MCE Ph.D. Thesis Seminar

Granular materials demonstrate complex behavior at multiple length scales. This talk will address three of these behaviors: the emergence of force chains at the grain-scale, the rate-strengthening nature of friction at the mesoscale, and flow at the macro-scale. First, I will discuss inverse problems for inferring inter-particle forces in experiments on granular materials. Inferred forces help to calibrate and validate numerical models and augment our understanding of granular materials in scenarios where existing models are not applicable. Second, I will discuss new friction laws for granular flows that explicitly incorporate grain-scale quantities. These friction laws paint a cause-and-effect relationship between changes in grain-scale quantities and friction. Discrete Element Method simulations will explore the evolution of these quantities to elucidate the rate-strengthening nature of friction. Finally, I will discuss a new method for modeling macro-scale flow of granular materials. The method combines a viscoplastic constitutive law for granular media with a Smoothed Particle Hydrodynamics (SPH) framework for capturing material flow and fragmentation. The viscoplastic constitutive law contains a strain-rate and pressure-dependent yield criterion derived from the mesoscale friction laws. Validation and example applications will be discussed.