AschemeforfiniteelementanalysisofmodeIandmixedmodestablecrackgrowthandacasestudywithAISI4340steelOriginalResearchArticle

Anewschemeforelastic–plasticfiniteelementanalysishasbeenproposedforthestudyofstablecrackgrowth(SCG)frominitiationtoinstabilityinbothmodeIandmixedmodes(IandII).Theschemeisbasedonnode-releasetechniqueandhelpstodeterminethevariationoffractureloadwithcrackextensionwithoutrequiringmuchcomputerstorageandtime.Theschemepermitspredictionsofloadvariationwithloadlinedisplacement(LLD),maximumfractureload,cracktipcurrentplasticzoneandcrackedgeprofile.IntheanalysistheconditionforcrackextensionateverystageoftheSCGisconsideredtobegovernedbyCTOA/CODreachingacriticalvalue.Theschemeofanalysisisdifferentfromtheonesproposedbyearlierinvestigators.ThewholeSCGisanalysedinafewstagesusingtheANSYSsoftwareandasinglediscretization.Elementarrangementinthediscretizationisdecidedfromtheverybeginning;ithasacapabilityofaccommodatingchangesinboundaryconditionsarisingoutofcrackextensioninthelaterstages.Eachstageisanalysedafreshignoringstateofstress–strainreachedatamaterialpointattheendofthepreviousstage.CasestudiesonbothmodeIandmixedmodepresentedconsideringAISI4340steel,whichiswidelyusedinnuclearpowerindustry,indicatethattheSCGthroughitcanbecharacterizedintermsofasingleCODorCTOA.Predictionsfortheinitiationandmaximumfractureloadsinboththecasescompareverycloselywiththeexperimentaldatareported.TheresultspresentedalsoincludethevalueofcriticalCOD/CTOA(0.035mm/0.0875rad)characterizingtheSCGthroughthesteelandshowthattheinitiationloadisnotsignificantlyaffectedbycracktipradiusupto0.05mm.