A Crystal Plasticity View of Powder Compaction

The cold compaction of an aggregate of powder is treated from the viewpoint of crystal plasticity theory. The contacts between particles are treated as compaction planes which yield under both normal and shear straining. The hardening of each plane represents both geometric and material hardening at the contacts between particles; the macroscopic tangent stiffness can be written in terms of the hardening rate for active compaction planes. During the early stages of compaction the contacts yield in an independent manner, which can be interpreted within the crystal context as independent hardening. The macroscopic yield surfaces for isostatic and closed die compaction are estimated for a uniform distribution of an orthogonal pair of compaction planes. A vertex forms at the loading point and significant anisotropy develops for closed die compaction.