Measuring Lamb wave dispersion curves of a bi-layered plate and its application on material characterization of coating.

This paper investigates the Lamb wave dispersion curves of a bi-layered plate and evaluates the feasibility of using the dispersion data to characterize the coating's material properties. The measurement of dispersion curves is based on a focusing PVDF transducer operating in a pulse/echo mode. An image displaying technique is used to determine the dispersion relation of Lamb waves from the measured data. Multiple dispersion curves of Lamb waves are accurately determined over a wide frequency range (4 to 20 MHz). Lamb wave dispersion curves for thin metal sheets electro-deposited with nickel coatings are measured. The elastic constants of the nickel coating are determined by comparing the experimental dispersion data with the theoretical ones calculated numerically. Potential applications of this measurement method are addressed.