Designation:C1421−16StandardTestMethodsforDeterminationofFractureToughnessofAdvancedCeramicsatAmbientTemperature1ThisstandardisissuedunderthefixeddesignationC1421;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thesetestmethodscoverthefracturetoughness,KIc,determinationofadvancedceramicsatambienttemperature.ThemethodsdetermineKIpb(precrackedbeamtestspecimen),KIsc(surfacecrackinflexure),andKIvb(chevron-notchedbeamtestspecimen).Thefracturetoughnessvaluesaredeterminedusingbeamtestspecimenswithasharpcrack.Thecrackiseitherastraight-throughcrackformedviabridgeflexure(pb),orasemi-ellipticalsurfacecrackformedviaKnoopindentation(sc),oritisformedandpropagatedinachevronnotch(vb),asshowninFig.1.NOTE1—Thetermsbend(ing)andflexurearesynonymousinthesetestmethods.1.2ThesetestmethodsareapplicabletomaterialswitheitherflatorwithrisingR-curves.Differencesintestprocedureandanalysismaycausethevaluesfromeachtestmethodtobedifferent.Formanymaterials,suchasthesiliconnitrideStandardReferenceMaterial2100,thethreemethodsgiveidenticalresultsatroomtemperatureinambientair.1.3Thefracturetoughnessvaluesforamaterialcanbefunctionsofenvironment,testrateandtemperature.Thesetestmethodsgivefracturetoughnessvaluesforspecificconditionsofenvironment,testrateandtemperature.1.4Thesetestmethodsareintendedprimarilyforusewithadvancedceramicsthataremacroscopicallyhomogeneousandmicrostructurallydense.Certainwhisker-orparticle-reinforcedceramicsmayalsomeetthemacroscopicbehaviorassumptions.Singlecrystalsmayalsobetested.1.5Thisstandardbeginswithamainbodythatprovidesinformationonfracturetoughnesstestingingeneral.Itisfollowedbyannexesandappendiceswithspecificinformationfortheparticulartestmethods.MainBodySectionScope1ReferencedDocuments2Terminology(includingdefinitions,orientationandsymbols)3Summaryof...
