Constitutive model for powders with characterisation of low pressure region of yield surface

Abstract

Numerical simulations of manufacturing processes rely on material characterisation. This highlights the need for a close combination of experimental and numerical work to model cold die powder compaction. Based on a previous experimental work by the authors, this document shows how the data collected can be used to formulate a constitutive model reflecting the material behaviour in a broad range of conditions. A plasticity model based on pressure and deviatoric stress was chosen. Particular attention was given to the definition of the yield properties under low pressure levels. This choice was motivated by the previous review of experimental techniques for powder characterisation and, in contrast with popular models which focus on the behaviour of the powder in conditions close to idealised frictionless uniaxial compaction, the updated model achieves a very good agreement with out of die tests for two different materials while retaining a single equation formulation for the yield surface.