A study of stresses in powder compacted components during and after ejection

A finite strain finite element method is used to examine the residual stres ses in a cup-shaped powder compact. Two rate-independent strain hardening p orous material models are used: the combined material model (Fleck, N.A., K uhn, L.T., McMeeking, R.M., 1992a. J. Mech. Phys. Solids 40 (5), 1139-1162) and a material model which includes the dependency of inter-particle cohes ive strength (Fleck, N.A., 1995. J. Mech. Phys. Solids 43, 1409-1431). The residual stress state in the unloaded cup is highly dependent on the compac tion process and less dependent on the ejection route. The maximum principa l stress plotted during ejection shows that higher stresses are found durin g the ejection process than those found in the completely unloaded specimen . The degree of inter-particle cohesive strength has hardly any effect on t he porosity distributions in the compacts but it has a strong influence on the stress state in the cups before unloading. However, after unloading, th e stress states become quite similar in the two types of materials. (C) 200 1 Elsevier Science Ltd. All rights reserved.