An experimental evaluation of discrete element simulations of confined powder compression using an extended truncated-sphere model

Confined compression of powders consisting of millimetre-sized granules was studied numerically with the discrete element method (DEM) and experimentally using a materials tester. A novel contact model was used, referred to as the extended truncated-sphere model, which is based on a geometrical analysis of the particle shape coupled with a contact pressure that varies with volumetric particle strain. The model accounts for plastic particle densification and utilises Voronoi cells to estimate the void space surrounding each particle. Simulations were performed both with and without an account of plastic particle densification, using experimentally estimated values of hardness and literature values of bulk moduli as input. An adequate agreement between simulations and experiments was obtained for beds of ductile particles, but the correspondence was less satisfactory for ductile-brittle ones. The results indicate that a residual porosity remained in the particles also at the highest applied pressures in both cases. It was concluded that the novel extended truncated-sphere model is suitable for and provides insight into the problem of simulating confined powder compression at large strains. However, reliable results will likely not be obtained for fragmenting particles unless a way be found to describe particle fracture.