STUDY OF THE INFLUENCE OF GEOMETRY AND PARTICLE SIZE ON THE DENSIFICATION AND COMPACTION MECHANICS OF UNIAXIALLY COLD COMPACTED RINGS

A standard SS-316L powder was sieved into three different particle-size ranges and uniaxially cold compacted to produce ring samples characterized by two different H/(Dext-Dint) ratios. The experiments were performed using an industrial press, continuously recording the forces and displacements applied on the die, core, and upper and lower punches. The measured data were used to study the densification mechanisms, and a new model describing the compaction mechanics of ring-shaped parts has been proposed and validated. The work investigates the influence of particle size and ring height on the densification phenomena and the compaction mechanics. No significant effect of ring height on the mean compaction pressure and the mean deformation was observed, while the influence on friction coefficients has been pointed out. A strong effect of particle size on densification/compaction phenomena has been highlighted: on increasing the particle size, a higher pressure was required to reach the same green density, and a larger amount of deformation was observed. The transition to prevailing plastic deformation occured at a lower relative density for a coarse particle size. Friction coefficients with die and core surfaces were lower for a coarse particle size. On increasing the particle size, the radial to axial stress transmission coefficient decreased.