Shear acoustic waves polarized along the ridged surface of an isotropic solid plate: Mode coupling effects due to the shape profile

Abstract

The aim of the paper is to describe the modes coupling due to scattering on small one-dimensional irregularities (parallel ridges) of the surface of isotropic solid plates, when shear horizontal waves (SH-waves) polarized along the ridges propagate perpendicularly to them. In a previous paper [Valier-Brasier et al., Appl. Phys. Lett. 93, 164101 (2008)], an analytical model was presented for describing the roughness by inertia of “teeth” which bound the ridges, through an impedancelike boundary condition, whatever shape of the roughness is. In the present paper, this shape is accounted for through a more sophisticated model, used previously for describing the effects of the roughness of walls on acoustic pressure fields in fluid-filled waveguides [Valier-Brasier et al., J. Appl. Phys. 106, 034913 (2009)], and adapted here in order to describe the modes coupling due to the scattering of these SH-waves. Moreover, the effect of a spatial periodicity of the ridges on the modes coupling is discussed, emphasizing the role played by the phase-matching (phonon relationship). Finally, comparison between both models (“teeth inertial” and “shape profile” models) is given and discussed.