Some uses of n<inf>a</inf> and K<inf>a</inf> in the prediction of cold extrusion forces of sintered powder metallurgical preforms

Mathematical expressions have been derived for relating the values of apparent strength coefficient Ka (in N/mm2) and strain hardening exponent na to preform density ρ{variant}0, based on axial ring compression tests. These equations are consulted for prediction of cold hooker extrusion forces for P/M preforms of various starting preform densities, ρ{variant}0. Experimental values of extrusion forces are compared with those predicted. Such analysis demonstrates the usefulness of the generated Ka, na against ρ{variant}0 equations to avoid elaborate experimentation on the extrusion. Besides, the analysis suggests that the void closure is persistent till the theoretical density and if corrections are applied for force, theory and experiment agree well. © 1988.