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 pla te and evaluates the feasibility of using the dispersion data to characteri ze the coating's material properties. The measurement of dispersion curves is based on a focusing PVDF transducer operating in a pulse/echo mode. An i mage displaying technique is used to determine the dispersion relation of L amb waves from the measured data. Multiple dispersion curves of Lamb waves are accurately determined over a wide frequency range (4 to 20 MHz), Lamb w ave dispersion curves for thin metal sheets electro-deposited with nickel c oatings are measured. The elastic constants of the nickel coating are deter mined by comparing the experimental dispersion data with the theoretical on es calculated numerically. Potential applications of this measurement metho d are addressed.