Damage modelling in metal forming problems using an implicit non-local gradient model

A non-local gradient damage formulation, based on an improved Lemaitre damage model, is adopted in order to address the modelling of internal damage of the material in metal forming processes, like forging, or to describe processes in which fracture is a part of the process itself, as in sheet blanking or metal cutting. The damage model takes into account the effect of partial crack closure by affecting damage growth differently in compression or in tension. A non-local damage field is introduced, by means of a diffusion differential equation, dependent on a characteristic length parameter in order to avoid mesh size and orientation dependence of the model.