Fe-simulations of a direct and a true simple shear test within a polar hypoplasticity

Two different plane strain shear testers used to measure properties of granular materials are compared: a direct shear tester and a true simple shear tester. The evolution of deformations and stresses within cohesionless granular bodies during shearing is investigated with a finite element method on the basis of a hypoplastic constitutive model extended by polar quantities: rotations, curvatures and couple stresses. A mean grain diameter is used as a characteristic length. The constitutive model takes into account the effect of pressure, void ratio, direction of deformation rate and mean grain diameter. The attention is focused on the effect of boundary conditions on the shear zone formation.