1、Evaluation of Fracture Toughness of MaterialsUsing Instrumented Indentation Technique:Ductile/Brittle Fracture Models2013.08.30.Won Je Jo Introduction Indentation Fracture Toughness Models-Brittle fracture model-Ductile fracture model Verification of the Models-Comparison between fracture test resul
2、ts and IIT results-Applications at low temperature Basic concept of indentation fracture toughnessFracture testCrack propagation and fractureIndenterIITNo crack and no fractureIssue of indentation fracture toughnessWhat is a correlation between fracture test and IIT?In the case of metals,Constraint
3、effectahead of a crack tipPlastic region constrained by elastic regionbeneath an indenterR=250mIndenterMaterial:API X70loadingConstraint effect0.00.10.20.30.40.50.601234563.0-y=3.011771-exp-4.57486(x+0.31229)tmaxV/Vmax0.00.10.20.30.40.50.601234563.2-y=3.298311-exp-3.65099(x+0.27357)tmaxhmax/R2.1 3.2
4、2.3 3.0Triaxiality of crack tip Triaxiality of indentationIndentation fracture toughness)1(2EJKCJCAnalogous situation?JCKEnergy concept)1(2EJKCJCCJ=Required energy for crack propagationEquivalent fracture energy in IndentationAnalysis of indentation processIndentation processFormation of a plastic z
5、one to the surfaceFormation of a fully-developed plastic zone (c/a is constant)Expansion of plastic zone(c/a increase)cacaAssumptionOnset of formation of a fully-developed plastic zone=Maximum strain energy beneath the indenter Formation of equivalent fracture energyh*c/ahh*Brittle materialsDuctile
6、materialsFracturesurfaceDeformationRelatively little or no deformationLarge plastic deformationCriterionStress controlledcritical fracture stress at the crack tip(sf)Strain controlledcritical fracture strain at the crack tip(ef)Formation offracture energyWhen stress reached critical fracture stressW
7、hen strain reached critical fracture strainFracture BehaviorBrittle Fracture ModelDuctile Fracture ModelBrittle Fracture ModelCriterionL(kgf)hmax(m)Critical indentation depth(h*)cmmpp rrCritical stress(pressure)at h*CriterionAssumptionOnset of formation to a fully-developed plastic zone=Formation of
8、 Equivalent fracture energydtdctime sizezone plastic finalexpansionofRateconstant/acdtdadtdcexpansion core of rate;dtdazone plastic developed-fullyApplication of indentation theoriesStep 1 Yielding right outside the contact areaFormation of a plastic zone to the surfaceeorycontact th elastic HertzSt
9、ep 2Expansion of the plastic zoneFormation of fully-developed plastic zone theory)plastic-(elastic modelcavity Expandingcah*Hertz elastic contact theoryStress outside the contact area(r a)m22rpr2a)21(ss0zsv When a radial stress at the edge of the contact area(r=a)satisfied yielding criterionmrp221s
10、By Von Mises yield criterionysymCps1Expanding cavity model(E-P theory)Stress within plastic zone(a r c)rips31)ln(2rcyyssss32)ln(2rcyrssysiysrpacsssln232v Change of the core pressure(r=a)until forming the fully-developed plastic zone1ac2Cacby K.E.Puttick(1977)impp ysiacpsln232coreCriterion of equival
11、ent fracture energyStep 1ysfcmCpsmymcmpppcmpThe total pressure required for equivalent fracture energy,Step 2iymppFracture toughness for brittle material020406080050010001500 PcmIndentation depth(m)h*Indentation mean pressure(kgf/m2)1(2EwKfJCl Pm-h curve0204060801001201401600102030405060L(kgf)hmax(m
12、)l Indentation load-depth curve2cmaxmaLp-Mean contact pressure at each unloading depth*0hcfdhALw(1)Indentation testing(6)Indentation fracture toughness(KJC)(2)Measuring ys&Determining Pmc-ys from analyzing L-h curve(3)Fitting Pm-h curveysfcmCps-(4)Determining h*-Inserting determined Pmc into Pm-h cu
13、rve(5)Equivalent fracture energy until h*Ductile Fracture ModelCriterionL(kgf)hmax(m)Critical indentation depth(h*)crreerrCritical strain at h*CriterionCritical strain at h*Criterion tensionuniaxialin strain fracture ceAbsorbed strain energy until fracture strain=Toughness(tensile energy)AssumptionE
14、lastic energy released due to the crack growth is equal to the amount of plastic work ahead of the crack tip.JEKG221Peel and Frosyth,1973TpUrW 2r:the radius of the plastic zoneUT:plastic work done per unit volumeFor small scale yielding,)1(2)1()1(222EUrEWEJKTcpCJCPlastic work)1(22EUrKTcJCMechanical
15、metallurgy,G.E.DieterfRfYSUTSTeeUsss21Plastic work done =Area Under the Stress-Strain Curve)1(Eer2K2fRcJCssR:flow stressef :engineering fracture strainMechanical parameters)1(Eer2K2fRcJCsEstimation from indentation parametersPlastic zone sizeFracture strainMeasured parametersElastic propertiesvs.Pla
16、stic propertiesFunction of uniform strain Yield strength Ultimate tensile strength Elastic modulus Poissons ratio,=0.3Fracture toughnessrcefMeasured by indentation testPlastic zone size,rcPPlastic flowElastic constraintPlastic zoneA balance between plastic flowand elastic constraintDominant elastic
17、constraintDominant plastic flow Small PZSLarge PZSEUysR22sFracture strain,efuffeeExperimental relation betweentrue uniform strain and engineering fracture strainRcUfr,)1(Eer2K2fRcJCsPlastic zone sizeFracture strainMeasured parametersFracture toughnessRcUfr uffeeFracture toughness for ductile materia
18、l21)()(esEfUfKuRRJCs,ER Introduction Indentation Fracture Toughness Models-Brittle fracture model-Ductile fracture model Verification of the Models-Comparison between fracture test results and IIT results-Applications at low temperature-Basic concept of indentation fracture toughnessList of the test
19、ed materialsMaterialTensile test resultsKJC from J-test resultsE YSUTSnefUniform strainSpecimen thicknessJCKJC(Avg.)Stdev.MPammkJ/m2MPam1Carbonsteel(structure)SCM4 207000723.349 994.488 0.130 0.168 0.066 843.68106.160.342SK3 207000315.100 706.527 0.263 0.356 0.180 834.7688.8610.823SKS3 207000434.900
20、 755.502 0.218 0.314 0.160 860.60118.175.784SKH51 207000294.850 784.372 0.259 0.171 0.117 814.5759.754.365SKD11 207000342.800 807.687 0.255 0.118 0.099 840.5298.376.836SUJ2 207000404.300 821.659 0.240 0.333 0.161 854.38113.8713.037S45C207000338.473 727.805 0.269 0.273 0.147 15144.61181.325.078SCM212
21、07000288.752 579.349 0.223 0.298 0.142 15339.98281.3712.039SS400207000259.399 497.034 0.238 0.380 0.182 20423.05310.210.0510SKD61207000377.415 765.815 0.235 0.310 0.142 20571.61360.583.0211Low Temp.pipelineA106207000304.523 583.154 0.217 0.303 0.158 13.5304.56263.0313.5812Cr-Mo(boiler tube)A387 G222
22、07000519.350 689.020 0.142 0.249 0.085 16518.58343.1418.1213API(petroleumpipeline)X65207000466.913 650.875 0.169 0.350 0.149 14372.91291.187.9914X100207000598.560 918.072 0.141 0.251 0.089 19548.24352.8019.0715X120207000745.863 1022.969 0.130 0.200 0.054 16687.95395.529.2516StainlesssteelSUS40320700
23、0335.277 671.527 0.212 0.360 0.154 13332.40274.9810.9217SUS420J2207000398.468 797.689 0.207 0.290 0.124 8103.87155.2910.5818SUS440 207000329.900 820.767 0.256 0.215 0.118 826.3385.020.1219SUS304207000285.685 1138.378 0.359 0.774 0.493 20537.13349.2717.0520SUS304L207000258.816 1164.728 0.402 0.654 0.
24、427 20666.29389.2111.0421SUS347207000244.863 999.489 0.369 0.644 0.416 23591.39366.746.4322SUS321207000252.402 1039.966 0.373 0.724 0.471 22499.02336.912.6723Al-alloyAl2024 70000459.100 669.399 0.152 0.165 0.128 848.2064.077.5324Al7075 70000517.700 621.813 0.080 0.136 0.050 817.2436.969.1025Cu-alloy
25、C62400120000433.206 842.945 0.259-0.066 94.8325.610.35 26InCu120000160.025 480.855 0.328 0.483 0.371 17187.25156.8515.1527Ni-alloyAlloy20207000348.337 762.178 0.235 0.379 0.207 17453.21321.08-28Ti-alloyTi-6Al-4V110000937.128 1099.815 0.080-0.086 990.16 113.62 11.43 29Ti-6Al-6V-2Sn1100001009.230 1172
26、.560 0.076-0.105 939.00 72.24 3.1230Ti-5Al-2.5Sn110000885.569 1038.013 0.066-0.096 961.56 86.63 5.73 31Ti-10Al-2Fe-3Al1100001163.318 1257.332 0.096-0.027 994.07 96.5917.33 Testing conditionsIndenterIndenter radiusControlling methodWC spherical indenter250 umMax.depth controlEquipmentAIS SystemMax.in
27、dentationdepth150 umZero index0.06 kgfSurface roughnessSand paper#2000050100150200250300350400450500050100150200250300350400450500X65SUS403InCuX100X120SCM21SS400SKD61A106A387-G22Alloy20304304L347321S45CSUS420J2SCM4SKS3SUS440SKH51SUJ2SKD11SK3Ti-10-2-3Ti-6-4Ti-6-6-2Ti-5-2.5C62400Al2024Al7075X120304LA1
28、06SS400X65SCM21403A387-G22SKD61347420J2S45CInCu Ti-10-2-3Ti-6-4Ti-5-2.5Ti-6-6-2Al2024Al7075C62400SK3SCM4SKD11440SUJ2SKS3SKH51321X100Alloy20304+20%-20%KJC ResultsKJC from IIT(MPam)KJC from Jc(MPam)BrittlefracturemodelDuctilefracturemodelKJC ResultsDuctileMaterial KJC from J-testKJC from IITKJC(Avg.)S
29、tdev.KJC(Avg.)Stdev.MPamMPamCarbonsteel(structure)SCM21281.3712.03256.504.73SS400310.210.05235.4515.18SKD61360.583.02316.4710.96Low Temp.PipelineA106263.0313.58242.6011.01Cr-Mo(boiler tube)A387 G22343.1418.12273.6311.18API(petroleumpipeline)X65291.187.99273.336.03X100352.8019.07330.7513.57X120395.52
30、9.25448.105.54StainlesssteelSUS403274.9810.92251.263.86SUS304349.2717.05373.3821.34SUS304L389.2111.04398.4733.71SUS347366.746.43326.2811.94SUS321336.912.67324.2215.87Ni-alloyAlloy20321.08-292.885.53BrittleMaterialKJC from J-testKJC from IITKJC(Avg.)Stdev.KJC(Avg.)Stdev.MPamMPamCarbonsteel(structure)
31、SCM4 106.160.3490.876.62SK3 88.8610.8289.963.49SKS3 118.175.78110.683.10SKH51 59.754.3690.1310.99SKD11 98.376.8389.827.96SUJ2 113.8713.03103.1914.21S45C181.325.07165.809.49StainlesssteelSUS420J2155.2910.58156.817.94SUS440 85.020.1294.779.75Al-alloyAl2024 64.077.5352.064.56Al7075 36.969.1043.873.30Cu
32、-alloyC6240025.610.35 16.82-InCu156.8515.15160.376.06Ti-alloyTi-6Al-4V113.62 11.43 108.3315.47Ti-6Al-6V-2Sn72.24 3.1250.076.96Ti-5Al-2.5Sn86.63 5.73 92.2110.47Ti-10Al-2Fe-3Al96.5917.33 75.1915.14Low Temperature Chamber System Evaluation of fracture toughness with changing temperature Measurement of
33、fracture toughness at low temperature Analysis of subzero temperature using ASTM E1921Application Chamber Size(WxDxH)410 x 300 x 160(mm)Cooling elementLiquid nitrogen Circumstances of testVacuum,isolation Minimum Temp.-160 oC(-256 oF)Cooling rate 40 oC/min (40 oF/min)SpecificationsChamber Controller
34、AIS SystemChamberCharpy V-notch sampleT 1_1T 1_2T 2_1T 2_2020406080100120140160180 IIT CharpyFT,KJC from IIT(MPam0.5)020406080100120140At Room TemperatureCVN(J)T 1_1T 1_2T 2_1T 2_2020406080100120140160180FT,KJC from IIT(MPam0.5)IIT Charpy020406080100120140At-29 oCCVN(J)Relation between CVN results a
35、nd IIT toughness results-Material:2.25Cr1MoV steel(Weldments)-Test temperature;RT and-29oCApplications at low temperatureApplications at low temperature-Master Curve:KJC from IIT:KJC from J-Test Specimen information and testing conditionsChemical composition(wt.%)C Si Mn P S Ni 0.21 0.24 1.36 0.007
36、0.002 0.92 Cr Mo Al Cu V 0.21 0.49 0.022 0.03 0.005 Chemical composition of specimenMaterialSA508-3,ID:GS880SpecimenCompact tension and precracked CVNUseNuclear reactor pressure vesselTemperature range(about10 Interval)-110-20Fracture toughness testingASTM E1920-200-150-100-50050050100150200250FMCG,
37、KAERIGS880,PCVN KJC,1T (MPa-m0.5)Temperature(oC)T0=-63.5oC Median 5,95%Tolerance boundApplications at low temperature-Master Curve:KJC from IIT:KJC from J-TestReference:Bong-Sang Lee,Min-Chul Kim,Maan-Won Kim,Ji-Hyun Yoon,Jun-Hwa Hong,“Master curve techniques to evaluate an irradiation embrittlement
38、 of nuclear reactor pressure vessels for a long-term operation”,International Journal of Pressure Vessels and Piping 85(2008)593599 Specimen information and testing conditionsChemical composition(wt.%)C Si Mn P S Ni 0.21 0.24 1.36 0.007 0.002 0.92 Cr Mo Al Cu V 0.21 0.49 0.022 0.03 0.005 Chemical co
39、mposition of specimenMaterialSA508-3,ID:CS50SpecimenCompact tension and precracked CVNUseNuclear reactor pressure vesselTemperature range(about10 Interval)-110-20Fracture toughness testingASTM E1920-200-150-100-50050050100150200250FMCG,KAERICS50,PCVN KJC,1T (MPa-m0.5)Temperature(oC)T0=-26.5oC Median 5,95%Tolerance bound
