2007

Abstract:

Granular materials are agglomerates of particles (10 microns to 10 meters) which interact with one another solely via dissipative contacts. These materials have practically zero temperature on account of the dissipative inter-particle interactions coupled with the particle size. The properties of these agglomerates depend upon their density and the degree of mechanical excitation; under specific conditions, these materials can be in the solid or fluid phase. I will be presenting my numerical investigations (using Discrete Element Method (DEM) techniques) on the packings of dense granular media generated by pouring and constant strain uni-axial compression. The systems of interest are motivated and developed by X-ray microtomography scans (X. Fu, et al. Powder Technology 2006) of pharmaceutical excipient compacts. I will be discussing the effect of substrate templating (Dutt, et al. Europhys. Letts. 2007) and particle size dispersity (Dutt, et al., in preparation) on the microstructure of these dense packings, and the macroscopic response to strain. I will link the porosity and the internal packing structure by the use of a dynamically tesselating algorithm (Benedict, et al. Physica A 2007) which calculates the pore network in dense particulate systems. In addition, I will be presenting some predictions of the macroscopic properties of excipient mixtures from investigations of the material microstructure. Finally, I will discuss some efforts in modeling pharmaceutical powders by using a combination of DEM numerical experiments and X-ray microtomography imaging.