Crack Nucleation and Branching in the eXtended Finite Element Method

The eXtended Finite Element Method (X-FEM) has proven to be a robust method for simulating crack propagation, but relatively little work has focused on the important problem of crack initiation or nucleation. In this work, we examine various options for nucleating cracks within a cohesive framework and the X-FEM. Attention is confined to shell problems. We discuss the details of the methods and their strengths and weaknesses. With the introduction of such nucleation algorithms, the need to model more complex crack growth topologies also arises. In particular, we examine algorithms for enabling crack branching, focusing on both the mechanics and element kinematic considerations. The results of various benchmark problems for the nucleation and branching algorithms are also presented and discussed.