Stoneley Waves in Media with Microstructure

The role of microstructure in affecting propagation of antiplane Stoneley waves, that are waves localized at the discontinuity surface between two perfectly-bonded half-spaces, is considered. Microstructure is described within the linear theory of isotropic couple stress elastic materials with micro-inertia. The dispersion relation is a symmetric tri-term combination of the Rayleigh functions in the relevant half-space with a coupling term. In contrast to classical elasticity, where antiplane Stoneley waves are never supported and in-plane waves exist only inasmuch as shear velocities for the half-spaces are close enough, it is found that propagation is largely possible, although it occurs beyond a cuton frequency. For the latter, an explicit expression is given alongside dispersion curves. These results may adopted in next-generation non-destructive testing (NDT) appliances to account for the material microstructure.