Numerical simulation of metal powder die compaction with special consideration of cracking

Powder die compaction is modelled using the finite element method and a phe nomenological material model. The Drucker-Prager cap model is modified with the goal to describe the formation of cracks during powder transfer, compa ction, unloading, and ejection of the parts from the die. This is achieved by considering the cohesive strength and the cohesion slope, which characte rise the current strength of the powder compact in the Drucker-Prager model , as state dependent variables. Evolution equations are formulated for thes e variables, so that the strength increases by densification and decreases by forced shear deformation. Some of the parameters appearing in the evolut ion equations are determined from measured green strength values. An iron b ased powder (Distaloy AE) is used for the experiments. Examples are shown t o demonstrate that the density distribution can be calculated accurately as compared with an experiment, that cracking can be modelled at least qualit atively correctly, and that the compaction of complex 3D parts can be simul ated.