Elastoplastic phenomena in multibody impact dynamics

Abstract

Impact processes are often implemented in multibody system dynamics using the coefficient of restitution representing the energy loss during impact. In this paper a multiscale simulation approach is used in order to evaluate the coefficient of restitution numerically including the phenomena of wave propagation and, in particular, plastic deformation. For the numerical investigation four different models are presented in the following: a completely nonlinear finite element (FE) model, a modal model of the elastic parts of the body combined with a nonlinear FE model of its contact region, a modal model with quasi-static FE contact, and a modal model with an elastostatic Hertzian contact law. The modal models with FE contact are very efficient for investigating repeated impacts of the bodies including the deformation history of the contact region. Simulations and experiments of repeated frictionless impacts on aluminum bodies show, due to plastic deformation of the contact area, an increase of the coefficient of restitution with increasing numbers of impacts. Finally, plastic deformation does no longer spread out and a stationary value is reached. In the stationary phase impacts on a compact body shows no energy loss, while for impacts on a slender body the remaining energy loss during impact is purely due to wave propagation phenomena. Simulations show a strong dependency of the coefficient of restitution on the yield stress of the used material, that is also verified by experiments.