Modelling and simulation of metal powder pressing

Abstract: The pressing of hard metal components was analysed with numerical methods. The aim was to calculate the density distribution and the springback during unloading. This thesis concentrated on the following parts; constitutive modelling, explicit versus implicit time integration schemes and contact constraint methods. Three constitutive models for the simulation of the mechanical material behaviour of hard metal powder were evaluated. The models were cap plasticity, multisurface plasticity and endochronic plasticity. The compaction of powder specimen was simulated assuming quasi-static conditions. The method of using explicit time integration of the equations of motion was compared with a traditional method employing implicit time integration. The results show that an explicit code is advantageous in terms of development potential, solution time and ease of use. Alternative constraint methods were evaluated when modelling the contact between powder and tool. A contact constraint method with friction based on direct integration of the equations of the contact interface was proposed. Two specific powder metallurgical parts, a highway engineering tip and a plate for testing crack sensibility, were selected for the analyses. The calculated density distributions were qualitatively in good agreement with experimental results. The springback obtained in the numerical simulation of unloading and ejection processes was in good agreement with measured values.