Influences of Elastic and Viscous Moduli on Laser-Generated Lamb Waves in Viscoelastic Plates

Abstract

The study of the propagation of laser-generated Lamb waves in viscoelastic plates, after taking into account the viscoelastic and thermophysical properties, is reported. Based on the thermoviscoelastic theory, a finite-element model for the laser-generated Lamb waves is developed in the frequency domain, and the temporal temperature and displacement waveforms are obtained by using inverse fast Fourier transforms. The influences of each elastic and viscous modulus $(C_{11}^{\prime },\; C_{22}^{\prime },\; C_{12}^{\prime },\; C_{66}^{\prime },\; C_{11}^{{\prime }{\prime }},\; C_{22}^{{\prime }{\prime }},\; C_{12}^{{\prime }{\prime }},$ and $C_{66}^{{\prime }{\prime }})$ on the propagation of the laser-generated Lamb waves (mainly for the $S_{0}$ and $A_{0}$ modes) are investigated in detail. The numerical results show that the attenuation of the $S_{0}$ mode is mainly determined by $C_{22}^{\prime },\; C_{12}^{\prime },\; C_{11}^{{\prime }{\prime }}$, and $C_{12}^{{\prime }{\prime }}$, and is independent of $C_{66}^{\prime }$ and $C_{66}^{{\prime }{\prime }}$. In addition, the attenuation of the $A_{0}$ mode is more influenced by $C_{11}^{\prime },\; C_{22}^{\prime },\; C_{11}^{{\prime }{\prime }},$ and $C_{12}^{{\prime }{\prime }}$. The finite-element method in the frequency domain provides a useful tool to investigate the mechanical properties of the viscoelastic plates.