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.
Complex-modulus measurement by longitudinal vibration testing
A simple method is presented to measure the complex modulus of suitably rigid, linear viscoelastic materials over the audio-frequency spectrum. The case is considered where one end of a rod of the material is driven harmonically and the complex displacement ratio is measured. The effect of a rigid end mass on the free end is accounted for. It is shown that, at specific frequencies near resonance, it is easy to obtain modulus data with standard equipment usually found in the vibration laboratory.
Speed of Sound in Castor Oil
The speed of sound in Baker DB‐grade castor oil has been measured at temperatures between 0° and 40°C and pressures between atmospheric and 110 MPa (megapascals). The data have been fitted with an empirically determined equation.