The compaction of a random distribution of metal cylinders by the discreteelement method

The cold compaction of a 2D random distribution of metal circular cylinders has been investigated numerically by the discrete element method. Each cyl indrical particle is located by a node at its centre and the plastic indent ation of the contacts between neighbouring particles is represented by non- linear springs. The initial packing of the particles is generated by the ba llistic deposition method. Salient micromechanical features of closed die a nd isostatic powder compaction are elucidated for both frictionless and sti cking contacts. It is found that substantial rearrangement of frictionless particles takes place. leading to yield surfaces of similar shape but about half the size of that found for affine motion, as reported in [J. Mech. Ph ys. Solids 40 (1992) 1139 43 (1995) 1409; 47 (1999) 785]. An increase in th e level of inter-particle friction leads to a reduction in the degree of lo cal particle rearrangement: the relative displacement of particle centres i n the network is more closely represented by affine motion for the case of sticking contacts than frictionless contacts. The discrete element calculat ions suggest that the yield surfaces for sticking contacts are similar in s hape to those for frictionless particles, but are about double the size. (C ) 2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights r eserved.