Importance of event detection and nonlinear characterization of dynamical systems with discontinuity boundary

In this study, the response of a dynamical system with an increasingly stiff freeplay nonlinearity is investigated. Numerical simulations are carried out on a forced Duffing oscillator with low, intermediate, and hard levels of contact. This study is intended to explore the effects of contact stiffness on the system response as the contact approaches hard impact. The importance of accurately capturing points of contact in the system will also be examined. Preliminary results indicate significant shifts in the frequency-response curves of the system along with reduction in amplitudes. These effects are amplified if the contact is asymmetrically spaced in the system. Further, for soft contact, event detection is not always essential to result accuracy. However, for hard contact, event detection is important to ensure accurate results. Differences with/without event detection range from “poorly converged” appearance to slower transient decay to incorrectly predicting potentially dangerous subharmonic resonances.