Guided ultrasonic propagation in the tri-layer structures. Application to the reconstruction of their material properties from dispersion curves

Abstract

This paper deals with the guided ultrasonic propagation in the tri-layer structures. The propagation model and the procedure used to determine the dispersion curves and the displacement field in the structure are those presented earlier in B. Bougaze et al. [Eur. Phys. J. Appl. Phys. 32 , 207 (2005)] and tested for the case of (aluminium/adhesive/aluminium) structure. Here, we consider the case of a tri-layer structure presenting two different adherents: copper and steel. We adjusted our programs for this case and determined the dispersion curves and the displacement field in the structure. The obtained dispersion curves are then used to reconstruct the material properties of the tri-layer structure via a proposed numerical inverse method based on an optimization process. These material properties include the longitudinal and shear wave velocities as well as the density of each layer of the structure. The agreement between the reconstructed and the exact material properties is very well demonstrating the efficiency of the proposed numerical inverse method.