Colloquium: Microscopic insights into the structure and stability of granular materials

Speaker

Dr. Carmen Lee (North Carolina State University)

Abstract

Dense granular materials, like piles of sand, coffee beans, or powders, often lie at the critical boundary between solid and liquid-like behaviour. When subjected to forces like gravity or external loading, these materials exhibit heterogeneous patterns of force transmission that appear as intricate force networks. However, at the large scale, the networks are not homogeneous and often have an associated structure that depends on the loading history of the material. As well, the force networks map out rigid and floppy subregions of the material. The inherent heterogeneity of any particulate material complicates the utility of taking system-wide averages and makes continuum modeling challenging to achieve. In my talk, I will show how photoelastic granular experiments provide a way to directly observe force networks, map the structure and stability of the material, and are an idealized material to aid in understanding other particulate matter, like cellular tissue, colloids, or foams.