Integration of an adaptive cohesive zone and continuum ductile fracture model to simulate crack propagation in steel structures

Abstract

Damage mechanics continuum criteria have been shown to provide an effective alternative to conventional fracture mechanics parameters to simulate ductile crack initiation in mild steel under large scale yielding and variable stress states. In this study, a damage mechanics initiation criterion, called the Stress Weighted Damage Model, is extended to simulate ductile crack propagation through an Adaptive Cohesive Zone model. The proposed approach regularizes the crack tip singularity using features of conventional cohesive zone methods, while adaptively updating the traction separation relationship to model crack propagation based on the continuum damage criterion. The proposed model is implemented in the finite element platform WARP3D and demonstrated using a set of fourteen coupon scale fracture experiments of two structural steels. The tests include Circumferentially Notched Tensile bars and sharp-cracked Compact Tension specimens, where the response is represented by load-deformation response and J-R curves, respectively. Comparisons with test results demonstrate that the combined Stress Weighted Damage Model and Adaptive Cohesive Zone approach can accurately simulate crack propagation with consistent mesh convergence. Examples are included to contrast the proposed model capabilities with a conventional (stress-based) Cohesive Zone model and the Gurson-Tvergaard model.