Non linear dynamics of a structure supported by rubber mounts
Résumé
The hysteretic behavior of mechanical components permits efficient passive control of mechanical system vibrations but makes response prediction delicate due to their high non linearity. In this work, the generalized Dahl model is applied to rubber mounts used to support automotive engine cooling module. The general idea is to define an analytical model for the rubber mount, and to implement it into a global finite element model of the engine cooling module. The work presented illustrates the method on a simplified system. The rubber mounts exhibit a non-linear behavior which depends on preload and frequency. Analytical restoring force models are well adapted to simulate their behavior. An experimental investigation was conducted in order to identify the model parameters. The model considers: two envelop curves (upper and lower) which can be modeled by polynomial functions, a parameter beta that governs the transition between the compression and extension phases of the rubber mount. Based on the load-deflection hysteretic loops measured, an automated procedure was realized to extract the polynomial coefficients of the envelop curves and beta. The calculated coefficients are function of the preload and the excitation frequency. Hence, the behavior of the rubber mounts can predicted versus time. In a second time, the model identified is implemented in a finite element model of a cantilever beam supported by a rubber mount at its free end. The dynamic transient response to a forced excitation is predicted and compared to experimental results.