Abstract
The use of viscoelastic materials has been increasing in various industries such as automotive and electronic industries because of their excellent impact resistance or damping capability. Precise knowledge of their dynamic properties are needed to further widen the applicability of viscoelastic materials. In the present study, attenuation and the dispersion properties of a polymethyl methacrylate (PMMA) bar were examined using both ultrasonic wave propagation experiments in the higher frequency range of 25 - 200kHz and longitudinal wave propagation experiments in the lower frequency range of up to 15kHz. Since the geometrical dispersion due to three-dimensional deformation was caused by higher frequency components involved in the ultrasonic waves, the three-dimensional wave theory was employed to analyze experimental data of wave propagation. Consequently, it was found that the dynamic properties in the lower frequency range can be identified as a 3-element viscoelastic model based on the elementary one-dimensional wave theory, while those in the higher frequency range must be identified as a 5-element viscoelastic model based on the three-dimensional wave theory.
