Damage Evolution Modeling in Bulk Forming Processes

Abstract A mathematical formulation is presented for the analysis of metal forming operations which lead to accumulation of material damage by the nucleation and growth of voids. Two different approaches are introduced to model the accumulation of damage within the context of this formulation. Emphasis of the formulation is on the application of two state variable models to describe the strain hardening, rate-dependent plastic flow with plastic dilatancy. The numerical predictions have been compared with reported sheet drawing experiments. Good agreement between the numerical predictions and the experimental data demonstrates the success of the formulation. The application of the mathematical formulation in the design of manufacturing operations has been further demonstrated by studying the effect of die angle geometry, for a fixed thickness reduction, on the accumulation of material damage and on the evolution of the hardness.