Abstract
The effects of tool stiffness on powder die compaction process of multi-step parts have been investigated by performing FEM
analysis using Drucker-Prager CAP model as constitutive equation for granular materials. The material parameters of atomized
iron and ferrite powders were validated by comparing the results of uniaxial compaction tests with measurement die system.
The influence of punch spring back during unloading and ejection was focused to discuss occurrence of shear failure on powder
compact. FEM analysis for inner flange shape with different tool rigidity has been carried out. DPC model with measured materials
parameters simulates proper densification behavior but some deviation at residual stress especially for ferrite powder. Results of
analysis during and after unloading stage shows that inhomogeneous elastic recovery from tools leads to principal strain distribution
occurrence and shear stress concentration at ejection stage. Moreover, it was found that elastic recovery of lower punch promotes
inhomogeneity of residual stress especially for thinner rim shape.
