Particulate materials do not: have inherent strength and stiffness (like a solid); flow freely (like a liquid); or compress easily (like a gas). The unique combination of properties possessed by granular materials includes that they are: inherently multiphase, porous, and pervious; nonlinear and inelastic; their volume changes during shear; and strength and stiffness depend on confinement, strain rate, and stress path. Given these observations, particulate materials are effectively a fourth phase of matter – neither solid, liquid, nor gas. Granular materials are not always amenable to continuum descriptions of behavior, so in some cases a discrete approach is adopted for modeling.
This talk will provide an introduction to the discrete element method (DEM) for the simulation of the mechanical behavior of granular materials. In DEM modeling, every grain in an assembly is modeled individually and simulation involves solution of Newton’s equations of motion for every particle at every time step. After an introduction of modeling basics and a brief discussion of particle-continuum duality, example applications will be presented. These will include some combination of bio-cementation of liquefiable sands, powder processing, thermally-induced mechanical shakedown, percolation thresholds, and localization of strains during shear.