A nonlocal contact model for adhesive elastic-plastic particles

We present a contact model able to capture the response of interacting adhesive elastic-plastic particles. The model is built upon the Method of Dimensionality Reduction which allows the problem of a 3D axisymmetric contact to be mapped to a semi-equivalent 1D problem of a rigid indenter penetrating a bed of independent Hookean springs. Plasticity is accounted for by continuously varying the 1D indenter profile subject to a constraint on the contact stress. By considering the incompressible nature of this plastic deformation, the contact model is also able to account for the nonlocal effects of neighboring contacts, including formation of new contacts from outward displacement of the free surface. JKR type adhesion is recovered easily by simply allowing the springs to ‘stick’ to the 1D indenters surface. Additionally, we account for the rapid stiffening in the force-displacement curve under high confinement (e.g. during powder compaction) by allowing a superimposed bulk elastic response to be switched on. To validate the model, we compare it to finite element simulations of adhesive elastic-plastic contact. These comparisons show that the proposed contact model is able to accurately capture plastic displacement at the contact, contact stress, particle volume, contact radius, and force as a function of displacement under a variety of complex loadings.