Influence of volumic fraction of adhesive in elastic and viscous thin bonded Aluminum/Adhesive/Aluminum plate on Lamb modes that have ZGV modes.

Before a nondestructive testing process gets set up, the sensitivity of the Lamb waves to the bonded plate's properties must be well understood. The dispersion and attenuation curves in thin bonded Aluminum/Adhesive/Aluminum plate are calculated by the Stiffness matrix method. The increase in the volumic fraction d caused the appearance of backward mode in the S0 and S2 dispersion curves. The effect of d on forward waves, and on backward waves and associated ZGV-modes, are studied. The frequencies of ZGV-modes decrease when d increases. The effects of d on dispersion and attenuation curves of the damped symmetric modes are shown. From certain values of d, and at the frequencies of the ZGV-modes, the dispersion curves of the symmetric modes are connected. This phenomenon gives rise to a C coupling mode. The attenuation levels of the ZGV-modes for different d values are calculated. The increase in d caused the shift of C-dispersion and C-attenuation curves toward the decreasing direction of the frequency axis, without significant change in the values of the phase velocity, and with slight decreases in the attenuation level of the C coupling mode.