Advances in multiscale modeling of granular materials

The paper reports recent advances in multiscale modeling of granular materials, particularly in the second-order computational homogenization method and corresponding global-local mixed FEM-DEM nested analysis scheme. The gradient Cosserat continuum and the classical Cosserat continuum are assumed for modelling granular media at the macro- and meso-scales, respectively. According to the generalized Hill’s lemma formulated for the adopted meso-macro continuum modeling the non-uniform macroscopic strain field with macroscopic strain gradients is downscaled to each representative volume element (RVE), while satisfaction of the generalized Hill-Mandel condition is ensured. The advantage of the gradient Cosserat continuum model in capturing the meso-structural size effect and the performance of the proposed second-order computational homogenization in the simulation of strain softening and localization phenomena are demonstrated, without need to specify macroscopic phenomenological constitutive relationship and material failure model.