Deformation modes of packings of frictionless polydisperse spheres

Dense granular materials are well known to demonstrate mechanical properties that are different from classical fluids or solids. An issue is the accurate prediction of mechanical properties of granular materials, which are controlled by the internal structure of the assembly of grains – where the internal structure itself depends on the history of the sample. In this work, the Discrete Element Method (DEM) approach is presented as a viable tool to investigate the behavior and dynamics of granular packings subjected to deformations. The results on uniaxial and deviatoric deformations are compared to earlier results on isotropic deformation. As main result, the evolution of pressure and coordination as a function of volume fraction are reported for both uniaxial and deviatoric deformation modes. Our findings compare astonishingly well with results for purely isotropic compression. The second stress response namely anisotropy, is present as the evolution of the deviatoric stress as a function of the deviatoric strain. Similar data can be measured from experiments with the true biaxial tester which is work-in-progress, and both deformation modes are especially simple to realize experimentally.