Towards a mechanistic model for the interaction between plastically deforming particles under confined conditions : A numerical and analytical analysis

Triaxial compression of plastically deforming particles was studied with the finite element method in order to identify the mechanisms that underlie the particle response under confined conditions. In addition to the established elastoplastic behaviour at small and intermediate strains, the coalescence of plastic zones centred at contacts resulted in a reduced stiffness, whereas a significantly increased stiffness was seen once the material displaced by plastic deformation filled the ambient void space, signifying the onset of a stage dominated by elastic volume reduction. Moreover, an analytical model for multiple simultaneous contacts was formulated, assuming that the deformed particle shape could be approximated by a truncated sphere and that the behaviour of each individual contact could be described in terms of a hardness. The thus obtained model exhibited a promising agreement with the numerical results.