Use of the two channels method to determine the guided waves damping coefficients of an asymmetrically fluid-loaded plate: Theory and experiment

Abstract

Exact and approximate formalisms describing the interactions of acoustic plane waves with an elastic isotropic plate immersed between two different fluids are presented. This is an extention of the Fiorito, Madigosky, and Berall (FMU) theory. Resonant approximations are given for the reflection and transmission coefficients, which assume light fluids loading. These approximations show that the resonance widths are the sum of two independent partial widths, each of them being related to one fluid and to the plate physical properties. In addition, experimental results are presented for a steel plate; the damping coefficients of the propagating leaky Lamb waves along the loaded plate are measured in two different loading situations. In the first situation the plate is embedded in water (water loading on both sides), while in the second situation it is loaded with water on one side and acetone on the other side. The experimental damping coefficient of the acetone-steel-acetone structure is deduced therefrom. The damping coefficient obtained in each case is then compared to the theoretical half resonance width, and the experimental results are found to be in good agreement with the theoretical predictions.