The biaxial compaction of a square array of circular cylinders is studied u
sing slip-line field, upper bound and finite element methods. Densification
is assumed to occur by plastic deformation at the contacts. It is found th
at contact-contact interaction has a softening effect on the local indentat
ion pressure at each contact. The yield surfaces resulting from hydrostatic
and closed-die compaction are constructed at various stages of densificati
on: the size and shape of the yield surface depend upon the loading history
and upon the relative density of the compact. The finite element predictio
ns suggest the formation of a vertex at the loading point for the entire de
nsification process in the case of isostatic compaction. On the other hand,
a vertex at the loading point is formed only for a relative density D less
than or equal to 0.85 in the case of closed-die compaction. (C) 2000 Elsev
ier Science Ltd. All rights reserved.