The purpose of this study is to nondestructively evaluate adhesive quality using zero-group-velocity (ZGV) Lamb waves. A numerical simulation was conducted using the finite-difference time-domain (FDTD) method, incorporating a linear slip layer model to represent the bonding quality. The calculation model consisted of glass plate/epoxy adhesive/glass plate. In the numerical calculation, an input signal was cosine tapered sinusoidal waves corresponding to frequency and wavenumber of S1 mode of ZGV. As a result, two ZGV Lamb waves, S₁ and S₂ were excited. The frequency of the S₂ mode decreased with decreasing the interface stiffness. The peak amplitude of the S₂ mode increased with the decrease in interface stiffness, On the other hand, the frequency of the S₁ mode remained, and the S₁ mode amplitude decreased. The position of the minimum principal stress difference approached the center of each glass plate with the decrease in interface stiffness, which was consistent with luminance profiles in the thickness direction measured by a photoelasticity method.
TSURUDA et al. (Wed,) studied this question.