Measurements of dispersion curves of leaky Lamb waves using a lens-less line-focus transducer

This paper presents a new method of measuring dispersion curves of leaky Lamb waves propagating in a thin plate. The measurement system is based on a lens-less line-focus transducer and its defocusing measurement technique. A new waveform processing method known as V(f,z) method is introduced for analyzing the measured waveforms and for extracting the dispersion relation. For two thin-plate samples, namely a 150 μm thick alumina plate and a 320 μm thick stainless steel plate, the dispersion curves of several lower order modes of leaky Lamb waves have been experimentally determined in the frequency range of few to 25 MHz. The experimental dispersion curves have then been compared with the theoretical ones. Excellent agreement is observed. It is then verify that this method indeed provides a convenient and accurate way for experimentally measuring dispersion curves of leaky Lamb waves of thin-plate samples.