Surface waves in materials with functionally gradient coatings

Abstract

Surface wave excitation and propagation in a half-space with a continuous dependence of elastic properties on depth has been considered. The total wave field generated by a given surface load can be represented as a convolution of the Green’s matrix of the medium with the vector of surface stresses, while the traveling surface waves are described by the residues from the poles of the Green’s matrix Fourier symbol. Comparison of the gradient and multilayer models shows that with a high enough number of partitions (layers), the dispersion properties and amplitude-frequency characteristics of surface waves in FGMs are described by the curves obtained upon a steplike approximation of gradient properties; however, with high contrast properties, the multilayer model can be more time-consuming. The effect of the vertical inhomogeneity of the medium on the surface wave characteristics has been analyzed for a series of typical dependences occurring in micro- and nanocoatings due to diffusions or technological features of sputtering and gluing of protective films.