Lamb wave propagation in elastic plates coated with viscoelastic materials

Abstract

This paper addresses the effects of attenuative coatings on the dispersion characteristics of Lamb wave propagation in elastic plates. The topology of phase velocity and guided wave attenuation spectra is analyzed as a function of the coating internal damping (longitudinal and shear bulk attenuations) and it is proved that in contrast to elastic plates, all modes are propagating albeit with large attenuation in some cases. An energy-based correspondence between the dispersion of the attenuative bilayer and that of a related elastic bilayer is derived in order to investigate separately the effects of the longitudinal and shear bulk attenuations on the attenuation of the guided modes. It is shown that at low frequency the guided wave attenuation is only slightly affected by the longitudinal bulk attenuation, while the contribution of the shear bulk attenuation is substantial. The attenuation characteristics of shear horizontal modes are compared with those of Lamb modes in order to identify the mode and the frequencies which result in minimum guided wave attenuation.