H13热作模具钢疲劳蠕变交互损伤模型.pdf 10页

'中国科技论文在线http://www.paper.edu.cnStudyonthefatigue-creepinteractiondamagemodelfor#H13*LuoYuanxin,DuWeiqi5(ChongqqingUniversity,CollegeofMechanicalEngerneering,Chongqing,400000)Abstract:AISIH13(4Cr5MoSiV1)asmainmaterialofextrusiontoolsuffersfromfatigueandcreepdamageduetoitsextremeworkingcondition.Stress-controlledfatigueandcreep–fatigueinteractionexperimentshavebeencarriedoutat500°Ctoinvestigateitsdamageevolution.Anewfatigue-creepinteractiondamagemodelhasbeenproposedonthebasisofcontinuedamagemechanics(CDM).A10newequivalentimpulsedensityforfatigue-creeptestswasproposedtobytransformingcreepimpulsedensityintofatigueimpulsedensity.Theexperimentalresultsindicatedthatthedamagemodelcanbemoreapplicabletodescribethedamageevolutionforcreep–fatigueinteraction.Keywords:metalmaterial;fatigue-creep;continuedamagemechanics(CDM)150IntroductionExtrusioniswellknownasahigh-volumeproductionprocesstoproducealuminumpartswithfixedsectionalprofilesforapplicationsintheindustriesofconstruction,automobile,aerospace,etc.It’sreportedthattherepairandreplacementofextrusiontoolshassignificantimpactontheproductioncostsduetothefailurecausedbythethermo-mechanicalloadingof20extrusion.Inatypicalindustrialsetting,uptohundredsofbilletswillbeextrudedsequentiallyatafrequencyof10billetseveryhour,whichleadstorepetitiveloadingandunloadingexertedon[1]extrusiontools.Intheextrusionprocess,thebilletforcedtoflowthroughthetoolsleadstoaformingload,whichcanbeconsideredstableoverasinglestroke(dwelltime).Moreover,athermalbalanceofthedie-presssystemwillbegenerallyobtainedafteraninitialwarm-upphase25oftheprocess(around3-5ramstrokes),keepingthedietemperatureremainingfairlystableduring[2]extrusion(450°Cto500°C).Theextrusiondieisunderthefatigue-creepinteractionduetothecombinedeffectofstableformingloadathightemperatureinmultiplebilletsproduction,whichplaysakeyroleinthefailuremechanisms.Thefamilyof5%chromiumhot-worktoolsteelse.g.,AISIH11(X38CrMoV5-1),AISIH1330(4Cr5MoSiV1),arecommonlyusedthematerialofaluminumextrusiontools.Toprolongthelifetimeofextrusiondies,someeffortsweremadeimprovethehightemperaturepropertiesof[3]thesehottoolsteelsbymodificationofcomposition.Delagnesetal.studiedtheinfluenceofsiliconcontentonfatiguepropertiesofa5%Crtemperedmartensiticsteel.TheyfoundthemodifiedAISIH11toolsteel(0.35wt.%silicon)exhibitsimprovedtensileandfatigueproperties35at550°Cthanthoseofconventionalones(approximately1wt.%silicon).SomeresearcherstriedthenewtechniqueoflasersurfaceremeltingtoimprovethehightemperaturepropertiesofAISI[4]H13.Theyfoundthatthehardnessofhottoolsteelsurfacewasimprovedandbetterfatigue[5]resistancewasfoundcomparedtotheuntreatedone.Otherswerefocusedonthefailure[6]mechanismsofhottoolsteelunderitsextremelyworkingcondition.Kchaouetal.investigated40thehotforgingfailuremechanismofAISIH13diesandfoundthatplasticdeformationandfatigue[7]areusuallyquotedasthemaindamage.Reggianistudiedthehigh-temperaturebehaviorofAISIH11temperedsteelinordertodeterminetherolethatcreepandfatigueplaysinthealuminumextrusionprocess.Fatiguecrackpropagationwasalsopaidmuchattentiontobothatroomandelevatedtemperature.However,thenonlinearfatigue-creepinteractionofhottoolsteelwaslackedFoundations:DoctoralProgramofHigherEducationofChina(No.20130191120004)Briefauthorintroduction:LuoYuanxin(1981-),male,AssociatedProfessor,Researchfield:Metalformingprocess.E-mail:yxluo@cqu.edu.cn-1- 中国科技论文在线http://www.paper.edu.cn45enoughconcernsandfewstudieswerefocusedonitsfatigue-creepdamageevolution.Inpresentstudy,creep-fatigueinteractiondamageevolutionoftheAISIH13steelisinvestigatedandacreep-fatiguedamagemodelhasbeenidentifiedbystresscontrolledcreep-fatigueinteractiontestoftheAISIH13steel.Anovelequivalentfatigueimpulsedensitywasproposedtobytransformingcreepimpulsedensityintofatigueimpulsedensity.Tostudyits50properties,fatigueandfatigue-creeptestsofAISIH13wereperformedat500°C,whichisclosedtoworkingcondition.Theaccumulatedplasticstrainisselectedtodefinethedamagevariableduetoitsclearphysicalmeaning.Damageexponentisusedtodescribethematerialdamagelevelandtheeffectsofmechanicalloadandholdtime.1CDMtheoreticalmodelforcreep–fatigueinteraction55ContinueDamageMechanics(CDM)canbeconsideredasaneffectivemethodtoinvestigatefatiguedamageevolution.Itdescribesthatthedamageoffatiguemainlycausedbytheaccumulatedplasticstraincanbedescribedbyanappropriateequationofdissipationpotential.KrajcinovicandLemaitrehaveproposedthedescriptionofdamageevolutioninthethermo-dynamicalterms.TheLCFdamagefunctioncanbeexpressedasfollows:Df60Y(1)whereisdissipatepotentialandYisdamagestrainenergyreleaserate.Therehavebeen[8]variousdissipationpotentialuntilnow.Yangetal.proposedthedamagepotentialfunctionEq.(2),whichcanbesufficienttodescribethemainpropertieswithinthehypothesisofisotropydamage.2Yp2(SD1)0650(2)wherepistheaccumulatedplasticstrainandS0istemperaturedependedmaterialconstantwhichcanbeevaluatedfromthelawofMason-Coffin.0isamaterialconstantrelatedtothetemperature,loadinglevels,materialproperties,etc.,whichcandescribetheextentofaccumulateddamage.Also,Yangetal.considereditmoreappropriatetoreflecttheinfluenceofaccumulated70plasticstrainbyreplacing(1-D)with(1-N/Nf).Thustheequationcanbeexpressedas:2Yp02S01/NNf(3)SubstitutingEq.(3)intoEq.(1),theobtainedisothermalLCFdamagefunctionisshownas:YpDfSNN001/f(4)DDD1NN0NNfForboundarycondition,0and,thedamageevolutionforLCFcanbe75expressedas:DD1(1)(1N/)N10ff0(5)1Intheaboveexpression,thedamageexponent0canbeconsideredasafunctionofstressforisothermalLCF,inwhichthedamagerateisonlydependentontheloadinglevels.Many[9]studiesshowthatthelifetimeissignificantlyrelatedtothestressamplituderecognizedasthe80mostimportantparameterforstress-controlledfatigue.Meanwhile,Itisfoundthattheprogressiveaccumulationofplasticdeformationinducedbytensilemeanstresshasimpactonfatiguelifeof[10][11][12]variousmaterialssuchas42CrMoSteel,Zircaloy-2,45Steel.Therefore,therearemany-2- 中国科技论文在线http://www.paper.edu.cnmodel,suchasGoodman,Smith–Watson–Topper(SWT),etc.,thatformulatestheequivalentstresswiththeparameterofstressamplitudeandmeanstress.85Increep–fatiguetests,atensiledwelltimeisintroducedandthedamagemechanismshouldbeconsideredastimedependentdamagefactortoaccuratelyreflectthematerialbehavior.Thelineardamagesummationmethodwasproposedwithoutconsiderationoftheinteractionbetweenfatiguedamageandcreepdamage,thatis:DDDtfc(5)90where,Dt,DfandDcarerepresentedthetotaldamage,creepdamageandfatiguedamage,respectively.TofurtherunderstandthefailuremechanismofH13undertheworkingconditionofaluminum,the,thefracturesurfacesofcreepandfatigue-creepspecimens(withdwelltimeof0s,10s,600s)wereobservedbyScanningelectronmicroscope(SEM).Figure1ashowsthefracture95surfaceonthecreepspecimenthatiswithintergranularbrittlefracture.Thefailuremechanismisprobablycausedbystrainlocalizationandcreepcavitationformingatgrainboundaries.Itdeterioratesthestrengthofgrainboundariesandmakesitbrittle,finallyleadstolocalgrain-boundaryseparationwithvoidthenucleationandpropagation.Figure2b,canddshowfracturesurfacesofspecimenwithholdingtimeof0s,10s,600s.Thefatiguestriationscanbe100moreclearlyobservedwithholdingtimeof600sthanthatof0s,10s.Moresecondarycracksarealsofoundwiththeincreaseofholdingtime.Thephenomenoncanbeexplainedbyinteractionofthedamageeffectoffatigueandcreep.Fig.1FracturemicrographsofAISIH13withdifferentholdtime(a)creep(b)0s(c)10s(d)600s105Someeffortsaremadetofigureoutthestress-controlledfatigue-creepinteractiondamage[13]model.Zhangetalproposedageneralcreep–fatigueinteractionaccumulationlawbycouplingthedamageexponentoffatigueandcreepintoauniformformat.However,stressamplitudewasonlyconsideredinthedamageexponentfunctionforsimplification.Fanetaltookmeanstresseffectintoconsiderationandexpressedthedamageexponentasafunctionof110maximumstressandstressamplitude.Tomorepreciselydescribethedamageexponent,an-3- 中国科技论文在线http://www.paper.edu.cnadditionaltimedependentvariableshouldbeintroduced.However,anaddingvariablemakesthedamageexponentbecomeamultivariatefunctionanditisrelativelydifficulttoexplorethespecificfunctionequation.Hence,it’snecessarytosearchforanovelparametertocombinetheeffectofstressandholdtimesimilartotheequivalentstressinfatigueprocess.115Variousinevitablymicrodefectswillbegeneratedinthespecimenunderfatigue-creepload(e.g.dislocation,void,microcrack,etc.).Theseirreversibleprocessesoccurwiththeincreaseofinternalenergy.Alocalformcanbederivedfromthelawofenergyconservationforthespecimenunderhightemperaturefatigue-creeptests:dedQdtdt(6)120whereeistheinternalenergypermass,Qisthethermalenergy.Eq.(6)indicatesthattheinternalenergyaccumulationequalstothechangeofthemechanicalworkandheattransfer.Forisothermaltests,thecomplicatedheatexchangeisrelatedtothemechanicalworktokeepthetemperatureofspecimenconstant.Andthus,therightsideofEq.(6)canbegivenasafunctionofmechanicalwork:def125dt(7)Sincedamagegenerateswiththechangeofinternalenergyandinternalenergyisimmeasurable,thefunctionofappliedworkdonecanbedefinedasaparametertodescribe[14]materialdamage.Zhu.et.alproposedanovelviscosity-basedparameterusingstress-timediagramtopredictlowcyclefatigue-creeplife.Thelifepredictedmodelcanbewidelyapplicable[15]130andshowedgoodagreementwithreportedexperimentaldatafromliterature.Jiet.alconsideredthatthecompressionholdingperiodisalsodeleterioustomaterialanddevelopedafatigue-creepElifetimemodelbasedonappliedmechanicalworkdensity.Thetestimpulsedensitywwasintroducedtodescribeappliedmechanicalworkpercycle,asshowninFigure2.Itseemsmoreappropriatetobeconsideredasacouplingparameterofstressandholdtime.Therefore,the135damageexponentcouldbeexpressedasaunivariatefunctionasfollows:10fEw(8)22maxminT0ETwhmax0maxminminmaxminT0ETwhmax02min-4- 中国科技论文在线http://www.paper.edu.cn140Fig.2Stress-timediagramofthestress-controlledcreep-fatiguetestHowever,itcanbefoundinFigure1thatthemicrostructuraldamagemechanismofcreepisrelativelydifferentfromthatoffatigue.Morespecifically,creepcavitationevolutioncausesthestrainlocalizationneargrainboundariesandleadstothevoidnucleationandpropagation,whilefatiguecyclicintrusionandextrusionleadstothecrackinitiationandpropagationatthematerial[16]145surface.Therefore,thecreepcounterpartandfatiguecounterpartinimpulsedensityshouldcomplywithdifferentenergy-damagerelationships.Therefore,theappliedworkdoneshouldbedividedintotwoparts,holdtimeperiodandtheremainingrampperiod,respectively.2ExperimentalDetails2.1Material150ThematerialinvestigatedinthepresentstudyisAISIH13andthecylindricalspecimensweretakenoutofaforgedingot,ofwhichthechemicalcompositionispresentedinTable1.Toachievethehardnessof47-49HRC(Rockwellhardness),heattreatmentincludesaustenitisingat1020°Cfor1hourfollowedbynitrogenquenching,towtemperingtwiceat570℃and550℃,respectively,andthenaircoolingtoroomtemperature.Figure3showsthedifferentmagnification155ofmicrographofAISIH13afterheattreatmentwithOM(OlympusMeasuringLaserMicroscopeOLS4000)andJEOLJSM-7800FfieldemissiongunScanningElectronMicroscope(SEM).ItcanberevealedthatthehardenedandtemperedAISIH13toolsteeliswithlargequantitiesoffinetemperedmartensitelath.-5- 中国科技论文在线http://www.paper.edu.cn160Fig.3DifferentmagnitudemicrographofAISIH13afterheattreatmentTable1Chemicalcompositionofhot-worksteelAISIH13ElementCSiMnCrMoVWeight-%0.40.970.35.371.341.22Thestress-straincurveofAISIH13hottoolsteelat500°CisshowninFigure4.Thehightensilestrengthcanbefoundat500°Cafterheattreatment.ThreetensiletestswereconductedtoacquiretheaveragevalueofthetensilepropertiesofAISIH13steel.165Fig.4Stress-straintensilecurveofAISIH13steelat500°C3ResultsFigure5showsexperimentresultsofthefatiguedamageevolutionofAISIH13hottoolsteel.Figure6showstheexperimentresultsof-500-1500MPainstress-controlledtestswithdifferent-6- 中国科技论文在线http://www.paper.edu.cn170holdtime(0s,10s,30s,60s,180s,600s).Table2givesthedetailedimpulsedensity(creepperiodandfatiguepart),damageexponentforbothoffatigueandfatigue-creep.Fig.5FatiguedamageevolutionofAISIH13hottoolsteelundervariousload175Fig.6Damageevolutionof-500-1500MPainstress-controlledtestswithdifferentholdtimeTable2DetailsofimpulsedensityanddamageexponentNo.HoldingImpulsedensityImpulsedensityDamagetime(s)(fatiguepart)(creeppart)exponent(MPa)33(10MPas)(10MPas)1-300130001.7800.6062-400-140002.1200.3643-500-150002.5000.1574-600-160002.9200.1045-800-160003.2000.0896-1000-160003.5600.0967-500-1500102.5015.00.1408-500-1500302.5045.00.124-7- 中国科技论文在线http://www.paper.edu.cn9-500-1500602.5090.00.11810-500-15001802.502700.09211-500-15006002.509000.088FromTable2,itcanbefoundthatdamageexponentdecreasewiththeincreaseoftheimpulsedensity.Thismeansthatthehighexternalworkwillleadtodrasticallyinternaldamage.180Also,theimpulsedensitycorrespondingtofatigueisrelativelysmallerthanthatofcreepanditrevealsthatthematerialismoresensitivetoimpulsedensityoffatiguepart.Figure7showstherelationshipbetweenthedamageexponentandimpulsedensityinfatiguetests.Thefunctionoffatiguedamageexponentcanbeobtainedasfollows:3.3514.97eE10(9)0fE185wherefisthefatigueimpulsedensity.Fig.7RelationshipbetweendamageexponentandimpulsedensityinfatiguetestsRegardlessofwhatloadformitis,materialdamagelevelcanbedescribedbythedamageexponent.Thisindicatesthatthedamageexponentoffatigue-creeptestscanbesubstitutedinto190Eq.8.Thecalculatedresultscanbedefinedastheequivalentimpulsedensity.Thensubtracttheimpulsedensityoffatiguepart,theremainingistheequivalentfatigueimpulsedensitytransformedformthecreeppart.Table3showsthedetailsofequivalentimpulsedensityoffatiguecorrespondingtothatofcreepperiod.Figure8showsdetailedfittingcurvesofequivalentfatigueimpulsedensityandcreepimpulsedensity.Therefore,thedamageevolutionfunctionofAISIH13195at500°Ccanbeobtainedasfollows:3.35eqN4.9710eEfDD1(1)(1)(10)N0Nf22eqmaxminT00.208ETfh41.6maxmin0maxmin-8- 中国科技论文在线http://www.paper.edu.cneqmaxminT00.208ETfh41.6maxmin02Table3DetailsofequivalentfatigueimpulsedensityandcreepimpulsedensityNo.DamageEquivalentfatigueimpulseCreepimpulsedensityexponentdensity(102MPas)(104MPas)70.1402.921.5080.1243.954.5090.1184.389.00100.0926.0427.0110.0887.0790.0200Fig.8Fittingcurvesofequivalentfatigueimpulsedensityandcreepimpulsedensity4ConclusionInpresentstudy,fatigueandcreep–fatigueinteractionexperimentshavebeencarriedoutforAISIH13hottoolsteelunderstresscontrolmodewithatrapeziumwaveform.SEMobservation205offracturemicrographsshowsdifferentmicrostructuraldamagemechanismofcreepandfatigue,creepdamagedeterioratesthegrainboundaryandfatiguestriationsareclearerwithmoresecondarycrackswiththeincreaseoftheholdtime.AcontinuumdamageevolutionmodelofisotropicfatigueisderivedonthebasisofCDMtheory.Theaccumulatedplasticstrainperfatigue-creepcyclecanbeusedtodescribethenonlinearinteractionoffatigue-creepdamage.210Impulsedensitywaschosenasanindependentvariabletoexpressdamageexponentduetothework-energyprinciple.Anovelequivalentfatigueimpulsedensitywasproposedtodescribethenonlinearfatigue-creepinteractionbytransformingcreepimpulsedensityintofatigueimpulsedensity.Thepresentmodelcandescribecreep–fatigueinteractiondamageevolutionofAISIH13effectively,whichisconvenienttoestimatethedamageofengineeringmaterialAISIH13hottool215steel.-9- 中国科技论文在线http://www.paper.edu.cnReferences[1]L.Donati,L.Tomesani.Theeffectofdiedesignontheproductionandseamweldqualityofextruded220aluminumprofiles.[J]J.Mater.Process.Tech,(2005),164-165(20),1025-1031[2]S.N.AbRahim,M.A.Lajis,S.Ariffin.AReviewonRecyclingAluminumChipsbyHotExtrusionProcess.[J]ProcediaCIRP,(2015)26,761-766.[3]D.Delagnes,P.Lamesle,M.H.Mathon,N.Mebarki,C.Levaillant.Influenceofsiliconcontentontheprecipitationofsecondarycarbidesandfatiguepropertiesofa5%Crtemperedmartensiticsteel.[J]Mater.Sci.Eng.225A,(2005),394(1-2),435-444.[4]G.Telasang,J.DuttaMajumdar,G.Padmanabham,I.Manna.WearandcorrosionbehavioroflasersurfaceengineeredAISIH13hotworkingtoolsteel.[J]SurfaceandCoatingsTechnology,(2015),261,69-78.[5]Zhi-xinJia,Yao-weiLiu,Ji-qiangLi,Li-JunLiu,Hong-linLi.CrackgrowthbehavioratthermalfatigueofH13toolsteelprocessedbylasersurfacemelting.[J]Int.J.Fatigue,(2015),78,61-71.230[6]MohamedKchaou,RiadhElleuch,YannickDesplanques,XavierBoidin,GérardDegallaix.FailuremechanismsofH13dieonrelationtotheforgingprocess-Acasestudyofbrassgasvalves.Eng.Fail.Anal,[J](2010),17(2),403-415.[7]B.Reggiani,L.Donati,J.Zhou,L.Tomesani.Theroleofcreepandfatigueindeterminingthehigh-temperaturebehaviourofAISIH11temperedsteelforaluminiumextrusiondies.[J]J.Mater.Process.Tech,(2010),210(12),2351613-1623.[8]Yang.Xiaohua,Li.N,JZ,Jin.,Wang.T.J.Acontinuouslowcyclefatiguedamagemodelanditsapplicationinengineeringmaterials,[J]Int.J.Fatigue,(1997),19(10),687-692.[9]HuLiu,De-GuangShang,Jian-ZhongLiu,Zhen-KunGuo.Fatiguelifepredictionbasedoncrackclosurefor6156Al-alloylaserweldedjointsundervariableamplitudeloading.[J]Int.J.Fatigue,(2015),72,11-18.240[10]GuozhengKang,YujieLiu.Uniaxialratchettingandlow-cyclefatiguefailureofthesteelwithcyclicstabilizingorsofteningfeature.[J]Mater.Sci.Eng.A,(2008),472(1-2),258-268.[11]R.S.Rajpurohit,G.SudhakarRao,K.Chattopadhyay,N.C.SanthiSrinivas,VakilSingh.RatchetingfatiguebehaviorofZircaloy-2atroomtemperature.[J]J.Nuc.lMater,(2016),477,67-76.[12]R.S.Rajpurohit,G.SudhakarRao,K.Chattopadhyay,N.C.X.Yang.Lowcyclefatigueandcyclicstress245ratchetingfailurebehaviorofcarbonsteel45underuniaxialcyclicloading.[J]Int.J.Fatigue,27(9),(2005),1124-1132.[13]GuodongZhang,YanfenZhao,FeiXue,JinnaMei,ZhaoxiWang,ChangyuZhou,LuZhang.Creep-fatigueinteractiondamagemodelanditsapplicationinmodified9Cr-1Mosteel.[J]NuclearEngineeringandDesign,(2011),241(12),4856-4861.250[14]ModelforLowCycleFatigue-CreepLifePredictionofHigh-TemperatureStructures.[J]Int.J.Damage.Mech,(2012),21(7),1076-1099.[15]D.M.Ji,M.H.H.Shen,D.X.Wang,J.X.Ren.Creep-FatigueLifePredictionandReliabilityAnalysisofP91SteelBasedonAppliedMechanicalWorkDensity.[J]JournalofMaterialsEngineeringandPerformance,(2014),24(1),194-201.255[16]FuZhenXuan,YongChengLin.Reviewofcreep–fatigueenduranceandlifepredictionof316stainlesssteels.[J]InternationalJournalofPressureVessels&Piping,(2014),126-127,17-28.H13热作模具钢疲劳蠕变交互损伤模型260罗远新，杜伟奇（重庆大学，机械工程学院，重庆，400000）摘要：热作模具钢AISIH13(4Cr5MoSiV1)是典型的铝挤压模具材料，在服役过程中受到高温高压的作用导致疲劳-蠕变交互作用的损伤。为了优化结构设计和评估模具寿命，本研究开展了高温下应力控疲劳与疲劳-蠕变交互实验，通过将蠕变脉冲密度转化为疲劳脉冲密度，265引入疲劳-蠕变等效脉冲密度，建立了基于连续介质损伤力学的疲劳蠕变损伤交互模型。与实验结果对比表明该损伤模型能更好的描述其疲劳-蠕变交互作用下的损伤演化。关键词：金属材料；疲劳蠕变；连续介质力学中图分类号：TU-10-'