XFEM-based element subscale refinement for detailed representation of crack propagation in large-scale analyses

In the present paper, we address the delicate balance between computational efficiency and level of detailing at the modelling of ductile fracture in thin-walled structures. To represent the fine-scale nature of the ductile process, we propose a new extended finite element method-based enrichment of the displacement field to allow for crack tips that end or kink within an element. The idea is to refine the crack tip element locally in a way such that the macroscale node connectivity is unaltered. This allows for a better representation of the discontinuous kinematics without affecting the macroscale solution procedure, which would be a direct consequence of a regular mesh refinement. The method is first presented in a general 3D setting, and thereafter, it is specialised to shell theory for the modelling of crack propagation in thin-walled structures. The paper is concluded by a number of representative examples showing the accuracy of the method. We conclude that the ideas proposed in the paper enhance the current methodology for the analysis of ductile fracture of thin-walled large-scale structures under high strain rates.