Estimation of dynamic paramaters for viscoelastic materials by longitudinal vibration testing using pulse method

In this paper, two methods based on longitudinal vibration testing of a thin bar are proposed for measuring the dynamic parameters of the viscoelastic materials in a wide frequency region. First, an inverse method by FEM based on resonance measurement is presented, in which the measured response of longitudinal vibration is asymptotically approached by the forward calculated response from the finite element computation, then the dynamic parameters can be obtained. Second, an improved wave propagation measurements based on free end longitudinal vibration signal is described. In which the dynamic parameters in the frequency range of 1kHz to 5kHz are calculated from the vibration velocity ratio between the long bar and the short bar.