ABAQUS中的钢的Chaboche非线性循环硬化本构用法

1Copyright©2014byASMEProceedingsoftheASME2014PressureVessels&PipingConferencePVP2014July20-24,2014,Anaheim,California,USAPVP2014-28772ADDITIONALGUIDANCEFORINELASTICRATCHETINGANALYSISUSINGTHECHABOCHEMODELWilliamF.Weitze,P.E.StructuralIntegrityAssociates,Inc.SanJose,California,USATimothyD.GilmanStructuralIntegrityAssociates,Inc.SanJose,California,USAABSTRACTThispaperbuildsonPVP2013-98150byKalnins,Rudolph,andWilluweit[1],whichdocumentedtwocalibrationprocessesfordeterminingtheparametersoftheChabochenonlinearkinematichardening(NLK)materialmodelforstainlesssteel,andtestedthematerialmodelusingapressurizedcylindricalshellsubjectedtothermalcycling.Thecurrentpaperexamines(1)whetheraChabocheNLKmodelwithonlytwoterms(ratherthanfourasinPVP-98150)issufficientlyaccurate,(2)useoftheANSYSprogramformaterialmodelrefinementandfiniteelementanalysis,and(3)analysisusingtemperature-dependentNLKmodelparameters,againusingANSYS.INTRODUCTIONRatchetingisprogressivedistortionofacomponentundercyclicduty.Takentotheextreme,itcanleadtoanunstablecomponentgeometryandsubsequentcollapse.SectionIIIoftheASMEBoilerandPressureVesselCodecontainsequationstopreventratchetinginnuclearreactorcomponents,suchasEquations10,12,and13ofNB-3650,forexample[2].Inelasticanalysisisusedtoevaluateratchetingwhenitisnecessarytoremoveexcessconservatism.Whenaninelasticanalysisisperformed,thedesignisconsideredacceptableifeithershakedownoccursafterafewcycles,orthemaximumaccumulatedlocalstraindoesnotexceed5%(forcertainmaterialsonly)[2,NB-3228.4(b)].However,theASMECodedoesnotprovideguidanceastohowtheinelasticanalysisshouldbeperformed.Arelativelysimpleinelasticanalysisapproachwouldbetoassumeelastic-perfectlyplasticbehavior.However,thisapproachisstillsignificantlyconservativecomparedtotheactualbehaviorofductilematerials.Workiscurrentlyunderwaytodevelopmoreaccurateinelasticanalysismethodology.TheChabocheNLKmaterialmodelissufficientlysophisticatedtomodelratchetingbehavior,butadditionalworkisneededtofurtheritsapplicationtorealworldproblems.PaperPVP2013-98150byKalnins,Rudolph,andWilluweit[1]providedguidanceforratchetinganalysisusingtheChabocheNLKmaterialmodelforstainlesssteel.Thispapercontinuesthislineofworkasdescribedintheabstract.NOMENCLATURECK=materialparameterfortheKthcomponentEy=modulusofelasticityK=1toN,aChabochemodelcomponentN=numberofChabochemodelcomponentsRp0.2=0.2%proofstress=backstressK=backstressfortheKthcomponentNLK=totalbackstressfromNLKmodelK=materialparameterfortheKthcomponent=uniaxialengineeringstrainp=uniaxialplasticengineeringstraintrue=uniaxialtruestrain=engineeringstress0=initialyieldstressattheelasticlimittrue=truestressuts=ultimatetensilestrengthys=yieldstrengthDEVELOPMENTOFCHABOCHEMODELPARAMETERSAsinPVP2013-98150,theChabochemodelisbasedonthemonotonicstress-straincurveobtainedfromatensionspecimensubjectedtouniaxialloading[1,Section3.1].Thisisconservativebecauseitneglectsthebeneficialcyclichardeningthatoccurswithstainlesssteels.SpecificcurvesaretakenfromASMECodeSectionVIII,Division2,Annex3-D,paragraph3-D.3[2],forSA-312TP304at400°Faswaspreviouslydone[1,Section3.2],aswellasthe70°Fcurvefromthesamesource.Table1showsselectedpropertiesforthesecurves.DownloadedFrom::©2014byASMETable1:SelectedPropertiesofSA-312TP304at70°F,inksiat70°F,inMPaat400°F,inksiat400°F,inMPauts75.0517.1064.0441.26ys30.0206.8420.7142.72Ey2830019511926400182019Asbefore,thetruestress-truestraincurvefromSectionVIII-Division2isconvertedtoengineeringstress-engineeringstrainforthecalibrationasfollows[1,Section3.2]:=exp(true)–1(1)=true/(1+)(2)Figure1showsthetwostress-straincurvesafterconversion,andFigure2showstheportionofthecurvesusedinthecurrentanalysis.Figure1:EngineeringStress-EngineeringStrainCurvesBasedonSectionVIIIDivision2Figure2:CurvesUpto5%EngineeringStrainAsbefore,theinitialyieldstressattheelasticlimit,0,isestimatedasequalto0.55timesthe0.2%proofstress,Rp0.2[1,Section3.3].Table2showsRp0.2andtheelasticlimitforthetwocurves.Table2:DeterminationofElasticLimitT,°FRp0.2,ksi0,ksi7020.111.05540029.2316.0765Thebackstressisthetranslationoftheyieldsurfaceinstressspace,andiscalculatedas[1,Section3.4]:=–0(3)Plasticstrainisapproximatedasthetotalengineeringstrainminusthestrainattheelasticlimit.Figure3showsthebackstressforthetwostress-straincurves;thesamescalesarechosenasinFigure2foreaseofcomparison.Figure3:BackstressasaFunctionofPlasticStrainTheChabochematerialmodelisusedtoperformacurvefitofthecurvesinFigure3sothatratchetinganalysescanbeperformed.ForaChabochemodelofNcomponents,theNLKbackstressisasfollows[1,Section3.4]:K=(CK/K)[1–exp(-Kp)](4)NLK=∑K(5)ThereareseveraldifferencesbetweenthecurrentanalysisandtheanalysisinPVP2013-98150:ThecurrentanalysesuseN=2insteadof4.Inadditiontotheanalysisusingthe400°Fmaterialmodel,asecondrunismadeusingthe70°Fmodel.Athirdrunismadeusingtemperature-dependentproperties.DownloadedFrom: