Scattering of plate waves by a cylindrical inhomogeneity

To develop a quantitative in situ structural health-monitoring system, which measures the scattered wave field using piezoelectric sensors, that can determine the size and severity of structural anomaly in plate-like structures, it is important to characterize the interaction of plate waves with damages. This paper presents a theoretical and experimental investigation of the scattering behavior of extensional and flexural plate waves by a cylindrical inhomogeneity. Exact solutions are obtained by using the wave function expansion method, while the Born first approximation has been employed to derive explicit solutions that form the basis for efficient parametric inversion and eigenfunction back-propagation. To verify the analytical methods, experiments have been performed on a metallic plate, with a cylindrical mass being bonded to one side of the plate to simulate damage. Circular piezoelectric transducers were surface mounted on the plate to generate and measure stress waves. A good correlation has been observed between the analytical solutions and the experimental data. The present results reveal that the scattering pattern is strongly dependent on the ratio of wavelength to the size of the inhomogeneity, indicating the importance of selecting the appropriate diagnostic frequency as well as the optimal placement of sensors to achieve maximum sensor response.