BEM Implementation of a Quasistatic and Rate-independent Non-associative Model of Mixed-mode Interface-crack Growth

Abstract

The present authors and coworkers have recently developed a new physically and mathematically well justified and efficient approach for interface crack onset and propagation, implemented in finite and boundary element method (FEM and BEM) codes and applied to several problems of engineering interest. This approach borrows concepts from damage mechanics, such as the damage variable, from plasticity, as kinematic hardening, and from interface fracture mechanics, as fracture energy dependent on the fracture mode mixity. The computational implementation is based on recursive minimizations of a total energy functional, which can be computed by FEM and BEM. Global or specific local minimizations lead to different solution types, the energetic and stress driven solutions, respectively. In opposite to the associative models, where interface plasticity is explicitly taken into account by a plastic slip variable, applied to mixed-mode crack propagation problems by the present authors so far, it seems that non-associative models have the advantage of ending up at easier (e.g. smooth instead of non-smooth) and reduced (e.g. elimination of plasticity variable) minimization problems. An implementation of such a non-associative model in a collocation BEM code is presented and applied to an engineering problem of delamination.