CONTINUOUS CONTACT FORCE MODELS FOR IMPACT ANALYSIS IN MULTIBODY SYSTEMS

One method for predicting the impact response of a multibody system is based on the assumption that the impacting bodies undergo local defor mations and the contact forces are continuous. In a continuous analysi s, the integration of the system equations of motion is carried out du ring the period of contact; therefore, a model for evaluating the cont act forces is required. In this paper, two such contact force models a re presented, both Hertzian in nature and based upon the direct-centra l impact of two solid particles. At low impact velocities, the energy dissipation during impact can be represented by material damping. A mo del is constructed based on the general trend of the Hertz contact law in conjuction with a hysteresis damping function. The unknown paramet ers are determined in terms of a given coefficient of restitution and the impact velocity. When local plasticity effects are the dominant fa ctor accounting for the dissipation of energy at high impact velocitie s, a Hertzian contact force model with permanent indentation is constr ucted. Utilizing energy and momentum considerations, the unknown param eters in the model are again evaluated. The two particle models are ge neralized to an impact analysis between two bodies of a multibody syst em.