J estimation for shallow semi‐elliptical surface cracks in wide plates under pure bending

Abstract

Three‐dimensional finite element models have been used to predict the J versus applied strain behaviour of shallow semi‐elliptical surface cracks in wide steel plates. These models were loaded in pure bending up to fully plastic conditions that produced maximum strains remote from the crack of 10 times the yield strain. This study examined cracks with a crack depth to plate thickness ratio (a/t) in the range 0.05–0.15, and crack depth to crack half‐length ratio (a/c) from 0.2 to 0.57, in elastic‐hardening materials as well as those with a yield plateau before strain‐hardening. The results were found to differ significantly from those obtained from plane strain analyses, and a J estimation scheme was developed from the three‐dimensional results. Comparisons between the results obtained in this work and the J predictions provided by existing defect assessment methods show that the proposed equations are a significant improvement when large strains are likely.