仪器压痕法断裂韧性检测方法.ppt
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1、Fast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityEvaluation of Fracture Toughness of MaterialsUsing Instrumented Indentation Technique:Ductile/Brittle Fracture Models2013.08.30.Won Je Jo Introduction Indentation Fracture Toughness Models-Brittle fracture mo
2、del-Ductile fracture model Verification of the Models-Comparison between fracture test results and IIT results-Applications at low temperature Basic concept of indentation fracture toughnessFast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityFracture testCrack
3、 propagation and fractureIndenterIITNo crack and no fractureIssue of indentation fracture toughnessWhat is a correlation between fracture test and IIT?In the case of metals,Fast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityConstraint effectahead of a crack t
4、ipPlastic region constrained by elastic regionbeneath an indenterSimilar constraint effectSimilar constraint effectFast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityR=250mIndenterMaterial:API X70loadingConstraint effect2.1 3.22.3 3.0Triaxiality of crack tip
5、Triaxiality of indentationSENBSENBIndentationIndentationFast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityIndentation fracture toughnessAnalogous situationFast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityEnergy conc
6、ept=Required energy for crack propagationEquivalent fracture energy in IndentationAnalysis of indentation processFast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityIndentation processFormation of a plastic zone to the surfaceFast&Precise SolutionsFast&Precise
7、 Solutions for Quality&Reliability for Quality&ReliabilityFormation 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
8、 energyh*c/ahh*Fast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityBrittle materialsDuctile materialsFracturesurfaceDeformationRelatively little or no deformationLarge plastic deformationCriterionStress controlledcritical fracture stress at the crack tip(sf)St
9、rain controlledcritical fracture strain at the crack tip(ef)Formation offracture energyWhen stress reached critical fracture stressWhen strain reached critical fracture strainFracture BehaviorBrittle Fracture ModelDuctile Fracture ModelFast&Precise SolutionsFast&Precise Solutions for Quality&Reliabi
10、lity for Quality&ReliabilityBrittle Fracture ModelFast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityCriterionCritical indentation depth(h*)rrCritical stress(pressure)at h*CriterionFast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quali
11、ty&ReliabilityAssumptionOnset of formation to a fully-developed plastic zone=Formation of Equivalent fracture energyFast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityApplication of indentation theoriesStep 1 Yielding right outside the contact areaFormation o
12、f a plastic zone to the surfaceStep 2Expansion of the plastic zoneFormation of fully-developed plastic zonecah*Fast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityHertz elastic contact theoryStress outside the contact area(r a)vWhen a radial stress at the edge
13、 of the contact area(r=a)satisfied yielding criterion By Von Mises yield criterionFast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityExpanding cavity model(E-P theory)Stress within plastic zone(a r c)vChange of the core pressure(r=a)until forming the fully-de
14、veloped plastic zoneby K.E.Puttick(1977)coreFast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityCriterion of equivalent fracture energyStep 1The total pressure required for equivalent fracture energy,Step 2Fast&Precise SolutionsFast&Precise Solutions for Quali
15、ty&Reliability for Quality&ReliabilityFracture toughness for brittle materiall Pm-h curvel Indentation load-depth curve-Mean contact pressure at each unloading depth(1)Indentation testing(6)Indentation fracture toughness(KJC)(2)Measuring ys&Determining Pmc-ys from analyzing L-h curve(3)Fitting Pm-h
16、curve-(4)Determining h*-Inserting determined Pmc into Pm-h curve(5)Equivalent fracture energy until h*Fast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityDuctile Fracture ModelFast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&Rel
17、iabilityCriterionCritical indentation depth(h*)rrCritical strain at h*CriterionFast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityCritical strain at h*CriterionAbsorbed strain energy until fracture strain=Toughness(tensile energy)Fast&Precise SolutionsFast&Pr
18、ecise Solutions for Quality&Reliability for Quality&ReliabilityAssumptionPeel and Frosyth,1973Plastic work done per unit areaPlastic work done per unit arear:the radius of the plastic zoneUT:plastic work done per unit volumeFor small scale yielding,Elastic energy released per unit areaElastic energy
19、 released per unit areaFast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityPlastic workMechanical metallurgy,G.E.DieterPlastic work done =Area Under the Stress-Strain CurvesR:flow stressef :engineering fracture strainFast&Precise SolutionsFast&Precise Solution
20、s for Quality&Reliability for Quality&ReliabilityMechanical parametersEstimation from indentation parametersPlastic zone sizeFracture strainMeasured parametersElastic propertiesvs.Plastic propertiesFunction of uniform strain Yield strength Ultimate tensile strength Elastic modulus Poissons ratio,n=0
21、.3Fracture toughnessrcefMeasured by indentation testFast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityPlastic zone size,rcPPlastic flowElastic constraintPlastic zoneA balance between plastic flowand elastic constraintDominant elastic constraintDominant plast
22、ic flow Small PZSLarge PZSResilienceResilienceFracture strain,efExperimental relation betweentrue uniform strain and engineering fracture strain,Fast&Precise SolutionsFast&Precise Solutions for Quality&Reliability for Quality&ReliabilityPlastic zone sizeFracture strainMeasured parametersFracture tou
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- 仪器 压痕 断裂韧性 检测 方法
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