【英文标准名称】:StandardTestMethodforDeterminationofSlowCrackGrowthParametersofAdvancedCeramicsbyConstantStress-RateFlexuralTestingatElevatedTemperatures
【原文标准名称】:高温下用恒定应力速度挠曲试验测定高级陶瓷的慢裂增长系数的标准试验方法
【标准号】:ASTMC1465-2008
【标准状态】:现行
【国别】:美国
【发布日期】:2008
【实施或试行日期】:
【发布单位】:美国材料与试验协会(US-ASTM)
【起草单位】:C28.01
【标准类型】:(TestMethod)
【标准水平】:()
【中文主题词】:
【英文主题词】:advancedceramics;constantstress-ratetesting;elevatedtemperatures;flexuralstrength;flexuraltesting;four-pointflexure;slowcrackgrowth;slowcrackgrowthparameters;Advancedceramics;Constantstress-rateflexuraltesting;Cracking--crackgro
【摘要】:Formanystructuralceramiccomponentsinservice,theiruseisoftenlimitedbylifetimesthatarecontrolledbyaprocessofslowcrackgrowth.Thistestmethodprovidestheempiricalparametersforappraisingtherelativeslowcrackgrowthsusceptibilityofceramicmaterialsunderspecifiedenvironmentsatelevatedtemperatures.ThistestmethodissimilartoTestMethodC1368withtheexceptionthatprovisionsfortestingatelevatedtemperaturesaregiven.Furthermore,thistestmethodmayestablishtheinfluencesofprocessingvariablesandcompositiononslowcrackgrowthaswellasonstrengthbehaviorofnewlydevelopedorexistingmaterials,thusallowingtailoringandoptimizingmaterialprocessingforfurthermodification.Insummary,thistestmethodmaybeusedformaterialdevelopment,qualitycontrol,characterization,andlimiteddesigndatagenerationpurposes.Note38212;Datageneratedbythistestmethoddonotnecessarilycorrespondtocrackvelocitiesthatmaybeencounteredinserviceconditions.Theuseofdatageneratedbythistestmethodfordesignpurposesmayentailconsiderableextrapolationandlossofaccuracy.Inthistestmethod,theflexuralstresscomputationisbasedonsimplebeamtheory,withtheassumptionsthatthematerialisisotropicandhomogeneous,themoduliofelasticityintensionandcompressionareidentical,andthematerialislinearlyelastic.Theaveragegrainsizeshouldbenogreaterthanonefiftieth(1/50)ofthebeamthickness.Inthistestmethod,thetestspecimensizesandtestfixtureswerechoseninaccordancewithTestMethodC1211,whichprovidesabalancebetweenpracticalconfigurationsandresultingerrors,asdiscussedinRefs(7,8).Onlythefour-pointtestconfigurationisusedinthistestmethod.Inthistestmethod,theslowcrackgrowthparameters(nandD)aredeterminedbasedonthemathematicalrelationshipbetweenflexuralstrengthandappliedstressrate,logx03C3;f=[1/(n+1)]logx02D9;x03C3;+logD,togetherwiththemeasuredexperimentaldata.Thebasicunderlyingassumptiononthederivationofthisrelationshipisthatslowcrackgrowthisgovernedbyanempiricalpower-lawcrackvelocity,v=A[KI/KIC]n(seeAppendixX1).Note48212;Therearevariousotherformsofcrackvelocitylawswhichareusuallymorecomplexorlessconvenientmathematically,orboth,butmaybephysicallymorerealistic(9).Themathematicalanalysisinthistestmethoddoesnotcoversuchalternativecrackvelocityformulations.Inthistestmethod,themathematicalrelationshipbetweenflexuralstrengthandstressratewasderivedbasedontheassumptionthattheslowcrackgrowthparameterisatleastnx2265;5(3,10).Therefore,ifamaterialexhibitsaveryhighsusceptibilitytoslowcrackgrowth,thatis,nx003C;5,specialcareshouldbetakenwheninterpretingtheresults.Themathematicalanalysisoftestresultsaccordingtothemethodin4.4assumesthatthematerialdisplaysnorisingR-curvebehavior,thatis,noincreasingfractureresistance(orcrack-extensionresistance)withincreasingcracklength.Itshouldbe......