Extended finite element method for computation of mixed-mode stress intensity factors in three dimensions

A three-dimensional domain integral method for extracting mixed-mode stress intensity factors is described in detail. The method is based on the extended finite element method, which does not force the discontinuities to be in conformity with the mesh. In order to compute the pointwise stress intensity factors along the crack front, the domain integrals are evaluated as a post-processing step. As the crack surface is expressed by the level set method, no explicit meshing of the crack geometry emerges on the crack front. This makes difficult the domain integral. An independent grid of hexahedral cells around the crack front needs to be constructed as the virtual extension domain for accomplishing the domain integral. To assess the accuracy of the approach, a typical example of the mixed-mode crack is discussed. The results are found to be in good agreement with analytic and benchmark solutions.