[learn_more caption=”Göran Frenning “] Göran Frenning is Professor in Pharmaceutical physics at the Department of Pharmacy, Uppsala University, Sweden. Professor Frenning has a PhD in Engineering Science and has more than 10 years of experience from the pharmaceutical field, where he has conducted research related to powder technology and modelling of drug release processes.  [/learn_more]

Abstract

In the pharmaceutical sector, considerably efforts have during recent years been devoted to improved process understanding and control. Important insights into the behaviour of granular materials under various processing conditions have emerged from the application of particle-scale simulation tools, most notably the discrete element method (DEM). To model confined powder compaction with the DEM is nontrivial, however, at least at high relative densities, because each particle experiences multiple simultaneous contacts that cannot be considered as independent.  Important progress has been made recently, resulting in the formulation of nonlocal contact models, but the picture is still incomplete. In this presentation, a multi-scale strategy for simulation of confined powder compression is presented. First, experiments and simulations are used to determine the response of individual particles. To this end, an apparatus for triaxial compression of individual granules has been constructed. The finite element method (FEM) is used to determine the response of individual elastoplastic granules subjected to multiple simultaneous contacts. Second, the obtained knowledge is incorporated into contact models suitable for implementation in the DEM. The normal forces are expressed as products of the average contact pressure and the contact areas. Third, DEM simulations of confined compression of granular materials are performed, and the results are compared to experiments. The typical model systems are comprised of spherical mm-sized granules.