Abstract:Theoretical and experimental researches are carried out on nondestructive evaluation of mechanical properties of layercoated cylinders, which is of great significance for the surface quality detection and evaluation. In this work, the labdeveloped acoustic microscopy and the linefocus PVDF transducers are applied in the defocusing measurement with different coating thickness. Considering the nonlinear relationship between the propagation path of the surface wave and the defocusing distance, the geometric parameters of the PVDF transducer are related to the defocusing distance and the cylindrical radius. A correlation analysis method is developed based on V(f,z) analysis to extract the dispersion curves. Combined with the characteristicsof wave propagation of coating materials, the acoustic parameters of cylindrical coating materials are inversed by fitting the theoretical curves to the experimental ones, using the particle swarm optimizationbasedsimulated annealing(PSOSA) algorithm. Hence, the elastic constants of coatings are obtained. The experimental results indicate that the measurement results well match the theoretical counterparts, which prove that this method is reliable and accurate. This method provides a powerful technique for the nondestructive evaluation of cylindrical coating materials. Furthermore, it can be a great tool for evaluation of material properties in Surface Engineering.