仪器压痕法断裂韧性检测方法课件

1、仪器压痕法断裂韧性检测方法,Evaluation of Fracture Toughness of MaterialsUsing Instrumented Indentation Technique: Ductile/Brittle Fracture Models,2013. 08. 30,Won Je Jo,仪器压痕法断裂韧性检测方法,Contents,Introduction,Indentation Fracture Toughness Models,Brittle fracture model Ductile fracture model,Verification of the Mode

2、ls,Comparison between fracture test results and IIT results Applications at low temperature,Basic concept of indentation fracture toughness,仪器压痕法断裂韧性检测方法,Fracture test,Crack propagation and fracture,Indenter,IIT,No crack and no fracture,Issue of indentation fracture toughness,What is a correlation b

3、etween fracture test and IIT,In the case of metals,仪器压痕法断裂韧性检测方法,Constraint effect,ahead of a crack tip,Plastic region constrained by elastic region,beneath an indenter,Similar constraint effect,仪器压痕法断裂韧性检测方法,R=250m,Indenter,Material : API X70,loading,Constraint effect,2.3 3.0,Triaxiality of crack t

4、ip Triaxiality of indentation,仪器压痕法断裂韧性检测方法,Indentation fracture toughness,Analogous situation,仪器压痕法断裂韧性检测方法,Energy concept,Required energy for crack propagation,Equivalent fracture energy in Indentation,Analysis of indentation process,仪器压痕法断裂韧性检测方法,Indentation process,Formation of a plastic zone to

5、 the surface,仪器压痕法断裂韧性检测方法,Formation of a fully-developed plastic zone (c/a is constant,Expansion of plastic zone (c/a increase,c,a,c,a,Assumption,Onset of formation of a fully-developed plastic zone = Maximum strain energy beneath the indenter Formation of equivalent fracture energy,h,c/a,h,h,仪器压痕法

6、断裂韧性检测方法,Fracture Behavior,Brittle Fracture Model,Ductile Fracture Model,仪器压痕法断裂韧性检测方法,Brittle Fracture Model,仪器压痕法断裂韧性检测方法,Criterion,rr,Critical stress(pressure) at h,Criterion,仪器压痕法断裂韧性检测方法,Assumption,Onset of formation to a fully-developed plastic zone = Formation of Equivalent fracture energy,仪器

7、压痕法断裂韧性检测方法,Application of indentation theories,Step 1 Yielding right outside the contact area Formation of a plastic zone to the surface,Step 2 Expansion of the plastic zone Formation of fully-developed plastic zone,c,a,h,仪器压痕法断裂韧性检测方法,Hertz elastic contact theory,Stress outside the contact area (r

8、 a,When a radial stress at the edge of the contact area (r = a) satisfied yielding criterion,By Von Mises yield criterion,仪器压痕法断裂韧性检测方法,Expanding cavity model (E-P theory,Stress within plastic zone (a r c,Change of the core pressure (r = a) until forming the fully-developed plastic zone,by K.E. Putt

9、ick (1977,core,仪器压痕法断裂韧性检测方法,Criterion of equivalent fracture energy,Step 1,The total pressure required for equivalent fracture energy,Step 2,仪器压痕法断裂韧性检测方法,Fracture toughness for brittle material,Pm - h curve,Indentation load-depth curve,Mean contact pressure at each unloading depth,1) Indentation t

10、esting,6) Indentation fracture toughness (KJC,2) Measuring ys RT and -29oC,Applications at low temperature,仪器压痕法断裂韧性检测方法,Applications at low temperature - Master Curve,: KJC from IIT,: KJC from J-Test,Specimen information and testing conditions,Chemical composition of specimen,仪器压痕法断裂韧性检测方法,Applicat

11、ions at low temperature - Master Curve,: KJC from IIT,: KJC from J-Test,Reference : Bong-Sang Lee, Min-Chul Kim, Maan-Won Kim, Ji-Hyun Yoon, Jun-Hwa Hong, “Master curve techniques to evaluate an irradiation embrittlement of nuclear reactor pressure vessels for a long-term operation”, International Journal of Pressure Vessels and Piping 85 (2008