Finite element calculation of applied J-integral for cracked ship structural details

Abstract

Finite-element (FE) analysis was used to calculate the applied J-integral ( J) as a function of applied displacement for cracked full-scale test specimens which are representative of ship structural components. The specimens were welded from relatively thin (9 mm) HSLA80 (ASTM A710) and EH36 (ASTM A131) steel plates. For relatively simple CCT panels, the J calculated with FE analysis compared favorably with solutions published in the literature. Estimation schemes based on the reference stress method did not work well for the fully plastic conditions with these low-strain-hardening materials. A practical and simple model for estimating applied J was proposed which gives acceptable results. It was found that the applied J vs displacement for shell cracks bridged by stiffeners or girders can be calculated from an idealized CCT model incorporating all of the sections as if they were coplanar. The FE-calculated J was used, together with a J– R curve which was measured on small compact specimens, to model ductile crack extension.