Calculated Stress and Strain Conditions of Lubricated Potassium Chloride Powders during Die-Compression

Abstract

The stress and strain distributions in a compressed powder bed of potassium chloride lubricated with magnesium stearate were calculated on the basis of the theory of limiting equilibrium states specified by the Mohr criterion for the axially symmetrical problems and of the stress-strain relations. The slopes of yield locus and wall yield locus for the powder bed, which were required for the calculations, were 0.426 and 0.0516, respectively. The calculated results were compared with those for an unlubricated powder bed at P_U (the upper punch pressure)=10.0kg/cm². More uniform distributions on the boundary surfaces and within the powder bed appeared in the present lubricated system. The stress distributions became large on the upper and lower punch surfaces as P_U increased. A region of higher stress appeared within the powder bed even at P_U=10.0kg/cm², and was clearer at P_U=60.0kg/cm².