Identification of the Nonlinear Restoring Force Characteristic of a Rubber Mounting

This paper is concerned with the identification of the nonlinear restoring force characteristic of a rubber mounting that is part of an oscillator which is subjected to harmonic force excitation. A linearity test is successfully applied to the experimental data to detect the nonlinear behaviour of the system. It is shown that the results of linear system identification depend on the level of excitation force applied. Furthermore, the frequency response functions of the identified linear models only poorly match the measured ones. In consequence, a parametric nonlinear spring characteristic is introduced into the linear model. It is demonstrated that only one set of parameters is required to explain the system behaviour at different levels of excitation force. Also, each of the measured frequency response functions is matched more closely by the calculated frequency response of the nonlinear model.