Propagation of stress waves in viscoelastic media

Abstract A new method for the determination of the characteristic parameters of the stress wave propagation, such as attenuation coefficient, wave velocity, Young's modulus and the viscosity coefficient, at various frequencies in viscoelastic rods is presented. The method is based on the propagation of an arbitrary pulse in such a rod and the determination of the characteristic wave propagation parameters of each term of the Fourier series expansion of the propagating pulse. Since each term corresponds to a definite frequency, the characteristic properties of the wave propagation over a wide frequency range can be determined, by means of one test only. The analysis is based on the assumption that the viscoelastic material obeys a Kelvin-Voigt model. The stress pulse was created by means of a steel ball, projected by an air-gun, and was recorded by a transient recorder with digital memory. Two typical viscoelastic materials were tested, namely a poly(methyl methacrylate) (plexiglas) and a polycarbonate of bisphenol A (lexan). The characteristic wave propagation parameters were determined in a frequency range between 3 and 35 kHz and the results obtained agreed satisfactorily with corresponding results of previous investigators.