Inhomogeneous interface waves in a thin layer between half spaces and their relationship to lamb waves

We consider inhomogeneous guided interface waves and Lamb waves in a thin isotropic elastic layer embedded between two half spaces (I) and between two plates (II), respectively. Dispersion curves corresponding to true or propagating modes in configuration (I) are known to exist only below the shear velocity of the half space. These modes coincide with some Lamb wave dispersion curves for configuration (II) depending on the thicknesses of the plates and thin embedded elastic layer. The corresponding Lamb waves have a wave structure that is dominant in the embedded layer. It is shown that inhomogeneous (or evanescent) dispersion curves in configuration I also coincide with some Lamb modes of configuration II. These curves exist in a region above the shear velocity of the half spaces (plates). The corresponding Lamb wave structures are also shown to have predominant displacement in the adhesive region.