Int.J.FatigueVol.20,No.7,pp.495–501,19981998ElsevierScienceLtd.AllrightsreservedPrintedinGreatBritain0142–1123/98/$19.00PII:S0142-1123(98)00018-8AfatiguedamageaccumulationmodelbasedoncontinuumdamagemechanicsandductilityexhaustionGuangxuCheng*andAlanPlumtree†*DepartmentofChemicalEngineeringandMachinery,Xi’anJiaotongUniversity,Xi’an,ShaanxiProvince710049,P.R.China†DepartmentofMechanicalEngineering,UniversityofWaterloo,200UniversityAvenueWest,Waterloo,Ontario,N2L3GI,Canada(Received4February1997;revised18October1997;accepted15December1997)Usingcontinuumdamagemechanics,afatiguedamageaccumulationmodelrelatedtoductilityexhaustionhasbeendeveloped.Thismodelwasappliedtostudyfatiguedamageevolutioninapressurevesselsteelandtwo-levelcyclictestshavebeencarriedouttoverifythedamageaccumulationmodel.Theexperimentalresultsshowedthatadamagevariable,D,basedonductilityexhaustioncanbeusedtomeasurecumulativedamageandprovideagoodestimateofthefatiguedamageprocess,aswellastopredictthefatiguelife.1998ElsevierScienceLtd.Allrightsreserved(Keywords:fatiguedamageaccumulation;continuumdamagemechanics;ductilityexhaustion)INTRODUCTION͸ni=−␣1forcrackgrowth(2)Inmostengineeringstructures,loadbearingcompo-(1)Ninentsaresubjectedtovariableamplitudeloadhistories.where,␣istheproportionoflifespentincrackInordertopredictthelifeofthesecomponents,dam-initiation.Thesebilinearequationscangivegoodagemustbeevaluatedandarelationshipformulatedagreementwiththeexperimentalresults3,providedthetodescribedamageaccumulationandfatiguelife.valueoftheconstant␣isknownforthedifferentObviously,thestudyofdamageevolutionisanstressamplitudes.importantresearchaspectoffatiguefailureandsafeAlternatively,nonlineardamageaccumulationequa-designcriteria.tionshavebeenproposed.AtypicalequationwasAvarietyofdamageaccumulationmodelshavebeenpresentedbyGratts4,proposedandMiner’slinearrule1hasreceivedmuchmattentionduetoitssimplicity:ni͸ͩͪ=C(3)Nƒnn͸i=1(1)Nƒi=1Here,bothC(CÞ1)andmarematerialconstants.