High Velocity Compaction of Powder, 1st Report

Abstract

This paper deals with a high velocity compaction process of metal powder. The powder is assumed to be homogeneous continuum which can be treated as an ideal fluid, and jump conditions at a shock known as the Rankine-Hugoniot equations are employed for the basic equations.As an example, copper powder is used here. This powder is uniformly packed in a die with a constant cross-section, and then its free surface is struck by a rigid body. An equation of state of the powder assumed by a static pressure-density relation, and the conservations of mass and momentum specify a motion of an element of the powder. Furthermore it is assumed that the elastic recovery of the powder can be neglected and that the pressure increases only at a shock front, and thereby the powder between the front and a fixed plate is always at rest and a particle velocity of the powder between the body and the front is always the same as that of the body. Then, the conservation of total momentum including the body is added to the above equations. These four equations determine the pressure p, the density q, the particle velocity of the powder v and the velocity of the frontNumerical results obtained showed that the assumptions used in this theory were satisfactory and copper powder compacted at high velocity impacts had uniform density if the friction of the powder at side plates can be neglected.