The effect of punch velocity on the compaction of a variety of materials.

The effect of punch velocity over the range 0.033-400 mms-1 on the compaction of a variety of materials has been studied using constants derived from the Heckel equation as criteria to describe their behaviour. For materials known to deform plastically, e.g. maize starch and polymeric materials, there was an increase in the yield pressure with punch velocity attributable to a change either from ductile to brittle behaviour or a reduction in the amount of plastic deformation due to the time dependent nature of plastic flow. For materials known to consolidate by fragmentation, e.g. magnesium and calcium carbonates, there was no change in yield pressure with increasing punch velocity. The data has been analysed in terms of the strain rate sensitivity of the materials calculated from their yield pressure at low and high punch velocities.