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1、Author'spersonalcopyEuropeanJournalofMechanicsA/Solids27(2008)117ModificationoftheGursonModelforshearfailureK.Nahshon,J.W.Hutchinson∗SchoolofEngineeringandAppliedSciences,HarvardUniversity,Cambridge,MA02138,USAReceived8May2007;accepted22August2007Availableon
2、line30August2007AbstractRecentexperimentalevidencepointstolimitationsincharacterizingthecriticalstraininductilefracturesolelyonthebasisofstresstriaxiality.Asecondmeasureofstressstate,suchastheLodeparameter,isrequiredtodiscriminatebetweenaxisymmetricandshear
3、-dominatedstressstates.Thisisbroughtintothesharpestreliefbythefactthatmanystructuralmetalshaveafracturestraininshear,atzerostresstriaxiality,thatcanbewellbelowfracturestrainsunderaxisymmetricstressingatsignificantlyhighertriaxiality.Moreover,recenttheoretica
4、lstudiesofvoidgrowthrevealthattriaxialityaloneisinsufficienttocharacterizeimportantgrowthandcoalescencefeatures.Ascurrentlyformulated,theGursonModelofmetalplasticitypredictsnodamagechangewithstrainunderzeromeanstress,exceptwhenvoidsarenucleated.Consequently,
5、themodelexcludesshearsofteningduetovoiddistortionandinter-voidlinking.Asitstands,themodeleffectivelyexcludesthepossibilityofshearlocalizationandfractureunderconditionsoflowtriaxialityifvoidnucleationisnotinvoked.Inthispaper,anextensionoftheGursonmodelisprop
6、osedthatincorporatesdamagegrowthunderlowtriaxialitystrainingforshear-dominatedstates.TheextensionretainstheisotropyoftheoriginalGursonModelbymakinguseofthethirdinvariantofstresstodistinguishsheardominatedstates.Theimportanceoftheextensionisillustratedbyastu
7、dyofshearlocalizationoverthecompleterangeofappliedstressstates,clarifyingrecentlyreportedexperimentaltrends.TheextensionopensthepossibilityforcomputationalfractureapproachesbasedontheGursonModeltobeextendedtoshear-dominatedfailuressuchasprojectilepenetratio
8、nandshear-offphenomenaunderimpulsiveloadings.©2007ElsevierMassonSAS.Allrightsreserved.Keywords:Plasticity;Voidgrowth;Shearlocalization;Shearfracture;GursonModel;Lodeparameter1.IntroductionTheroleofstr
