On the mechanics of cold die compaction for powder metallurgy

The main object of this paper is to present a theoretical model for the cold die compaction of powder materials based on the axisymmetric solution of large deformation. The model produces an expression relating the green density of the compact to the applied pressure. The analysis takes into account the internal (restricted movements) coefficient of friction between the particles and the container-compacted powder interface friction. Also, a modified analytical expression for the yield compression stress based on the internal coefficient of friction and the work-hardening of the powder was introduced in the analysis. Experiments were performed on cold die compaction of powder of different particles, having sizes between 45 and 150 mu m. Comparison between experimental and theoretical results demonstrated remarkable agreement for all the tested conditions. In addition, and for the purpose of verification of the present theory, other published experimental values were also compared and found to be in very good correlation with the predicted results. Other relevant parameters will also be discussed. (c) 2004 Elsevier B.V. All rights reserved.