Numerical Investigation on Behavior of the J-Integral Range ΔJ of a Fatigue Crack Emanating from Notches

Abstract

In previous papers, the authors discussed the J-integral range, ΔJ, evaluated by the path-integral and showed that ΔJ was a good parameter for characterizing the crack tip stress and strain fields under elastic-plastic conditions. In this study, finite-element simulations of fatigue crack growth at notches in a plate under uniaxial stress were conducted to examine the applicability of ΔJ to short fatigue cracks emanating from notches. It was found that Δl-values evaluated by the path-integral were almost path-independent when the minimum-load level or the crack-opening level was selected as a reference level for the evaluation. The value of ΔJ evaluated based on the crack-opening level correlated well with the crack-tip-opening displacement, while ΔJ based on the minimum-load level and the effective stress intensity range ΔK_eff did not. Crack closure was mainly responsible for the initial decrease in ΔJ-value and the deceleration of crack growth rates of short cracks emanating from notches.