Inverse determination of thickness and elastic properties of thin layers and graded materials using generalized Love waves

Determination of the mechanical and geometrical parameters of thin coatings and surface layers in materials is of great practical importance in engineering and technology. In this work the authors present a novel inversion procedure for simultaneous determination of thickness, shear elastic constant and density of thin coating layers in materials. The inversion procedure is based on measurements of the dispersion curve for Love surface acoustic waves. The inverse problem is formulated as an optimization problem with the appropriately designed objective function, depending on the material parameters of the coating layer, ultrasonic frequency, and the experimental data, i.e., measured phase velocity of the surface Love wave. The minimization of the objective function provides three parameters of a thin layer, i.e., its thickness, shear elastic constant and density. The agreement between the results of calculations with the proposed inversion method and the experimental data was good.