Modeling-Fracture-and-Failure-with-Abaqus

ModelingFractureandFailurewithAbaqusFractureandfailuremodelingallowsforproductdesignsthatmaximizethesafeoperatinglifeofstructuralcomponents.Abaqusoffersmanycapabilitiesthatenablefractureandfailuremodeling.DamageandfailureforductilemetalsIntroduction•Propermodelingtechniquesforcapturingcrack-tipsingularitiesinfracturemechanicsproblems•Propermodelingtechniquesforfinite-strain(nonlinear)fracturemechanicsproblems•UsingAbaqus/CAEtocreatemeshesappropriateforfracturestudies•Calculationofstressintensityfactorsandcontourintegralsaroundacracktip•Materialdamageandfailuremodels•Wearanderosionmodeling•Simulatingcrackgrowthusingcohesiveelements•SimulatingcrackgrowthusingVCCTforAbaqusDamageandfailureforductilemetalsIntroduction•Onsetofcracking:Theonsetofcrackingcanbestudiedinquasi-staticproblemsbyusingcontourintegrals.TheJ-integral,theCt-integral(forcreep),thestressintensityfactorsforbothhomogeneousmaterialsandinterfacialcracks,thecrackpropagationdirection,andtheT-stressarecalculatedbyABAQUS/Standard.Contourintegralscanbeusedintwo-orthree-dimensionalproblems.Inthesetypesofproblemsfocusedmeshesaregenerallyrequiredandthepropagationofacrackisnotstudied.Fracturemechanics:overviewABAQUS/Standardprovidesthefollowingmethodsforperformingfracturemechanicsstudies:•Crackpropagation:Thecrackpropagationcapabilityallowsquasi-staticcrackgrowthalongpredefinedpathstobestudiedintwo-dimensionalcases.Cracksdebondalonguser-definedsurfaces.Threecrackpropagationcriteriaareavailable,andmultiplecrackscanbeincludedintheanalysis.Contourintegralscanberequestedincrackpropagationproblems.Fracturemechanics:overview•Linespringelements:Part-throughcracksinshellscanbemodeledinexpensivelybyusinglinespringelementsinastaticprocedure.•theJ-integral,whichiswidelyacceptedasaquasi-staticfracturemechanicsparameterforlinearmaterialresponseand,withlimitations,fornonlinearmaterialresponse;•theCt-integral,whichhasanequivalentroletotheJ-integralinthecontextoftime-dependentcreepbehaviorinaquasi-staticstep.•thestressintensityfactors,whichareusedinlinearelasticfracturemechanicstomeasurethestrengthofthelocalcrack-tipfields.ContourintegralevaluationAbaqus/Standardofferstheevaluationofseveralparametersforfracturemechanicsstudies:•thecrackpropagationdirection-i.e.,theangleatwhichapreexistingcrackwillpropagate.•theT-stress,whichrepresentsastressparalleltothecrackfacesandisusedasanindicatoroftheextenttowhichparametersliketheJ-integralareusefulcharacterizationsofthedeformationfieldaroundthecrack.ContourintegralevaluationInteractionmodule:SpecialCrackCreate:Name:cracknameStepmodule:historyoutputrequesteditor:Domain:Contourintegralname:crackname,Numberofcontours:n,Type:integral_typeAbaqus/CAEUsage:•thecrackpropagationdirection-i.e.,theangleatwhichapreexistingcrackwillpropagate.•theT-stress,whichrepresentsastressparalleltothecrackfacesandisusedasanindicatoroftheextenttowhichparametersliketheJ-integralareusefulcharacterizationsofthedeformationfieldaroundthecrack.ContourintegralevaluationInteractionmodule:SpecialCrackCreate:Name:cracknameStepmodule:historyoutputrequesteditor:Domain:Contourintegralname:crackname,Numberofcontours:n,Type:integral_typeAbaqus/CAEUsage:Definingthecrackfront:DefiningthedatarequiredforacontourintegralInteractionmodule:SpecialCrackCreate:selectthecrackfront,thenselectthecracktip(intwodimensions)orcrackline(inthreedimensions)Abaqus/CAEUsage:Interactionmodule:SpecialCrackCreate:selectthecrackfront:Specifycrackextensiondirectionusing:qvectorsAbaqus/CAEUsage:Definingthecrackfront:DefiningthedatarequiredforacontourintegralCreatingthesingularity:ContourintegralevaluationInteractionmodule:SpecialCrackCreate:selectthecrackfrontandcracktip,andspecifythecrackextensiondirection:Singularity:Midsidenodeparameter:n,Collapsedelementside,singlenodeAbaqus/CAEUsage:Creatingasquarerootsingularity:(suitableforlinearelasticity).Creatingthesingularity:ContourintegralevaluationInteractionmodule:SpecialCrackCreate:selectthecrackfrontandcracktip,andspecifythecrackextensiondirection:Singularity:Midsidenodeparameter:n,Collapsedelementside,duplicatenodesAbaqus/CAEUsage:Creatinga1/rsingularity:(suitableforperfectplasticity).Crackpropagationanalysis:Crackpropagationanalysis•allowsforfivetypesoffracturecriteria—criticalstressatacertaindistanceaheadofthecracktip,criticalcrackopeningdisplacement,cracklengthversustime,VCCT(theVirtualCrackClosureTechnique),andthelow-cyclefatiguecriterionbasedontheParislaw.•modelsquasi-staticcrackgrowthintwodimensions(planarandaxisymmetric)foralltypesoffracturecriteriaandinthreedimensions(solid,shells,andcontinuumshells)forVCCTandthelow-cyclefatiguecriteria•requiresthatyoudefinetwodistinctinitiallybondedcontactsurfacesbetweenwhichthecrackwillpropagate.Criticalstresscriterion:CrackpropagationanalysisDistancespecificationforthecriticalstresscriterionCriticalcrackopeningdisplacementcriterion:CrackpropagationanalysisDistancespecificationforthecriticalcrackopeningdisplacementcriterionCracklengthversustimecriterion:CrackpropagationanalysisCrackpropagationasafunction