NUMERICAL SIMULATIONS OF THE INCREMENTAL RESPONSES OF IDEALIZED GRANULAR-MATERIALS

Herein we investigate the incremental structure of several constitutiv e 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 ampli tude but different directions. Idealized granular materials are found to exhibit an incrementally piecewise-linear behavior that is describe d by elastoplasticity with a single mechanism, and a nonassociative fl ow rule. The numerical simulations revealed no evidence for the increm ental nonlinearities of multiple mechanism plasticity or vertex plasti city.