EvaluationofFractureToughnessofMaterials

UsingInstrumentedIndentationTechnique:Ductile/BrittleFractureModels2013.08.30.WonJeJoContentsIntroductionIndentationFractureToughnessModels-BrittlefracturemodelDuctilefracturemodelVerificationoftheModelsComparisonbetweenfracturetestresultsandIITresultsApplicationsatlowtemperatureBasicconceptofindentationfracturetoughnessFracturetestCrackpropagationandfractureIndenterIITNocrackandnofractureIssueofindentationfracturetoughnessWhatisacorrelationbetweenfracturetestandIIT?Inthecaseofmetals,ConstrainteffectaheadofacracktipPlasticregionconstrainedbyelasticregionbeneathanindenterSimilarconstrainteffectR=250mIndenter[Material:APIX70]loadingConstrainteffect2.13.22.33.0TriaxialityofcracktipTriaxialityofindentationSENBIndentationIndentationfracturetoughnessAnalogoussituationEnergyconcept=RequiredenergyforcrackpropagationEquivalentfractureenergyinIndentationAnalysisofindentationprocessIndentationprocessFormationofaplasticzonetothesurfaceFormationofafully-developedplasticzone

(c/aisconstant)Expansionofplasticzone(c/aincrease)cacaAssumptionOnsetofformationofafully-developedplasticzone=Maximumstrainenergybeneaththeindenter≈Formationofequivalentfractureenergyh*c/ahh*BrittlematerialsDuctilematerialsFracturesurfaceDeformationRelativelylittleornodeformationLargeplasticdeformationCriterionStresscontrolledcriticalfracturestressatthecracktip(sf)Straincontrolledcriticalfracturestrainatthecracktip(ef)FormationoffractureenergyWhenstressreachedcriticalfracturestressWhenstrainreachedcriticalfracturestrainFractureBehaviorBrittleFractureModelDuctileFractureModelBrittleFractureModelCriterionCriticalindentationdepth(h*)εrrCriticalstress(pressure)ath*CriterionAssumptionOnsetofformationtoa

fully-developedplasticzone=FormationofEquivalentfractureenergyApplicationofindentationtheoriesStep1Yieldingrightoutsidethecontactarea→FormationofaplasticzonetothesurfaceStep2Expansionoftheplasticzone→Formationoffully-developedplasticzonecah*HertzelasticcontacttheoryStressoutsidethecontactarea(r≥a)Whenaradialstressattheedgeofthecontactarea(r=a)

satisfiedyieldingcriterionBy

VonMises’yieldcriterionExpandingcavitymodel(E-Ptheory)Stresswithinplasticzone(a≤r≤c)Changeofthecorepressure(r=a)untilformingthefully-developedplasticzonebyK.E.Puttick(1977)coreCriterionofequivalentfractureenergyStep1Thetotalpressurerequiredforequivalentfractureenergy,Step2Fracturetoughnessforbrittlematerial

Pm-hcurve

Indentationload-depthcurve-Meancontactpressureateachunloadingdepth(1)Indentationtesting(6)Indentationfracturetoughness(KJC)(2)Measuringσys&DeterminingPmc-σysfromanalyzingL-hcurve(3)FittingPm-hcurve-(4)Determiningh*-InsertingdeterminedPmcintoPm-hcurve(5)Equivalentfractureenergyuntilh*DuctileFractureModelCriterionCriticalindentationdepth(h*)εrrCriticalstrainath*CriterionCriticalstrainath*CriterionAbsorbedstrainenergyuntilfracturestrain=Toughness(tensileenergy)AssumptionElasticenergyreleasedduetothecrackgrowthisequaltotheamountofplasticworkaheadofthecracktip.[PeelandFrosyth,1973]Plasticworkdoneperunitarear:theradiusoftheplasticzoneUT:plasticworkdoneperunitvolumeForsmallscaleyielding,Elasticenergyreleasedperunitarea〓Plasticwork[Mechanicalmetallurgy,G.E.Dieter]Plasticworkdone

=AreaUndertheStress-StrainCurvesR:flowstressef:engineeringfracturestrainMechanicalparametersEstimationfromindentationparametersPlasticzonesizeFracturestrainMeasuredparametersElasticpropertiesvs.PlasticpropertiesFunctionofuniformstrain

YieldstrengthUltimatetensilestrengthElasticmodulusPoisson’sratio,n=0.3FracturetoughnessrcefMeasuredby

indentationtestPlasticzonesize,rcPPlasticflowElasticconstraintPlasticzoneAbalancebetweenplasticflow

andelasticconstraintDominantelasticconstraintDominantplasticflowSmallPZSLargePZSResilienceFracturestrain,efExperimentalrelationbetweentrueuniformstrainandengineeringfracturestrain,PlasticzonesizeFracturestrainMeasuredparametersFracturetoughnessFracturetoughnessforductilematerialContentsIntroductionIndentationFractureToughnessModels-BrittlefracturemodelDuctilefracturemodelVerificationoftheModelsComparisonbetweenfracturetestresultsandIITresultsApplicationsatlowtemperature-

BasicconceptofindentationfracturetoughnessListofthetestedmaterialsMaterialTensiletestresultsKJCfromJ-testresultsEYSUTSnefUniformstrainSpecimenthicknessJCKJC(Avg.)Stdev.MPammkJ/m2MPa√m

1Carbon

steel(structure)SCM4207000723.349994.4880.1300.1680.066843.68106.160.342SK3207000315.100706.5270.2630.3560.180834.7688.8610.823SKS3207000434.900755.5020.2180.3140.160860.60118.175.784SKH51207000294.850784.3720.2590.1710.117814.5759.754.365SKD11207000342.800807.6870.2550.1180.099840.5298.376.836SUJ2207000404.300821.6590.2400.3330.161854.38113.8713.037S45C207000338.473727.8050.2690.2730.14715144.61181.325.078SCM21207000288.752579.3490.2230.2980.14215339.98281.3712.039SS400207000259.399497.0340.2380.3800.18220423.05310.210.0510SKD61207000377.415765.8150.2350.3100.14220571.61360.583.0211LowTemp.pipelineA106207000304.523583.1540.2170.3030.15813.5304.56263.0313.5812Cr-Mo(boilertube)A387G22207000519.350689.0200.1420.2490.08516518.58343.1418.1213API(petroleumpipeline)X65207000466.913650.8750.1690.3500.14914372.91291.187.9914X100207000598.560918.0720.1410.2510.08919548.24352.8019.0715X120207000745.8631022.9690.1300.2000.05416687.95395.529.2516StainlesssteelSUS403207000335.277671.5270.2120.3600.15413332.40274.9810.9217SUS420J2207000398.468797.6890.2070.2900.1248103.87155.2910.5818SUS440207000329.900820.7670.2560.2150.118826.3385.020.1219SUS304207000285.6851138.3780.3590.7740.49320537.13349.2717.0520SUS304L207000258.8161164.7280.4020.6540.42720666.29389.2111.0421SUS347207000244.863999.4890.3690.6440.41623591.39366.746.4322SUS321207000252.4021039.9660.3730.7240.47122499.02336.912.6723Al-alloyAl202470000459.100669.3990.1520.1650.128848.2064.077.5324Al707570000517.700621.8130.0800.1360.050817.2436.969.1025Cu-alloyC62400120000433.206842.9450.259-0.06694.8325.610.3526InCu120000160.025480.8550.3280.4830.37117187.25156.8515.1527Ni-alloyAlloy20207000348.337762.1780.2350.3790.20717453.21321.08-

28Ti-alloyTi-6Al-4V110000937.1281099.8150.080-0.086990.16113.6211.4329Ti-6Al-6V-2Sn1100001009.2301172.5600.076-0.105939.0072.243.1230Ti-5Al-2.5Sn110000885.5691038.0130.066-0.096961.5686.635.7331Ti-10Al-2Fe-3Al1100001163.3181257.3320.096-0.027994.0796.5917.33Comparingbetweenconventionalfracturetoughnessresultsand

instrumentedindentationtestingresultsfor31metalsTestingconditionsIndenterIndenterradiusControllingmethodWCsphericalindenter250umMax.depthcontrolEquipmentAISSystemMax.indentationdepth150umZeroindex0.06kgfSurfaceroughnessSandpaper#2000+20%-20%KJCResultsKJCfromIIT(MPa√m)KJCfromJc(MPa√m)Brittle

fracture

modelDuctile

fracture

modelKJCResultsBrittlematerialsDuctilematerialsDuctileMaterialKJCfromJ-testKJCfromIITKJC(Avg.)Stdev.KJC(Avg.)Stdev.MPa√mMPa√mCarbon

steel(structure)SCM21281.3712.03256.504.73SS400310.210.05235.4515.18SKD61360.583.02316.4710.96LowTemp.PipelineA106263.0313.58242.6011.01Cr-Mo(boilertube)A387G22343.1418.12273.6311.18API(petroleumpipeline)X65291.187.99273.336.03X100352.8019.07330.7513.57X120395.529.25448.105.54StainlesssteelSUS403274.9810.92251.263.86SUS304349.2717.05373.3821.34SUS304L389.2111.04398.4733.71SUS347366.746.43326.2811.94SUS321336.912.67324.2215.87Ni-alloyAlloy20321.08-292.885.53BrittleMaterialKJCfromJ-testKJCfromIITKJC(Avg.)Stdev.KJC(Avg.)Stdev.MPa√mMPa√mCarbon

steel(structure)SCM4106.160.3490.876.62SK388.8610.8289.963.49SKS3118.175.78110.683.10SKH5159.754.3690.1310.99SKD1198.376.8389.827.96SUJ2113.8713.03103.1914.21S45C181.325.07165.809.49StainlesssteelSUS420J2155.2910.58156.817.94SUS44085.020.1294.779.75Al-alloyAl202464.077.5352.064.56Al707536.969.1043.873.30Cu-alloyC6240025.610.3516.82-InCu156.8515.15160.376.06Ti-alloyTi-6Al-4V113.6211.43108.3315.47Ti-6Al-6V-2Sn72.243.1250.076.96Ti-5Al-2.5Sn86.635.7392.2110.47Ti-10Al-2Fe-3Al96.5917.3375.1915.14LowTemperatureChamberSystemEvaluationoffracturetoughnesswithchangingtemperatureMeasurementoffracturetoughness

atlowtemperatureAnalysisofsubzerotemperature

usingASTME1921[Application]ChamberSize(WxDxH)410x300x160(mm)CoolingelementLiquidnitrogenCircumstancesoftestVacuum,isolationMinimumTemp.-160oC(-256oF)Coolingrate~40oC/min(~40oF/min)[Specifications]ChamberControllerAISSystemChamberCharpyV-notchsampleRelationbetweenCVNresultsandIITtoughnessresults-Material:2.25Cr1MoVsteel(Weldments)-Testtemperature;RTand-29oCApplicationsatlowtemperatureApplicationsatlowtemperature-MasterCurve○:KJCfromIIT▲:KJCfromJ-TestSpecimeninformationandtestingconditionsChemicalcomposition(wt.%)