The effect of the contact model on the impact-vibration response of continuous and discrete systems

Abstract

Impact is a phenomenon that is ubiquitous in mechanical design; however, the modeling of impacts in complex systems is often a simplified, imprecise process. In many high fidelity finite element simulations, an impractically large number of elements are required to model the constitutive properties of an impact event accurately. As a result, rigid body dynamics with approximate representations of the impact dynamics are commonly used. These approximations can include a constant coefficient of restitution, an artificially large penalty stiffness, or a single degree of freedom constitutive model for the impact dynamics that is specific to the type of materials involved (elastic, plastic, viscoelastic, etc.). In this paper, the effect of the contact model on the prediction of a system's dynamics is analyzed. In order to understand the effect of the impact model on the system's dynamics, simulations are conducted to investigate a single degree of freedom system, a two degrees of freedom system, and a continuous system, each with rigid stops limiting the amplitude of vibration. Five different contact models are considered: a coefficient of restitution method, a penalty stiffness method, two similar elastic–plastic constitutive models, and a dissimilar elastic–plastic constitutive model. Frequency sweeps and parametric studies show that simplified contact models can lead to incorrect assessments of the system's dynamics. In the worst case, periodic behavior can be predicted in a chaotic regime. Additionally, the choice of contact model can significantly affect the prediction of wear and damage in the system, as is evidenced by the prominence of chatter and high amplitude responses.