Numerical simulations of the incremental responses of idealized granular materials

Herein we investigate the incremental structure of several constitutive theories-elasticity, single and multiple mechanisms elastoplasticity, and vertex plasticity-in the case of idealized granular materials. Based on numerical simulations, we determine the incremental strains that result from a series of stress increments with an identical amplitude but different directions. Idealized granular materials are found to exhibit an incrementally piecewise-linear behavior that is described by elastoplasticity with a single mechanisms, and a nonassociative flow rule. The numerical simulations revealed no evidence for the incremental nonlinearities of multiple mechanisms plasticity or vertex plasticity.