EXPERIMENTAL-TECHNIQUES FOR ANALYSIS OF DIE PRESSING AND EJECTION OF METAL-POWDER

The die pressing test is widely used to investigate the mechanical beh aviour of powders. However, analysis of the results may be problematic because of the effects of powder-wall friction and the analysis requi res measurements of the radial stress applied to the die. Two die pres sing devices, allowing continuous measurement of this stress during co mpaction (either directly or through the deformation of the die), are presented. From the results obtained for an iron powder, an analysis o f each step of the die pressing process (loading, unloading, and eject ion) is proposed. The three models derived in this manner provide esti mates of intrinsic properties of the material and of the powder-die fr iction coefficient. The validity of the analysis is discussed with ref erence to the results of finite element calculations.