SH SURFACE-WAVES IN A HOMOGENEOUS GRADIENT-ELASTIC HALF-SPACE WITH SURFACE-ENERGY

The existence of SH surface waves in a half-space of homogeneous mater ial (i.e. anti-plane shear wave motions which decay exponentially with the distance from the free surface) is shown to be possible within th e framework of the generalized linear continuum theory of gradient ela sticity with surface energy. As is well-known such waves cannot be pre dicted by the classical theory of linear elasticity for a homogeneous half-space, although there is experimental evidence supporting their e xistence. Indeed, this is a drawback of the classical theory which is only circumvented by modelling the half-space as a layered structure ( Love waves) or as having non-homogeneous material properties. On the c ontrary, the present study reveals that SK surface waves may exist in a homogeneous halfspace if the problem is analyzed by a continuum theo ry with appropriate microstructure. This theory, which was recently in troduced by Vardoulakis and co-workers, assumes a strain-energy densit y expression containing, besides the classical terms, volume strain-gr adient and surface-energy gradient terms.