Crack closure behavior and crack propagation characteristic of FGH95 powder metallurgy superalloy

Plasticity-induced crack closure effect of compact tension (CT) specimen of FGH95 powder metallurgy superalloy was investigated by using finite element method. The stress distribution in crack surface was analyzed. The effects of three principal factors, the constitutive model, mesh density and stress ratio, on the crack closure behavior were studied, to further establish crack propagation life analysis model of CT specimens with considering crack closure, and to predict life. The results show that crack closure in elastic-perfectly plastic constitutive model appears more sensitive to grid cell than that in multi-linear kinematic hardening constitutive model. Crack closure trends to be stable with the number of crack tip elements in the plastic zone reach to 20. Crack closure decreases with the increase of stress ratio, and disappears as stress ratio reaches to 0.5. The revised life prediction model shows higher prediction accuracy than traditional model for CT specimens.