A Procedure to Generate Input Data of Cyclic Softe

NordiskkernesikkerhedsforskningNorrænarkjarnöryggisrannsóknirPohjoismainenydinturvallisuustutkimusNordiskkjernesikkerhetsforskningNordiskkärnsäkerhetsforskningNordicnuclearsafetyresearchNKS-150ISBN978-87-7893-213-6AProceduretoGenerateInputDataofCyclicSofteningandHardeningforFEMAnalysisfromConstantStrainAmplitudeFatigueTestsinLCFRegimeUrpoSarajärviandOtsoCronvallVTT,FinlandMarch2007AbstractFatigueisproducedbycyclicapplicationofstressesbymechanicalorthermalloading.Themetalsubjectedtofluctuatingstresswillfailatstressesmuchlowerthanthoserequiredtocausefractureinasingleapplicationofload.Thekeypa-rametersaretherangeofstressvariationandthenumberofitsoccurrences.Low-cyclefatigue,usuallyinducedbymechanicalandthermalloads,isdistin-guishedfromhigh-cyclefatigue,mainlyassociatedwithvibrationorhighnumberofsmallthermalfluctuations.Numericalmodelsdescribingfatiguebehaviourofausteniticstainlesspipingsteelsundercyclicloadingandtheirapplicabilityformodellingoflow-cycle-fatiguearediscussedinthisreport.Inordertodescribethecyclicbehaviourofthematerialforanalysiswithfiniteelementmethod(FEM)basedanalysiscodeABAQUS,thetestdata,i.e.stress-straincurves,havetobeprocessed.Acodetoprocessthedataallthroughthetestdurationwasdevelopedwithinthisstudy.Adescriptionofthiscodeisgivenalsointhisreport.InputdataforABAQUSwasobtainedtodescribebothkine-maticandisotropichardeningproperties.Further,bycombiningtheresultdataforvariousstrainamplitudesamathematicexpressionwasbecreatedwhichal-lowsdefiningaparametersurfaceforcyclic(i.e.isotropic)hardening.Inputdataforanystrainamplitudewithintherangeofminimumandmaximumstrainampli-tudesofthetestdatacanbeassessedwiththehelpofthedeveloped3Dstress-strainsurfacepresentation.Themodellingofthefatigueinducedinitiationandgrowthofcrackswasnotcon-sideredinthisstudy.Ontheotherhand,aconsiderablepartofthefatiguelifeofnuclearpowerplant(NPP)pipingcomponentsisspentinthephaseprecedingtheinitiationandgrowthofcracks.KeywordsFatigue,low-cycle,austeniticstainlesssteel,workhardening,modelling,FEM,ABAQUSNKS-150ISBN978-87-7893-213-6Electronicreport,March2007ThereportcanbeobtainedfromNKSSecretariatNKS-776P.O.Box49DK-4000Roskilde,[e-mail]-R-11555-0626.4.2007AProceduretoGenerateInputDataofCyclicSofteningandHardeningforFEMAnalysisfromConstantStrainAmplitudeFatigueTestsinLCFRegimeAuthorsSarajärvi,Urpo,Cronvall,OtsoConfidentialityPublicRESEARCHREPORTVTT-R-11555-061(31)Report’stitleAProceduretoGenerateInputDataofCyclicSofteningandHardeningforFEMAnalysisfromConstantStrainAmplitudeFatigueTestsinLCFRegimeCustomer,contactperson,addressOrderreferenceSTUKProjectnameProjectnumber/ShortnameINPUTVÄSYMA3573/Author(s)PagesSarajärvi,Urpo,Cronvall,Otso31/KeywordsReportidentificationcodeFatigue,low-cycle,austeniticstainlesssteel,workhardening,modelling,FEM,ABAQUSVTT-R-11555-06SummaryFatigueisproducedbycyclicapplicationofstressesbymechanicalorthermalloading.Themetalsubjectedtofluctuatingstresswillfailatstressesmuchlowerthanthoserequiredtocausefractureinasingleapplicationofload.Thekeyparametersaretherangeofstressvariationandthenumberofitsoccurrences/1/.Low-cyclefatigue,usuallyinducedbymechanicalandthermalloads,isdistinguishedfromhigh-cyclefatigue,mainlyassociatedwithvibrationorhighnumberofsmallthermalfluctuations/1/.Numericalmodelsdescribingfatiguebehaviourofausteniticstainlesspipingsteelsundercyclicloadingandtheirapplicabilityformodellingoflow-cycle-fatiguearediscussedinthisreport.Inordertodescribethecyclicbehaviourofthematerialforanalysiswithfiniteelementmethod(FEM)basedanalysiscodeABAQUS,thetestdata,i.e.stress-straincurves,havetobeprocessed.Acodetoprocessthedataallthroughthetestdurationwasdevelopedwithinthisstudy.Adescriptionofthiscodeisgivenalsointhisreport.InputdataforABAQUSwasobtainedtodescribebothkinematicandisotropichardeningproperties.Further,bycombiningtheresultdataforvariousstrainamplitudesamathematicexpressionwasbecreatedwhichallowsdefiningaparametersurfaceforcyclic(i.e.isotropic)hardening.Inputdataforanystrainamplitudewithintherangeofminimumandmaximumstrainamplitudesofthetestdatacanbeassessedwiththehelpofthedeveloped3Dstress-strainsurfacepresentation.Themodellingofthefatigueinducedinitiationandgrowthofcrackswasnotconsideredinthisstudy.Ontheotherhand,aconsiderablepartofthefatiguelifeofnuclearpowerplant(NPP)pipingcomponentsisspentinthephaseprecedingtheinitiationandgrowthofcracks.ConfidentialityPublicEspoo14.2.2007SignaturesEilaLehmusTechnologyManagerUrpoSarajärviResearchScientistVTT’scontactaddressP.O.Box1000,FI-02044VTTDistribution(customerandVTT)STUK:Registry(4),KeskinenR.(1),HytönenY.(1);FNS:NeuvonenA.(1);TVO:PulkkinenE.(1kpl);NKS(1);VTT:Archive(1)TheuseofthenameoftheTechnicalResearchCentreofFinland(VTT)inadvertisingorpublicationinpartofthisreportisonlypermissiblewithwrittenauthorisationfromtheTechnicalResearchCentreofFinland.RESEARCHREPORTVTT-R-11555-062(31)PrefaceThisreporthasbeenpreparedundertheresearchprojectINPUTVÄSYMA.TheprojectisapartofSAFIR,whichisanationalnucl