The Effect of the Impact Model on Vibration Response of Discrete and Continuous Systems

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, the number of elements required to accurately model the constitutive properties of an impact event is impractical. 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 order to understand the effect of the impact model on the system’s dynamics, simulations are conducted to investigate a single degree of freedom, two degrees of freedom, and continuous system each with rigid stops limiting the amplitude of vibration. Five 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 show that simplified contact models can lead to incorrect assessments of the system’s dynamics and stability. 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.