Nonlinear delamination mechanics for thin films

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1、J.Merh.Ph.x.Solds,Vol45,No.7,pp.1137-1159.1997c~1997ElsevierScienceLtdPergamonPrintedmGreatBritain.Allrightsreserved0022-5096197$17.00+O00PII:SOO22-5096(96)00122-6NONLINEARDELAMINATIONMECHANICSFORTHINFILMSYUEGUANGWEIandJOHNW.HUTCHINSONDivisionofEngineeringandAppliedSciences.HarvardUniversity.Cam

2、bridge.MA02138,U.S.A(Rewired5August1996;inreri.wtl,fimn8Nowmhcr1996)ABSTRACTDelaminationofprestressedthinfilmsonthicksubstratesisanalysedaccountingforplasticdissipationineitherthesubstrateorfilm.Emphasisisonlargescaleyieldingwhereintheheightoftheplasticzoneatthepropagatinginterfacecracktipiscompa

3、rabletothefilmthickness.Suchconditionsarecommonforbothmetalandpolymerthinfilmsonelasticsubstratesorforceramiccoatingsonmetalsubstrateswhentheinterfacebetweenthefilmandsubstrateisreasonablystrong.Underlargescaleyielding,thenotionofathickness-independentinterfacetoughnessnolongerpertains,andanonlin

4、earfracturemechanicsisrequiredtoquantifydelamination.Twosuchapproachesarepursuedinthispaperusingmodelsbasedontheattainmentofcriticalconditionsattheinterfacecracktipwithintheplasticzone.Steady-statefilmdelaminationisanalysedforconditionswhereyieldingoccurseitherinthefilmorinthesubstrate,andcritica

5、lcombinationsofprestressandthicknessarepredicted.Thetheoryisappliedtoarecentsetofexperimentsoncopperfilmsdelaminatingfromsilicasubstrates.r{Tj1997ElsevierScienceLtdKeywords:A.cracktipplasticity,A.fracturetoughness.1.INTRODUCTIONAthinisotropicfilmofthicknesshbondedtoathicksubstrateissubjecttoaunif

6、orm,equi-biaxialstressgR,asdepictedfortwotypesofprobleminFig.1.Theelasticenergyperunitareainthebondedfilmis(1-~)ha~/E,whereEandvaretheYoungsmodulusandPoissonsratioofthefilm,respectively.Whendelaminationoccursasalonginterfacecrackreleasingtheelasticenergyinthefilmwithoutplasticdeformationinthefilm

7、,theenergyreleaserateperunitofcrackadvanceisG=l-vha;(1.1)2E(Thefilmissubjecttotheplanestrainconstraintinthex3directionleavingaresidualstressc733=(1-v)aRinthedetachedfilm.)Foraperfectlybrittlesystem,thecriticalcondition