistancetosomeformsofstresscorrosionandsoon.
Furthermore,applicationofconventionalshotpeeningtreatmentonadvancedmaterials,newshotpeeningtechniqueandcomputermodelingtechniqueaboutshotpeeningprocessalsodevelopveryrapidlyinChina.
Keywords:Shotpeening,Development,ChinaIntroductionPeeningmachine(PM),peeningshot(PS)andpeeningtechnologies(PT)arethreeveryimportantfactorsofshotpeening(SP)treatmenttechnologiesforworkpieces.
TherelationshipbetweenthesethreefactorshasbeenshowninFig.
1.
Fig.
1.
ThreefactorsofSPtreatmenttechnologiesforworkpiecesandtherelationshipwitheachother.
PS/PTPM/PS/PTPMPSPM/PSPM/PTPTSPtreatmenttechnologiesworkjustlikeamedicine,whichcantreatandimprovethefatiguefractureresistance(FFR)andstresscorrosioncrackingresistance(SCCR)ofmechanicalworkpieces.
Inordertoobtaintheoptimumstrengtheningeffect,thePMandPSmustfulfillalltherequirementsofPTdecidedbyworkpieces,suchaslocationsofSP,SPintensities,coverageofsurface,roughnessofSPandsoon.
AfterSP,thestructuresofsurfacelayersofworkpiecesarechangedasfollows:circulatingstrainhardeningofsurfacestructureandintroducedcompressiveresidualstress,whichcanimproveFFRandSCCRofmaterials/workpiece(M/W)accordingtostructurehardeningmechanismandresidualstresshardeningmechanismrespectively,besides,circulatingstrainrelaxationofsurfacestructureandincrementofsurfaceroughnesscanreduceFFRandSCCRofM/Wtoacertainextent.
ThevariationshavebeenshowninFig.
2.
TheSPtreatmentsofM/WshoulddependonfinePMandPStoobtaincompositestrengtheningeffectsofthevariationsmentionedinFig.
2tothemostdegree.
Fig.
2.
ThechangesofworkpiecesinsurfacelayersafterSPAccordingtothethreefactorsmentionedinFig.
1,combinethedevelopmentofSPinChinaandeachfactorwillbepresentedasfollows.
1.
ThedevelopmentofPMmanufacturePMismainlyusedtomodifyandimproveFFRandSCCRofM/W.
AndmanufacturecompaniesdesignandfabricatePMaccordingtofollowbasicprinciples.
(1)Basedonthematerials,shape,size,peeninglocation,etaltodesignthePM.
(2)Basedontherisklocationstendedtofatiguefracture,andspecialSPparameters(SPintensities,surfacecoverage,shottype,sizeandhardness)todesignthePM.
(3)InordertoimprovethestabilityandrepeatofSPparameters,theshotdiameterfilter,thecrackedshotsegregator,themonitorofshotvelocityandflux,andotheraccessoriesshouldbefixedinPM.
ChangesofsurfaceroughnessIncreaseofsurfacestressconcentratecoefficientKtDecreaseofsurfacestressconcentratecoefficientKtIntroduceresidualstressinsurfacelayersTensileresidualstressindeepsurfaceCompressiveresidualstressintopsurfaceDynamiccirculatingstrainhardeningofstructureDynamiccirculatingstrainintenerateofstructureVariationsofsurfacelayerofM/WafterSP(4)Accordingtotheoutput,geometricshape,size,andeconomicbenefitofworkpieces,considerwhichtypePMwillbechose,airblasttypePMormechanicaltypePM.
Basedonaboveprinciples,manytypesofPMhavebeenmanufacturedinlatest20years.
Somerepresentativetypeshavebeendisplayedasfollows.
(1)SpecialairblasttypePMdesignedforSPonaircraftengines,turbinediscandturbineblade.
(2)SpecialairblasttypePMdesignedforSPonlandinggearworkpieces.
(3)SpecialPMdesignedforSPoninner-hollow(Φ120mm)longaxes(1700mm).
(4)SpecialmechanicaltypePMdesignedforSPonlongsuckers(8m)usedinoilwell.
(5)SpecialPMdesignedforSPonsuspensionspring,valvespringandtunnelworkpieces.
(6)Specialcomputerizednumericalcontrol(CNC)airblasttypePMdesignedforSPongasturbinebigblade.
(7)AirblasttypeandmechanicaltypePMdesignedforSPonsomekindsofgears.
Recently,thecombiningresearchesbyShanghaiCarthingMachinaryCo.
,Ltd(Shanghai,China)andShanghaiJiaoTongUniversity(Shanghai,China)makefive-shaftdiveCNCairblasttypePMmanufactured,andwhichmakesthehighaccurateCNCPMhomebredfirstly.
Afterthat,ShanghaiCarthingMachinaryCo.
,LtdhasmanufacturedtherobotcontrolledCNCPM,usingtherobotsonPMsuccessfully.
Andnow,SomeCNCPMsmadeinChinahavebeenexportedtoIndia,Turkeyandothercountries.
Certainly,itisjusttheinitialdevelopmentofCNCPMinChina,andthereisabiggapbetweendevelopedcountries.
Wewillhavealongwaytogocomparedwithforeigndevelopments.
2.
ThedevelopmentofPSmanufactureIn1950's,afewdepartmentsofindustry(eg.
aerialindustry)hadstartedusingPT.
Early,thematerialofPSwascaststeel,thentheglassbeadswereintroducedasshotmediaforaircraftenginesworkpieces.
ThepeeningcaststeelshotsaccordedwithSAEJ444astylehadbeenmanufacturedin1970'sinChina.
ShandongKaiTaiIndustrialTechnologiesCo.
,LtdisthebiggestcompanyinChina,andthefourthbiggestcompanyintheword.
Intherecentdecade,withthefastdevelopmentofautomobileindustry,thedemandsofcuttingsteelshotsbecomemoreandmorein-country.
SomecompanieslikeJiangsuDaQiGroupCo.
,Ltd.
astheheadcanmanufacturethousandstonsofcuttingsteelshotseachyearwhichareconsistentwiththestandardofSAEJ441,AMS2431,MIL-S-13165C,VDFI8001andDIN8201.
Thesecuttingsteelshotscanbefulfillednotonlythedemandofin-countrycompanies,butalsoexportedtothemarketofEurope.
3.
ThedevelopmentofPTmanufactureIn1960's,theinfluenceofSPonthefatigueandfracturepropertiesatelevatedtemperatureofNi-basedhightemperaturealloyshavebeeninvestigatinginsystem,andthePThadbeenusedonturbinebladeandaircraftenginessuccessfullyaccordingtoaboveinvestigations.
Theinvestigationscanreducetroublesofturbinebladeandprolongtheuselifeindouble.
Theindustrystandardof"TheIllustrationofShotPeeningTechnologiesofAircraftWorkpieces"(HB/Z26-92)designedbyaircraftmanufactureisthefirstaeronauticalandspaceflightindustrystandardofP.
R.
China.
Inrecent40years,theexperimentalstudyofappliedfundamentaltheoryofPThasbeenshowninfollowthreefacets.
3.
1Theexperimentalstudyoffatigueandfractureofmetalengineeringmaterials(1)Accordingtotheinvestigationonfatiguecrackinitiationofengineeringmaterials,microprocesstheoryoffatiguecrackinitiationhasbeenproposed[1].
(2)Accordingtotheinvestigationonfatigueexperimentandobservedresults,therearetwokindsoffatiguelimitexistonM/Wwithinfatiguefracturelife(Nf=106~107cycles),oneisfatiguecracksinitializingonthetopsurfaceofM/Wcalledsurfacefatiguelimit(wsσ)andanotherisfatiguecracksinitializingonthesub-surfaceofM/Wcalledinternalfatiguelimit(wiσ)[1].
(3)Basedonthedislocationtheory,therelationshipbetweenwsσandwiσcanbeobtainedinthesamekindengineeringmaterialafterheattreatment[1].
40.
1~35.
1=wswiσσ(1)Eq.
(1)illustratesthatifhighcompressiveresidualstressesareintroducedinthetopsurface,thefatigueheadstreamcanbesuppressedinsub-surface,andthefatiguelimitofhighfatiguelife(Nf=106~107cycles)canbeimproved35%~40%.
3.
2ThecalculationofoptimizedcompressiveresidualstressfieldinM/WsurfaceintroducedbySP[2]Basedon"microprocesstheoryoffatiguecrackinitiation"and"internalfatiguelimittheory",inordertoimprovethefatiguelimitofhighfatiguelife(Nf=106~107cycles)fromwsσ(Surfacefatiguelimit)towiσ(Internalfatiguelimit),twocriterionsaboutobtainingoptimizedcompressiveresidualstressfieldhavebeenproposed.
CriterionA:Therelationshipbetweenwiσandintroducedcompressiveresidualstressesofsurfacersσhasbeenshowninformula(2).
wiσ-rsσtσ/wiσ>0.
96Fromformula(3),itrevealsthatonlytσincreasesandreachesthevalueofwiσatZs,thefatigueheadstreamisabletogerminateandcausefatiguefractureunderhigherstresses(wiσ).
Basedonabovediscussionabouttwocriterions,itcanbefoundthatonlyfulfillabovetwocriterions,theintroducedresidualstressfieldbySPwillbeoptimizedstressfieldandtheeffectofpeeningwillreachesthebest.
Thiseffectofresidualstressstrengtheningisnamedindirectstrengtheningmechanismofresidualstress.
3.
3EstablishthecompositestrengtheningtheoriesofSP(1)Residualstressindirectstrengtheningmechanismhasbeendiscussedin3.
2.
(2)ResidualstressdirectstrengtheningmechanismAsthefatiguelimitofmiddlefatiguelife(Nf=105~106cycles),thePTandintroducedcompressiveresidualstressesshouldfulfiltherequirementsasfollows.
(a)AvoidtheincreaseofstressconcentrationfactorKtresultedfromtheincreaseofsurfaceroughnessRa.
(b)ImprovetheresidualstressofsurfacersσofM/WbychoosinganappropriatePT,suchasMulti-SP,prestressingSP,warmSPetal.
(c)Improvetheresidualstressofsurfaceinordertoimprovefatiguecrackgerminationlife(Ni)andreducetheexpandingvelocity(da/dN)offatiguecrackinresidualstressfield.
(3)MicrostructuralstrengtheningmechanismTherearethreekindsoffracturemodels(FM)ofM/Wwhenenduringalternatingtwistloading,normaltensilefracturemodel(NTFM),longitudinalshearfracturemodel(LSFM),andtransverseshearfracturemodel(TSFM).
Thefatiguefracturelife(Nf)iscontrolledbyFM.
Theexperimentsoftwistfatigue[3]revealthatwiththeincreaseoftensileyieldstrength(0.
2σ)andtwistyieldstrength(0.
3τ),thesequenceofthelengthofNfwithdifferentFMisshownasNTFMLSFM>TSFM.
Consequently,thevariationofstructureresultsinthechangeofFMandtheimprovementofNf,whichisthemicrostructuralstrengtheningmechanism.
Insummary,theexperimentalinvestigationsonPTandthefieldofappliedfoundationinChinacanbeconcludedinFig.
3.
TheaimofSPisthatonthebaseofconsideringthecompositepropertiesofM/Wtotreateachworkpiece.
Ofcourse,nometterinthedegreeofdepthandinthescope,itisnotasgoodasthedevelopedcountriesontheapplicationofshotpeeningtechnologiesinthefieldofmanufacturesinChina.
WewillworkhardtodevelopthepracticalapplicationofPTinthedifferentfieldsofmanufacturesinChina.
Fig.
3CompositestrengthenmechanismofSPReferences[1]WangRenzhi,YaoMei,etal.
AMicro-meso-ProcessTheroyofFatigueCrackInitiationandTheroyofInternalFatigueLimit,Trans.
ofMetalHeatTreatm.
,Vol.
16(4)(1995)pp26-33.
[2]WangRenzhi,YaoMei.
TheEngineeringCalculationMethodoftheOptimumResidualStressFieldIntroducedbyShotPeeningintotheSurfaceLayerofSpring,Trans.
ofMeterialsandHeatTreatm.
,Vol.
24(4)(2003)pp3-7.
[3]Z.
Hu,L.
MaandS.
Gao.
AStudyofShearFatigueCrackMechanisms.
FatigueFract.
Engng.
Mater.
Struct.
,Vol.
15(6)(1992),pp563-572.
[4]WangRenzhi,JiangChuanhai.
NormalandShearFatigueFractureModelofCircularCoilSpringandtheWayforImprovementofItsFatigueFractureResistance.
Proceedingsof11thInternationalConferenceonShotPeening,(2011)ImproveshearstressfatiguestrengthM/WResidualstressdirectstrengtheningmechanismResidualstressindirectstrengtheningmechanismImproveσ0.
2andτ0.
3ofsurfaceImproveHv,σ0.
2andτ0.
3ofsurfaceCycleplasticstrainhardeningandstructuralstrengtheningmechanismCompressiveresidualstressstrengtheningmechanismReduceStressconcentrationfactorKtaccordingtoreducetheroughnessofsurfaceDeformationstrengtheningmechanismofSPonsurfaceImprovecompressivestressfatiguestrengthofM/W
ThispapergivesabriefintroductionofdevelopmentofshotpeeningindustryinChina,whichincludesshotpeeningequipmentandpeeningmediamanufacturing,processplanningaboutshotpeeningandapplicationfieldsofdifferenttypesofshotpeening.
Intermsofbasicresearchofshotpeening,thispapersummarizessomenotableresearchresultsaboutstressstrengtheningandmicrostructurestrengtheningofshotpeening,influenceofshotpeeningonfatiguelifeofspecificmaterial,resistancetosomeformsofstresscorrosionandsoon.
Furthermore,applicationofconventionalshotpeeningtreatmentonadvancedmaterials,newshotpeeningtechniqueandcomputermodelingtechniqueaboutshotpeeningprocessalsodevelopveryrapidlyinChina.
Keywords:Shotpeening,Development,ChinaIntroductionPeeningmachine(PM),peeningshot(PS)andpeeningtechnologies(PT)arethreeveryimportantfactorsofshotpeening(SP)treatmenttechnologiesforworkpieces.
TherelationshipbetweenthesethreefactorshasbeenshowninFig.
1.
Fig.
1.
ThreefactorsofSPtreatmenttechnologiesforworkpiecesandtherelationshipwitheachother.
PS/PTPM/PS/PTPMPSPM/PSPM/PTPTSPtreatmenttechnologiesworkjustlikeamedicine,whichcantreatandimprovethefatiguefractureresistance(FFR)andstresscorrosioncrackingresistance(SCCR)ofmechanicalworkpieces.
Inordertoobtaintheoptimumstrengtheningeffect,thePMandPSmustfulfillalltherequirementsofPTdecidedbyworkpieces,suchaslocationsofSP,SPintensities,coverageofsurface,roughnessofSPandsoon.
AfterSP,thestructuresofsurfacelayersofworkpiecesarechangedasfollows:circulatingstrainhardeningofsurfacestructureandintroducedcompressiveresidualstress,whichcanimproveFFRandSCCRofmaterials/workpiece(M/W)accordingtostructurehardeningmechanismandresidualstresshardeningmechanismrespectively,besides,circulatingstrainrelaxationofsurfacestructureandincrementofsurfaceroughnesscanreduceFFRandSCCRofM/Wtoacertainextent.
ThevariationshavebeenshowninFig.
2.
TheSPtreatmentsofM/WshoulddependonfinePMandPStoobtaincompositestrengtheningeffectsofthevariationsmentionedinFig.
2tothemostdegree.
Fig.
2.
ThechangesofworkpiecesinsurfacelayersafterSPAccordingtothethreefactorsmentionedinFig.
1,combinethedevelopmentofSPinChinaandeachfactorwillbepresentedasfollows.
1.
ThedevelopmentofPMmanufacturePMismainlyusedtomodifyandimproveFFRandSCCRofM/W.
AndmanufacturecompaniesdesignandfabricatePMaccordingtofollowbasicprinciples.
(1)Basedonthematerials,shape,size,peeninglocation,etaltodesignthePM.
(2)Basedontherisklocationstendedtofatiguefracture,andspecialSPparameters(SPintensities,surfacecoverage,shottype,sizeandhardness)todesignthePM.
(3)InordertoimprovethestabilityandrepeatofSPparameters,theshotdiameterfilter,thecrackedshotsegregator,themonitorofshotvelocityandflux,andotheraccessoriesshouldbefixedinPM.
ChangesofsurfaceroughnessIncreaseofsurfacestressconcentratecoefficientKtDecreaseofsurfacestressconcentratecoefficientKtIntroduceresidualstressinsurfacelayersTensileresidualstressindeepsurfaceCompressiveresidualstressintopsurfaceDynamiccirculatingstrainhardeningofstructureDynamiccirculatingstrainintenerateofstructureVariationsofsurfacelayerofM/WafterSP(4)Accordingtotheoutput,geometricshape,size,andeconomicbenefitofworkpieces,considerwhichtypePMwillbechose,airblasttypePMormechanicaltypePM.
Basedonaboveprinciples,manytypesofPMhavebeenmanufacturedinlatest20years.
Somerepresentativetypeshavebeendisplayedasfollows.
(1)SpecialairblasttypePMdesignedforSPonaircraftengines,turbinediscandturbineblade.
(2)SpecialairblasttypePMdesignedforSPonlandinggearworkpieces.
(3)SpecialPMdesignedforSPoninner-hollow(Φ120mm)longaxes(1700mm).
(4)SpecialmechanicaltypePMdesignedforSPonlongsuckers(8m)usedinoilwell.
(5)SpecialPMdesignedforSPonsuspensionspring,valvespringandtunnelworkpieces.
(6)Specialcomputerizednumericalcontrol(CNC)airblasttypePMdesignedforSPongasturbinebigblade.
(7)AirblasttypeandmechanicaltypePMdesignedforSPonsomekindsofgears.
Recently,thecombiningresearchesbyShanghaiCarthingMachinaryCo.
,Ltd(Shanghai,China)andShanghaiJiaoTongUniversity(Shanghai,China)makefive-shaftdiveCNCairblasttypePMmanufactured,andwhichmakesthehighaccurateCNCPMhomebredfirstly.
Afterthat,ShanghaiCarthingMachinaryCo.
,LtdhasmanufacturedtherobotcontrolledCNCPM,usingtherobotsonPMsuccessfully.
Andnow,SomeCNCPMsmadeinChinahavebeenexportedtoIndia,Turkeyandothercountries.
Certainly,itisjusttheinitialdevelopmentofCNCPMinChina,andthereisabiggapbetweendevelopedcountries.
Wewillhavealongwaytogocomparedwithforeigndevelopments.
2.
ThedevelopmentofPSmanufactureIn1950's,afewdepartmentsofindustry(eg.
aerialindustry)hadstartedusingPT.
Early,thematerialofPSwascaststeel,thentheglassbeadswereintroducedasshotmediaforaircraftenginesworkpieces.
ThepeeningcaststeelshotsaccordedwithSAEJ444astylehadbeenmanufacturedin1970'sinChina.
ShandongKaiTaiIndustrialTechnologiesCo.
,LtdisthebiggestcompanyinChina,andthefourthbiggestcompanyintheword.
Intherecentdecade,withthefastdevelopmentofautomobileindustry,thedemandsofcuttingsteelshotsbecomemoreandmorein-country.
SomecompanieslikeJiangsuDaQiGroupCo.
,Ltd.
astheheadcanmanufacturethousandstonsofcuttingsteelshotseachyearwhichareconsistentwiththestandardofSAEJ441,AMS2431,MIL-S-13165C,VDFI8001andDIN8201.
Thesecuttingsteelshotscanbefulfillednotonlythedemandofin-countrycompanies,butalsoexportedtothemarketofEurope.
3.
ThedevelopmentofPTmanufactureIn1960's,theinfluenceofSPonthefatigueandfracturepropertiesatelevatedtemperatureofNi-basedhightemperaturealloyshavebeeninvestigatinginsystem,andthePThadbeenusedonturbinebladeandaircraftenginessuccessfullyaccordingtoaboveinvestigations.
Theinvestigationscanreducetroublesofturbinebladeandprolongtheuselifeindouble.
Theindustrystandardof"TheIllustrationofShotPeeningTechnologiesofAircraftWorkpieces"(HB/Z26-92)designedbyaircraftmanufactureisthefirstaeronauticalandspaceflightindustrystandardofP.
R.
China.
Inrecent40years,theexperimentalstudyofappliedfundamentaltheoryofPThasbeenshowninfollowthreefacets.
3.
1Theexperimentalstudyoffatigueandfractureofmetalengineeringmaterials(1)Accordingtotheinvestigationonfatiguecrackinitiationofengineeringmaterials,microprocesstheoryoffatiguecrackinitiationhasbeenproposed[1].
(2)Accordingtotheinvestigationonfatigueexperimentandobservedresults,therearetwokindsoffatiguelimitexistonM/Wwithinfatiguefracturelife(Nf=106~107cycles),oneisfatiguecracksinitializingonthetopsurfaceofM/Wcalledsurfacefatiguelimit(wsσ)andanotherisfatiguecracksinitializingonthesub-surfaceofM/Wcalledinternalfatiguelimit(wiσ)[1].
(3)Basedonthedislocationtheory,therelationshipbetweenwsσandwiσcanbeobtainedinthesamekindengineeringmaterialafterheattreatment[1].
40.
1~35.
1=wswiσσ(1)Eq.
(1)illustratesthatifhighcompressiveresidualstressesareintroducedinthetopsurface,thefatigueheadstreamcanbesuppressedinsub-surface,andthefatiguelimitofhighfatiguelife(Nf=106~107cycles)canbeimproved35%~40%.
3.
2ThecalculationofoptimizedcompressiveresidualstressfieldinM/WsurfaceintroducedbySP[2]Basedon"microprocesstheoryoffatiguecrackinitiation"and"internalfatiguelimittheory",inordertoimprovethefatiguelimitofhighfatiguelife(Nf=106~107cycles)fromwsσ(Surfacefatiguelimit)towiσ(Internalfatiguelimit),twocriterionsaboutobtainingoptimizedcompressiveresidualstressfieldhavebeenproposed.
CriterionA:Therelationshipbetweenwiσandintroducedcompressiveresidualstressesofsurfacersσhasbeenshowninformula(2).
wiσ-rsσtσ/wiσ>0.
96Fromformula(3),itrevealsthatonlytσincreasesandreachesthevalueofwiσatZs,thefatigueheadstreamisabletogerminateandcausefatiguefractureunderhigherstresses(wiσ).
Basedonabovediscussionabouttwocriterions,itcanbefoundthatonlyfulfillabovetwocriterions,theintroducedresidualstressfieldbySPwillbeoptimizedstressfieldandtheeffectofpeeningwillreachesthebest.
Thiseffectofresidualstressstrengtheningisnamedindirectstrengtheningmechanismofresidualstress.
3.
3EstablishthecompositestrengtheningtheoriesofSP(1)Residualstressindirectstrengtheningmechanismhasbeendiscussedin3.
2.
(2)ResidualstressdirectstrengtheningmechanismAsthefatiguelimitofmiddlefatiguelife(Nf=105~106cycles),thePTandintroducedcompressiveresidualstressesshouldfulfiltherequirementsasfollows.
(a)AvoidtheincreaseofstressconcentrationfactorKtresultedfromtheincreaseofsurfaceroughnessRa.
(b)ImprovetheresidualstressofsurfacersσofM/WbychoosinganappropriatePT,suchasMulti-SP,prestressingSP,warmSPetal.
(c)Improvetheresidualstressofsurfaceinordertoimprovefatiguecrackgerminationlife(Ni)andreducetheexpandingvelocity(da/dN)offatiguecrackinresidualstressfield.
(3)MicrostructuralstrengtheningmechanismTherearethreekindsoffracturemodels(FM)ofM/Wwhenenduringalternatingtwistloading,normaltensilefracturemodel(NTFM),longitudinalshearfracturemodel(LSFM),andtransverseshearfracturemodel(TSFM).
Thefatiguefracturelife(Nf)iscontrolledbyFM.
Theexperimentsoftwistfatigue[3]revealthatwiththeincreaseoftensileyieldstrength(0.
2σ)andtwistyieldstrength(0.
3τ),thesequenceofthelengthofNfwithdifferentFMisshownasNTFMLSFM>TSFM.
Consequently,thevariationofstructureresultsinthechangeofFMandtheimprovementofNf,whichisthemicrostructuralstrengtheningmechanism.
Insummary,theexperimentalinvestigationsonPTandthefieldofappliedfoundationinChinacanbeconcludedinFig.
3.
TheaimofSPisthatonthebaseofconsideringthecompositepropertiesofM/Wtotreateachworkpiece.
Ofcourse,nometterinthedegreeofdepthandinthescope,itisnotasgoodasthedevelopedcountriesontheapplicationofshotpeeningtechnologiesinthefieldofmanufacturesinChina.
WewillworkhardtodevelopthepracticalapplicationofPTinthedifferentfieldsofmanufacturesinChina.
Fig.
3CompositestrengthenmechanismofSPReferences[1]WangRenzhi,YaoMei,etal.
AMicro-meso-ProcessTheroyofFatigueCrackInitiationandTheroyofInternalFatigueLimit,Trans.
ofMetalHeatTreatm.
,Vol.
16(4)(1995)pp26-33.
[2]WangRenzhi,YaoMei.
TheEngineeringCalculationMethodoftheOptimumResidualStressFieldIntroducedbyShotPeeningintotheSurfaceLayerofSpring,Trans.
ofMeterialsandHeatTreatm.
,Vol.
24(4)(2003)pp3-7.
[3]Z.
Hu,L.
MaandS.
Gao.
AStudyofShearFatigueCrackMechanisms.
FatigueFract.
Engng.
Mater.
Struct.
,Vol.
15(6)(1992),pp563-572.
[4]WangRenzhi,JiangChuanhai.
NormalandShearFatigueFractureModelofCircularCoilSpringandtheWayforImprovementofItsFatigueFractureResistance.
Proceedingsof11thInternationalConferenceonShotPeening,(2011)ImproveshearstressfatiguestrengthM/WResidualstressdirectstrengtheningmechanismResidualstressindirectstrengtheningmechanismImproveσ0.
2andτ0.
3ofsurfaceImproveHv,σ0.
2andτ0.
3ofsurfaceCycleplasticstrainhardeningandstructuralstrengtheningmechanismCompressiveresidualstressstrengtheningmechanismReduceStressconcentrationfactorKtaccordingtoreducetheroughnessofsurfaceDeformationstrengtheningmechanismofSPonsurfaceImprovecompressivestressfatiguestrengthofM/W
UCloud年度大促活动可选香港云服务器低至年134元
由于行业需求和自媒体的倾向问题，对于我们个人站长建站的方向还是有一些需要改变的。传统的个人网站建站内容方向可能会因为自媒体的分流导致个人网站很多行业不再成为流量的主导。于是我们很多个人网站都在想办法进行重新更换行业，包括前几天也有和网友在考虑是不是换个其他行业做做。这不有重新注册域名重新更换。鉴于快速上手的考虑还是采用香港服务器，这不腾讯云和阿里云早已不是新账户，考虑到新注册UCLOUD账户还算比...
香港CN2云服务器 1核 2G 35元/月 妮妮云
妮妮云的来历妮妮云是 789 陈总 张总 三方共同投资建立的网站 本着“良心 便宜 稳定”的初衷 为小白用户避免被坑妮妮云的市场定位妮妮云主要代理市场稳定速度的云服务器产品，避免新手购买云服务器的时候众多商家不知道如何选择，妮妮云就帮你选择好了产品，无需承担购买风险，不用担心出现被跑路 被诈骗的情况。妮妮云的售后保证妮妮云退款 通过于合作商的友好协商，云服务器提供2天内全额退款到网站余额，超过2天...
DiyVM（50元起）老牌商家,香港沙田CN2直连vps/不限流量/五折终身优惠
diyvm怎么样?diyvm是一家国内成立时间比较久的主机商家了，大约在6年前站长曾经用过他家的美国机房的套餐，非常稳定，适合做站，目前商家正在针对香港沙田机房的VPS进行促销，给的是五折优惠，续费同价，香港沙田机房走的是CN2直连的线路，到大陆地区的速度非常好，DiyVM商家采用小带宽不限流量的形式，带宽2Mbps起步，做站完全够用，有需要的朋友可以入手。diyvm优惠码：五折优惠码：OFF50...
大旗网论坛为你推荐
-
快递打印怎么在电脑上打印快递单yy频道中心yy频道怎么进频道中心，求图~！拂晓雅阁有什么网站是学电脑技术的`?微信如何建群微信怎么建群？伪静态如何设置伪静态规则arm开发板开发板是什么？如ARM开发板，DSP开发板等。。它和最终目标板有何区别？申请证书一、如何申请证书？天天酷跑刷金币天天酷跑如何刷分刷金币？godaddy通过什么网址可以查godaddy的域名信息bt封杀北京禁用BT下载，是真的吗？为什么？