Identification of Nonlinear Viscoelastic Parameters Based on an Enhanced Oberst Beam Method

This work deals with payload vibration insulation in aeronautic applications. The main objective is to design stabilization devices for optical devices. To achieve this goal, polymer materials have been used because they provide damping and flexibility in order to isolate the optical devices from vibrations and shocks. This kind of material exhibit a mechanical behavior that strongly dependent on the temperature, the strain amplitude and the frequency. The purpose of this paper is to give a new identification method of the viscoelastic parameters based on the Oberst beam test. The aim is to carry out the dependence of the elastomer mechanical properties on the strain amplitude. By coupling this test with Dynamic Mechanical Analysis, it is possible to obtain the mechanical behavior of viscoelastic material according to the strain amplitude and the frequency. To achieve this goal, the experiment derived from the Oberst beam set-up and ASTM E756-05. The time response signal is post-processed using nonlinear unconstraint optimization method in order to identify the instantaneous frequency and damping ratio of the first eigenmode. Then, it is possible to recover the storage modulus and the loss factor of the polymer according to the strain amplitude using a finite element model of the setup. Finally, the identified frequency and amplitude dependent models are taken into account to carry out numerical simulations on the whole mechanical device.