GUIDED ELASTIC-WAVES IN ORTHOTROPIC SURFACE-LAYERS

Propagation of guided waves along the interface of an elastic surface layer of uniform thickness overlying an elastic homogeneous half-space is examined. The structure is made of materials with arbitrary strain energy functions. To gain understanding of the propagation characteri stics and their dependence on the elastic constants and mass densities , the mathematically tractable case of material orthotropy is consider ed. For propagation along a material axis of symmetry, the dispersion equation is obtained in explicit form when the axes of symmetry of the two materials coincide and one of them is normal to the plane separat ing the surface layer from the underlying half-space. Analysis of the dispersion equation reveals the propagation characteristics of interfa cial waves and their dependence on the material parameters. Propagatio n occurs either in single or multiple modes, depending on the material parameters of both the surface layer and the underlying half-space. T he low-frequency phase speed is obtained from the dispersion equation in terms of wavelength and layer thickness, elastic constants and mass densities. The influence of the two materials on phase speed as it de viates from its value in an orthotropic half-space is, thus, given exp licitly. Parameter conditions are defined under which guided waves are not allowed to propagate in certain frequency regimes. Numerical resu lts complement the analysis. (C) 1998 Elsevier Science B.V.