Crack initiation and growth in 316LN stainless steel: Experiments and XFEM simulations

A methodology for computer simulation of ductile fracture in engineering structures using the eXtended Finite Element Method (XFEM) is presented. Crack initiation is modeled using an instability-based failure criterion derived from the micromechanics of void coalescence. The criterion depends on the state of stress at failure, strain hardening and the void volume fraction, whose evolution as a function of plastic strain is obtained using a physics-based void growth law. Material separation is modeled using the cohesive zone method, where cohesive surface elements are dynamically inserted into continuum elements that satisfy the failure criterion. The methodology is illustrated by comparing the model predictions with experimental data on uncracked and pre-cracked 316LN stainless steel specimens. It is shown that, using a set of parameters calibrated from standard tests, the model is able to quantitatively predict fracture in a variety of specimens. In contrast, widely used continuum damage models are unable to predict fracture in the different specimen types using a single set of material parameters.