Dynamic parameters estimation based on longitudinal vibration using an inverse method in FEM

Viscoelastic materials have been widely used in the noise and vibration control since they can provide high damping capability over wide temperature and frequency ranges. Designing or selection of damping structure requires the knowledge of dynamic performance of viscoelastic materials. Resonant bar technique is a classical method which has been used for the parameters measurement of the viscoelastic materials. In this paper, an inverse method for dynamic parameters estimation of viscoelastic thin bar is presented, in which the measured response of the bar longitudinal vibration is gradually approximated by the forward calculated response from finite element computation. Firstly, the loss factor is estimated from the displacement magnitude ratio between the driven end and the free end of the bar. Then the complex-modulus is estimated from the resonant frequency. The accuracy of experimental results validates the proposed inverse method.