An elastoplastic contact force-displacement model in the normal direction:displacement-driven version

We present an elastoplastic normal force-displacement (NFD) model for spher es in collision. Among several possible applications of this model are the granular-flow simulations using a discrete-element method. The proposed NFD model is consistent with the formalism of the continuum theory of elastopl asticity, and is validated with nonlinear finite-element analyses. A key fe ature of this NFD model is the additive decomposition of the radius of the contact area into an elastic part and a plastic part. Further, the contact curvature is corrected, and the Hertzian contact mechanics generalized, to account for plastic deformation. The present displacement-driven version of the elastoplastic NFD model-whose force-driven version was presented by Vu -Quoc, Zhang & Lesburg in 1998-is developed particularly for granular flow simulations. Results of sphere-on-sphere collisions are discussed. In parti cular, the resulting coefficient of restitution varies with the incoming ve locity. A comparison of the results obtained from the present NFD models wi th those from other models is given.