Wave Propagation across an Interface between Solid and Fluid Bounded Media

Abstract

Stress-wave propagation conditions across a plane interface between a cylindrical solid rod and confined fluid column are determined. This is done by expressing the displacement and stress fields as infinite sums over the eigenvalues found from dispersion relations resulting from the appropriate wave equations and transverse boundary conditions. To obtain numerical results, these sums are truncated and the interface boundary conditions are imposed at enough points along a radius to solve for amplitude coefficients in the truncated series. The number of terms can be increased to satisfy the boundary conditions everywhere to an arbitrary degree of accuracy. For the case of nylon to water, fields are calculated in both media from which intensity, power flow, and transmission loss are determined. New information is obtained about the stress and displacement fields as a function of frequency, axial and radial position. An end resonance similar to that of a free bar is found at which practically no energy couples to the water. [Research supported in part by the Office of Naval Research, The Link Foundation, and Department of Defense's Joint Services Electronics Program.]