Application of a gradient ductile damage model to metal forming processes including crack propagation and mesh adaptivity

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 objectivity is ensured by a gradient enhancement. The two governing partial differential equations, i.e. equilibrium and a nonlocal averaging equation, are solved in a staggered manner, which renders a relatively simple implementation in existing finite element codes. Adaptive remeshing fulfils a threefold purpose: (i) allowing to model the geometry of discrete cracks; (ii) optimising the use of finite elements, so that finer 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