3-D ELASTIC-PLASTIC FINITE-ELEMENT ANALYSIS OF INTERFACE CRACKS UNDER MIXED-MODE LOAD

A three-dimensional finite element computation was performed for a through-edge cracked bimaterial steel specimen under mixed mode loadings in which the crack was lying on an interface between an elastic-plastic material and a perfectly rigid substratum. In order to take account of the average effect of microvoid nucleation and growth in the deformation, the modified Gurson's constitutive equation suggested by Tvergaard and Needleman was used. It was found that due to the interaction between the singularity along the crack front and that along the interface on the specimen surface, the distributions of stresses, plastic deformations, J-integral and void volume fraction in a bimaterial specimen were significantly different from those in a homogeneous specimen. Based an the numerical results on the distributions of void volume fraction and J-integral, the locations of fracture initiation in bimaterial and homogeneous specimens under mixed mode loadings are discussed.