Elastic wave propagation with kinematic discontinuity along a non-ideal interface between two isotropic elastic half-spaces

The problem of wave propagation along the interface between two elastic, isotropic, and homogeneous half-spaces is studied when the half-spaces are coupled through a vanishingly thin layer of Voigt material. It is assumed that the separation, 2H, between the half-spaces, and the complex rigidity-modulus, , of the layer are both vanishingly small, but the complex quantity /2H remains finite.In a series of experiments in which two blocks of elastic materials with or without lubricant/couplant at the interface are subjected to an external load normal to the interface, the variation of the speed and attenuation of interfacial waves, generated and detected by piezoelectric transducers, was measured as a function of external load. Assuming a nonlinear relation between external load and /2H, the experimental data is interpreted theoretically, and the best-fit parameters of the nonlinear relation are determined.For the 13 cases of interfaces studied, with or without lubricant/couplant, satisfactory agreement was found between experiment and theory, except in one case. Even in this case, the agreement is satisfactory in the lower range of load. It is hoped that this study will be useful in developing nondestructive methods of testing the bonding conditions at an interface between elastic materials by means of interfacial wave properties.