Measuring dispersion curves of acoustic waves using PVDF line-focus transducers

This paper presents a new method for measuring dispersion curves of elastic waves propagating in thin plates and layered media. The measurement is based on line-focus PVDF transducers that have been used successfully to measure surface acoustic wave velocities for both isotropic and anisotropic bulk materials. In this study, the transducer has been further applied to thin plates and layered media for measuring their wave velocity dispersion. In order to obtain the dispersion relation, a new waveform processing method is introduced. A theoretical analysis is given to explain how this method can be used for the determination of velocity dispersion curves. Experimental testing on two samples, a thin glass plate and a glass/silicon layered medium, were carried out using the line-focus PVDF transducer and the new waveform processing technique. The experimental results when compared to theoretical values indicate that the wave dispersion curves can be determined accurately. Discussions on the measurement system and its future application will be detailed.