Guided waves based approach for the reconstruction of the elastic moduli of plates

In this study an inverse procedure based on the propagation of guided ultrasonic waves is proposed for the material characterization of plates. The procedure consists of an optimization problem in which the discrepancy between the dispersion curves obtained through a semi analytical finite element (SAFE) formulation and experimental dispersion curves is minimized. For both SAFE and experimental data, the joint time-frequency analysis of the continuous wavelet transform was used. The optimization scheme proposed in this study is based on an improved version of the simplex search method. The scheme inputs an initial guess of the material parameters in the SAFE formulation. The values of these parameters are iteratively updated until the discrepancy between the SAFE-based and the experimental group velocity dispersion curves is minimized. The procedure is tested to characterize the elastic properties of a 2.54 mm thick aluminum plate. As the SAFE formulation is valid for waveguides of arbitrary cross-section the method is applicable to waveguides of complex geometries and various boundary conditions.