Leaky Lamb waves of a piezoelectric plate immersed in a conducting fluid - Analysis and measurement

This paper investigates the characteristics of leaky Lamb waves propagating in a piezoelectric plate immersed in a conductive fluid. A new experimental measurement system is proposed to accurately determine the velocity variation and the attenuation of the leaky Lamb waves of a piezoelectric plate induced by fluid-lading effect. The measurement method utilizes a comb PZT transducer for generating Lamb waves and a PVDF film receiver for measuring the wave signals. A step measuring method and its signal waveform processing technique are developed, which are particularly suitable for measuring the difference in wave velocity and attenuation between a regular Lamb wave and a leaky one. The theoretical wave velocity and attenuation of leaky Lamb waves is numerically calculated based on partial wave theory. Comparison between the calculated results and the experiment data indicates that the partial wave theory may underestimates the liquid loading effects. Furthermore, it is also observed that the conductivity of the loading fluid has a much stronger influence on the characteristics of leaky Lamb wave of piezoelectric materials than what is predicted by partial wave theory. These new experimental findings indicate that the partial wave theory is inadequate for analyzing leaky Lamb wave. A modified theoretical model is needed.