Designation:E2899−15StandardTestMethodforMeasurementofInitiationToughnessinSurfaceCracksUnderTensionandBending1ThisstandardisissuedunderthefixeddesignationE2899;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethoddescribesthemethodfortestingfatigue-sharpened,semi-ellipticallyshapedsurfacecracksinrectangularflatpanelssubjectedtomonotonicallyincreasingtensionorbending.Testsquantifythecrack-tipconditionsatinitiationofstablecrackextensionorimmediateunstablecrackextension.1.2Thistestmethodappliestothetestingofmetallicmaterialsnotlimitedbystrength,thickness,ortoughness.Materialsareassumedtobeessentiallyhomogeneousandfreeofresidualstress.Testsmaybeconductedatanyappropriatetemperature.Theeffectsofenvironmentalfactorsandsustainedorcyclicloadsarenotaddressedinthistestmethod.1.3Thistestmethoddescribesallnecessarydetailsfortheusertotestfortheinitiationofcrackextensioninsurfacecracktestspecimens.Specificrequirementsandrecommendationsareprovidedfortestequipment,instrumentation,testspecimendesign,andtestprocedures.1.4Testsofsurfacecracked,laboratory-scalespecimensasdescribedinthistestmethodmayprovideamoreaccurateunderstandingoffull-scalestructuralperformanceinthepres-enceofsurfacecracks.Theprovidedrecommendationshelptoassuretestmethodsanddataareapplicabletotheintendedpurpose.1.5Thistestmethodprescribesaconsistentmethodologyfortestandanalysisofsurfacecracksforresearchpurposesandtoassistinstructuralassessments.Themethodsdescribedhereutilizeaconstraint-basedframework(1,2)2toevaluatethefracturebehaviorofsurfacecracks.NOTE1—Constraint-basedframework.Inthecontextofthistestmethod,constraintisusedasadescriptorofthethree-dimensionalstressandstrainfieldsinthenearvicinityofthecracktip,wherematerialcontractionsduetothePoissoneffectmaybesuppressedandthereforeprodu...
