Yielding and failure of an assembly of frictional elasto-plastic particles: A computational RVE study

The constitutive behaviour of a granular material with deformable particles interacting through Coulomb friction is analysed with numerical homogenisation techniques. Using periodic boundary conditions and the finite element method, the influence of friction coefficient, hardening behaviour and particle size distribution on the stress response of an assembly of frictional elasto-plastic particles to different deformation paths is investigated. Yield surfaces and the direction of inelastic flow are computed and particular attention is paid to the flow behaviour for low stress triaxialities. It is found that densely compacted assemblies exhibit associated flow to a good approximation despite the fact that frictional sliding (as opposed to plastic deformation) constitutes the relevant deformation mechanism on the microscale; a deviation from normality is observed for low density assemblies. The numerical results are discussed against the background of theoretical models.