Coefficient of Restitution for Collinear Collisions of Elastic-Perfectly Plastic Spheres

Based on a simplified theoretical model for the normal contact interaction of two elastic-perfectly plastic spheres, an analytical solution is provided for the coefficient of restitution. The solution is expressed in terms of the ratio of impact velocity to yield velocity rather than in terms of material properties such as the yield stress which is difficult to reliably ascertain for many materials.