Numerical modelling of cyclic plasticity and fatigue damage in cold-forging tools

Industrial cold-forging tools with complex geometry are very likely to be exposed to local plastic deformation near stress concentrating details. The accumulation of plastic deformation resulting from the cyclic loading conditions leads to fatigue damage and eventually to generation of a crack in the surface of the die. To study the effect of die prestressing on fatigue damage development, a plane strain finite element model of a cold-forging die is analysed. A complex material model, combining kinematic and isotropic hardening with continuum damage mechanics, is used to simulate the elastic–plastic material behaviour and damage development. Furthermore, a range of uncoupled damage measures are applied in the comparison of conventional and new prestressing concepts.