Experimentalinvestigationonductilestablecrackgrowthemanatingfromwire-cutnotchinAISI4340steelOriginalResearchArticle

Anexperimentalinvestigationonthestablecrackgrowth(SCG)behaviourinAISI4340usingCTtypespecimenwithasharpslit(0.05mm)undermodeIandmixedmodes(IandII)loadingispresented.Theslitwasmadeinthespecimenthroughwirecuttingtechnique.Differentcombinationsofloadingangleϕandratiooforiginalcracklengthtospecimenwidth(a0/W)areexamined.Dataconcernedwithdirectionofinitialcrackextension,load–loadlinedisplacement(L–LLD)diagrams,initiationandmaximumloads,rangeofstablecrackgrowth,cracktipblunting,crackfrontgeometry,fracturesurfacesandtheirscanningelectronmicrographsareobtained.Anoticeablebluntingeffectisobservedpriortocrackinitiation.Althoughthecrackinitiatesfromastraightfront,aconsiderablefronttunnellingeffectoccursasthecrackextends.Undermixedmode,thecrackextensiontakesplaceinitiallyalmostalongastraightpath,inclinedwiththemaincrack.Theloadingangleandinitialcracklengthaffecttheinitiation(Pi)andmaximum(Pmax)loadssignificantly,buttheratiobetweenPmaxandPiremainsalmostconstant.Thedirectionofinitialstablecrackextensionduetomixedmodeloadingisdeterminedthroughoutanelasticfiniteelementanalysis.Thereisagoodagreementbetweentheexperimentalandpredictedresults.