陶瓷材料力学性能课件

•Tensilestress,s:•Shearstress,t:Stresshasunits:N/m2orlb/in2ENGINEERINGSTRESS•Tensilestress,s:•Shear1•Elasticmodulus,E•E~curvatureatroEislargerifEoislarger.PROPERTIESFROMBONDING:E•Elasticmodulus,E•E~cu2•ElasticShearmodulus,G:t=G

g•ElasticBulkmodulus,K:•Specialrelationsforisotropicmaterials:simpletorsiontestpressuretest:Init.vol=Vo.Volchg.=DVOTHERELASTICPROPERTIES•ElasticSheart=Gg•Elasti3•Tensilestrain:•Lateralstrain:•Shearstrain:qStrainisalwaysdimensionless.(L)(-LL)ENGINEERINGSTRAIN•Tensilestrain:•Laterals4(c)2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning™isatrademarkusedhereinunderlicense.Figure6.3(a)Tensile,compressive,shearandbendingstresses.(b)IllustrationshowinghowYoung’smodulusisdefinedforelasticmaterial.(c)Fornonlinearmaterials,weusetheslopeofatangentasavariablequantitythatreplacestheYoung’smodulusconstant(c)2003Brooks/Cole,adivisio5TheTensileTest:UseoftheStress-StrainDiagramLoad-Theforceappliedtoamaterialduringtesting.StraingageorExtensometer-Adeviceusedformeasuringchangeinlengthandhencestrain.Glasstemperature(Tg)-Atemperaturebelowwhichanotherwiseductilematerialbehavesasifitisbrittle.Engineeringstress-Theappliedload,orforce,dividedbytheoriginalcross-sectionalareaofthematerial.Engineeringstrain-Theamountthatamaterialdeformsperunitlengthinatensiletest.TheTensileTest:UseoftheS6(c)2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning™isatrademarkusedhereinunderlicense.Figure6.7Aunidirectionalforceisappliedtoaspecimeninthetensiletestbymeansofthemoveablecrosshead.Thecross-headmovementcanbeperformedusingscrewsorahydraulicmechanism(c)2003Brooks/Cole,adivisio7(c)2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning™isatrademarkusedhereinunderlicense.Figure6.9Tensilestress-straincurvesfordifferentmaterials.Notethatthesearequalitative(c)2003Brooks/Cole,adivisio8•Ductilefractureisdesirableforstructuralapplications!•Classification:Ductile:warningbeforefracture,i.e.changesgeometrybeforefailureBrittle:NowarningAdaptedfromFig.8.1,Callister6e.DUCTILEVSBRITTLEFAILURE•Ductile•Classification:Duct9(c)2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning™isatrademarkusedhereinunderlicense.Figure6.10Thestress-straincurveforanaluminumalloy(c)2003Brooks/Cole,adivisio101.Initial2.Smallload3.UnloadElasticmeansreversible!ELASTICDEFORMATION1.Initial2.Smallload3.Unlo1131.Initial2.Smallload3.UnloadPlasticmeanspermanent!PLASTICDEFORMATION(METALS)31.Initial2.Smallload3.Unl12(c)2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning™isatrademarkusedhereinunderlicense.Figure6.11(a)Determiningthe0.2%offsetyieldstrengthingraycastion,and(b)upperandloweryieldpointbehaviorinalow-carbonsteel(c)2003Brooks/Cole,adivisio13TrueStressandTrueStrainTruestressTheloaddividedbytheactualcross-sectionalareaofthespecimenatthatload.TruestrainThestraincalculatedusingactualandnotoriginaldimensions,givenbyεtln(l/l0).Figure6.17Therelationbetweenthetruestress-truestraindiagramandengineeringstress-engineeringstraindiagram.ThecurvesareidenticaltotheyieldpointTrueStressandTrueStrainTru14TheBendTestforBrittleMaterialsBendtest-Applicationofaforcetothecenterofabarthatissupportedoneachendtodeterminetheresistanceofthematerialtoastaticorslowlyappliedload.Flexuralstrengthormodulusofrupture-Thestressrequiredtofractureaspecimeninabendtest.Flexuralmodulus-Themodulusofelasticitycalculatedfromtheresultsofabendtest,givingtheslopeofthestress-deflectioncurve.TheBendTestforBrittleMate15Figure6.18Thestress-strainbehaviorofbrittlematerialscomparedwiththatofmoreductilematerialsFigure6.18Thestress-strain16Figure6.19(a)Thebendtestoftenusedformeasuringthestrengthofbrittlematerials,and(b)thedeflectionδobtainedbybendingFigure6.19(a)Thebendtest17Figure6.21(a)Threepointand(b)four-pointbendtestsetupFigure6.21(a)Threepoint18陶瓷材料力学性能课件19HardnessofMaterialsHardnesstest-Measurestheresistanceofamaterialtopenetrationbyasharpobject.Macrohardness-Overallbulkhardnessofmaterialsmeasuredusingloads>2N.MicrohardnessHardnessofmaterialstypicallymeasuredusingloadslessthan2NusingsuchtestasKnoop(HK).Nano-hardness-Hardnessofmaterialsmeasuredat1–10nmlengthscaleusingextremelysmall(~100µN)forces.HardnessofMaterialsHardness20Figure6.23IndentorsfortheBrinellandRockwellhardnesstestsFigure6.23Indentorsforthe21VickersHardness,HvVickersHardness,Hv22FRACTURETOUGHNESSFracturetoughness:Kc=Ysc(pa)0.5=Y(2Egs)0.5

KcisamaterialpropertyY~1,dependsongeometryFRACTURETOUGHNESSFracturetou23increasingBasedondatainTableB5,Callister6e.Compositereinforcementgeometryis:f=fibers;sf=shortfibers;w=whiskers;p=particles.Additiondataasnoted(vol.fractionofreinforcement):1.(55vol%)ASMHandbook,Vol.21,ASMInt.,MaterialsPark,OH(2001)p.606.2.(55vol%)CourtesyJ.Cornie,MMC,Inc.,Waltham,MA.3.(30vol%)P.F.Becheretal.,FractureMechanicsofCeramics,Vol.7,PlenumPress(1986).pp.61-73.4.CourtesyCoorsTek,Golden,CO.5.(30vol%)S.T.Buljanetal.,"DevelopmentofCeramicMatrixCompositesforApplicationinTechnologyforAdvancedEnginesProgram",ORNL/Sub/85-22011/2,ORNL,1992.6.(20vol%)F.D.Gaceetal.,Ceram.Eng.Sci.Proc.,Vol.7(1986)pp.978-82.FRACTURETOUGHNESSincreasingBasedondatainTab24•Crackgrowthcondition:•Largest,moststressedcracksgrowfirst!--Result1:Maxflawsizedictatesdesignstress.--Result2:Designstressdictatesmax.flawsize.K≥KcDESIGNAGAINSTCRACKGROWTH•Crackgrowthcondition:•L25陶瓷材料力学性能课件26陶瓷材料力学性能课件27陶瓷材料力学性能课件28•Tensilestress,s:•Shearstress,t:Stresshasunits:N/m2orlb/in2ENGINEERINGSTRESS•Tensilestress,s:•Shear29•Elasticmodulus,E•E~curvatureatroEislargerifEoislarger.PROPERTIESFROMBONDING:E•Elasticmodulus,E•E~cu30•ElasticShearmodulus,G:t=G

g•ElasticBulkmodulus,K:•Specialrelationsforisotropicmaterials:simpletorsiontestpressuretest:Init.vol=Vo.Volchg.=DVOTHERELASTICPROPERTIES•ElasticSheart=Gg•Elasti31•Tensilestrain:•Lateralstrain:•Shearstrain:qStrainisalwaysdimensionless.(L)(-LL)ENGINEERINGSTRAIN•Tensilestrain:•Laterals32(c)2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning™isatrademarkusedhereinunderlicense.Figure6.3(a)Tensile,compressive,shearandbendingstresses.(b)IllustrationshowinghowYoung’smodulusisdefinedforelasticmaterial.(c)Fornonlinearmaterials,weusetheslopeofatangentasavariablequantitythatreplacestheYoung’smodulusconstant(c)2003Brooks/Cole,adivisio33TheTensileTest:UseoftheStress-StrainDiagramLoad-Theforceappliedtoamaterialduringtesting.StraingageorExtensometer-Adeviceusedformeasuringchangeinlengthandhencestrain.Glasstemperature(Tg)-Atemperaturebelowwhichanotherwiseductilematerialbehavesasifitisbrittle.Engineeringstress-Theappliedload,orforce,dividedbytheoriginalcross-sectionalareaofthematerial.Engineeringstrain-Theamountthatamaterialdeformsperunitlengthinatensiletest.TheTensileTest:UseoftheS34(c)2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning™isatrademarkusedhereinunderlicense.Figure6.7Aunidirectionalforceisappliedtoaspecimeninthetensiletestbymeansofthemoveablecrosshead.Thecross-headmovementcanbeperformedusingscrewsorahydraulicmechanism(c)2003Brooks/Cole,adivisio35(c)2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning™isatrademarkusedhereinunderlicense.Figure6.9Tensilestress-straincurvesfordifferentmaterials.Notethatthesearequalitative(c)2003Brooks/Cole,adivisio36•Ductilefractureisdesirableforstructuralapplications!•Classification:Ductile:warningbeforefracture,i.e.changesgeometrybeforefailureBrittle:NowarningAdaptedfromFig.8.1,Callister6e.DUCTILEVSBRITTLEFAILURE•Ductile•Classification:Duct37(c)2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning™isatrademarkusedhereinunderlicense.Figure6.10Thestress-straincurveforanaluminumalloy(c)2003Brooks/Cole,adivisio381.Initial2.Smallload3.UnloadElasticmeansreversible!ELASTICDEFORMATION1.Initial2.Smallload3.Unlo3931.Initial2.Smallload3.UnloadPlasticmeanspermanent!PLASTICDEFORMATION(METALS)31.Initial2.Smallload3.Unl40(c)2003Brooks/Cole,adivisionofThomsonLearning,Inc.ThomsonLearning™isatrademarkusedhereinunderlicense.Figure6.11(a)Determiningthe0.2%offsetyieldstrengthingraycastion,and(b)upperandloweryieldpointbehaviorinalow-carbonsteel(c)2003Brooks/Cole,adivisio41TrueStressandTrueStrainTruestressTheloaddividedbytheactualcross-sectionalareaofthespecimenatthatload.TruestrainThestraincalculatedusingactualandnotoriginaldimensions,givenbyεtln(l/l0).Figure6.17Therelationbetweenthetruestress-truestraindiagramandengineeringstress-engineeringstraindiagram.ThecurvesareidenticaltotheyieldpointTrueStressandTrueStrainTru42TheBendTestforBrittleMaterialsBendtest-Applicationofaforcetothecenterofabarthatissupportedoneachendtodeterminetheresistanceofthematerialtoastaticorslowlyappliedload.Flexuralstrengthormodulusofrupture-Thestressrequiredtofractureaspecimeninabendtest.Flexuralmodulus-Themodulusofelasticitycalculatedfromtheresultsofabendtest,givingtheslopeofthestress-deflectioncurve.TheBendTestforBrittleMate43Figure6.18Thestress-strainbehaviorofbrittlematerialscomparedwiththatofmoreductilematerialsFigure6.18Thestress-strain44Figure6.19(a)Thebendtestoftenusedformeasuringthestrengthofbrittlematerials,and(b)thedeflectionδobtainedbybendingFigure6.19(a)Thebendtest45Figure6.21(a)Threepointand(b)four-pointbendtestsetupFigure6.21(a)Threepoint46陶瓷材料力学性能课件47HardnessofMaterialsHardnesstest-Measurestheresistanceofamaterialtopenetrationbyasharpobject.Macrohardness-Overallbulkhardnessofmaterialsmeasuredusingloads>2N.MicrohardnessHardnessofmaterialstypicallymeasuredusingloadslessthan2NusingsuchtestasKnoop(HK).Nano-hardness-Hardnessofmaterialsmeasuredat1–10nmlengthscaleusingextremelysmall(~100µN)forces.HardnessofMaterialsHardness48Figure6.23IndentorsfortheBrinellandRockwellhardnesstestsFigure6.23Indentorsforthe49VickersHardness