J-Integral Estimation With the Stiffness Gradient Method for Power Law Hardening Materials

Abstract

A simplified method for determining the J -integral for elastic-plastic conditions using the stiffness gradient method is described. Power law hardening material is shown to simplify the J -integral estimation, rendering elastic and fully plastic J solution terms. Numerical results are obtained for an interior complete circumferential crack in a pipe and compared to the analogous EPRI handbook solution. Because the stiffness gradient method is based on external displacement and forces, and not directly dependent on the stresses, it is sufficient to use relatively coarse finite element meshes to detemine the J -integral instead of highly refined and costly meshes required in most conventional J -integral computations.