金属材料失效在abaqus中的应用

DYNAMICFAILUREMODELS

18.2.8DYNAMICFAILUREMODELS Product:Abaqus/ExplicitReferences

????????“Equationofstate,”Section17.9.1“Classicalmetalplasticity,”Secti on18.2.1“Rate-dependentyield,”Section18.2.3“Johnson-

Cookplasticity,”Section18.2.7“Materiallibrary:overview,”Section16.1.1“I nelasticbehavior,”Section18.1.1*SHEARFAILURE

*TENSILEFAILUREOverview

Theprogressivedamageandfailuremodelsdescribedin“Damageandfailuref orductilemetals:overview,”Section19.2.1,aretherecommendedmethodfo rmodelingmaterialdamageandfailureinAbaqus;thesemodelsaresuitablefo rbothquasi-

staticanddynamicsituations.Abaqus/Explicitofferstwoadditionalelementf ailuremodelssuitableonlyforhigh-strain-

ratedynamicproblems.Theshearfailuremodelisdrivenbyplasticyielding.Th etensilefailuremodelisdrivenbytensileloading.Thesefailuremodelscanbeu sedtolimitsubsequentload-

carryingcapacityofanelement(uptothepointofremovingtheelement)once astresslimitisreached.Bothmodelscanbeusedforthesamematerial.

Theshearfailuremodel: ????? ??? ?

?isdesignedforhigh-strain-

ratedeformationofmanymaterials,includingmostmetals;usestheequivale ntplasticstrainasafailuremeasure;offerstwochoicesforwhatoccursuponfai lure,includingtheremovalofelementsfromthemesh;canbeusedinconjuncti onwitheithertheMisesortheJohnson-

Cookplasticitymodels;andcanbeusedinconjunctionwiththetensilefailure model.isdesignedforhigh-strain-

ratedeformationofmanymaterials,includingmostmetals;usesthehydrosta ticpressurestressasafailuremeasuretomodeldynamicspallorapressurecut off;offersanumberofchoicesforwhatoccursuponfailure,includingtheremo valofelementsfromthemesh;canbeusedinconjunctionwitheithertheMises ortheJohnson-

Cookplasticitymodelsortheequationofstatematerialmodel;and

canbeusedinconjunctionwiththeshearfailuremodel.Thetensilefailuremod el:

18.2.8–1

DYNAMICFAILUREMODELS

Shearfailuremodel

TheshearfailuremodelcanbeusedinconjunctionwiththeMisesortheJohnso n-

CookplasticitymodelsinAbaqus/Explicittode?neshearfailureofthematerial.

Shearfailurecriterion

Theshearfailuremodelisbasedonthevalueoftheequivalentplasticstrainatel ementintegrationpoints;failureisassumedtooccurwhenthedamageparam eterexceeds1.Thedamageparameter,,isde?nedaswhereisanyinitialvalueo ftheequivalentplasticstrain,isanincrementoftheequivalentplasticisthestra inatfailure,andthesummationisperformedoverallincrementsintheanalysis.s train,

Thestrainatfailure,,isassumedtodependontheplasticstrainrate,;adimensio nlesspressure-

deviatoricstress(wherepisthepressurestressandqistheMisesstress);tempe rature;andprede?ned?eldvariables.Therearetwowaystode?nethestrainat failure,.Oneistousedirecttabulardata,wherethedependenciesaregivenina tabularform.theanalyticalformproposedbyJohnsonandCookcanbeinvoke d(see“Johnson-Cookplasticity,”Section18.2.7,formoredetails).

Whendirecttabulardataareusedtode?netheshearfailuremodel,thestraina tfailure,,mustbegivenasatabularfunctionoftheequivalentplasticstrainrate,t hepressure-

deviatoricratio,temperature,andprede?ned?eldvariables.Thismethodreq uirestheuseoftheMisesplasticitymodel.

FortheJohnson-

Cookshearfailuremodel,youmustspecifythefailureparameters,– (see“Johnson-

Cookplasticity,”Section18.2.7,formoredetailsontheseparameters).Theshe arfailuredatamustbecalibratedatorbelowthetransitiontemperature,,de?n edin“Johnson-

Cookplasticity,”Section18.2.7.ThismethodrequirestheuseoftheJohnson- Cookplasticitymodel.InputFileUsage:Usebothofthefollowingoptionsforth eMisesplasticitymodel:

*PLASTIC,HARDENING=ISOTROPIC *SHEARFAILURE,TYPE=TABULAR

UsebothofthefollowingoptionsfortheJohnson-Cookplasticitymodel: *PLASTIC,HARDENING=JOHNSONCOOK *SHEARFAILURE,TYPE=JOHNSONCOOK Elementremoval

Whentheshearfailurecriterionismetatanintegrationpoint,allthestresscom

ponentswillbesettozeroandthatmaterialpointfails.Bydefault,ifallofthemat erialpointsatanyonesectionofanelementfail,theelementisremovedfromth emesh;itisnotnecessaryforallmaterialpointsintheelementtofail.Forexamp le,ina?rst-orderreduced-

integrationsolidelementremovaloftheelementtakesplaceassoonas

18.2.8–2

DYNAMICFAILUREMODELS

itsonlyintegrationpointfails.However,inashellelementallthrough- the-

thicknessintegrationpointsmustfailbeforetheelementisremovedfromthe mesh.Inthecaseofsecond-orderreduced-

integrationbeamelements,failureofallintegrationpointsthroughthesectio nateitherofthetwoelementintegrationlocationsalongthebeamaxisleads,b ydefault,toelementremoval.Similarly,inthemodi?edtriangularandtetrahe dralsolidelementsfailureatanyoneintegrationpointleads,bydefault,toele mentremoval.Elementdeletionisthedefaultfailurechoice.

Analternativefailurechoice,wheretheelementisnotdeleted,istospecifytha twhentheshearfailurecriterionismetatamaterialpoint,thedeviatoricstress componentswillbesettozeroforthatpointandwillremainzerofortherestoft hecalculation.Thepressurestressisthenrequiredtoremaincompressive;tha tis,ifanegativepressurestressiscomputedinafailedmaterialpointinanincre

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