Ultrasonic leaky waves in the presence of a thin layer

Abstract

This paper presents theoretical and experimental results on the problem of bounded acoustic beam reflection at the Rayleigh angle from a fluid-solid interface which is loaded by a thin solid layer. The theoretical developement exploits the framework of existing theory to yield a simple, analytic model which is reasonably accurate for thin layers. It is shown that the influence of the layer is contained entirely in the dispersive Rayleigh wavespeed and the thickness-dependent displacement parameter Δs . Measurements of the reflected acoustic field amplitude have been performed on several samples of stainless steel loaded with a copper layer. We have found reasonably good agreement between the theoretical model calculations and experimental measurements for ratios of the layer thickness to the Rayleigh wavelength as large as 0.3. Beyond this value, some disparity is observed, particularly in the calculation of the thickness-dependent Rayleigh wavespeed.