APPLICATION OF A GRADIENT DUCTILE DAMAGE MODEL TO METAL FORMING PROCESSES INCLUDING CRACK PROPAGATION AND MESH

Summary. The entire process of ductile failure is modelled, from the initiation of damage to crack propagation. The microscopic material degradation mechanisms which trigger cracks are modelled by a softening elastoplastic behaviour. Mesh objec-tivity is ensured by a gradient enhancement. The two governing partial dierential equations, i.e. equilibrium and a nonlocal averaging equation, are solved in a stag-gered manner, which renders a relatively simple implementation in existing nite element codes. Adaptive remeshing fulls a threefold purpose: (i) allowing to model the geometry of discrete cracks; (ii) optimising the use of nite elements, so that ner elements are used in the regions of high strain localisation; (iii) preventing large element distortions. A number of metal forming simulations are shown which illustrate the main model features.