Flexible Interdigital PVDF Lamb Wave Transducers for the Development of Smart Structures

An Example of the Use of Interdigital PVDF Transducers to Generate and Receive a High Order Lamb Wave Mode in a Pipe

“…The transducers used in this work were interdigital PVDF ones of the type which are described in more detail by Monkhouse et al [2]. In essence they consist of a layer of piezoelectric polymer (PVDF) bonded to the structure under test.…”

“…2(a) and (b) show respectively the phase and group velocity dispersion curves for a 6.5mm ductile iron plate, which were plotted using Disperse [6]. The first constraint on the selection of an operating point was that even with 50Jlm thick copper plated electrodes, interdigital PVDF transducers still only have a satisfactory response above about 0.75MHz [2]. Due to the thickness of the material, the non-dispersive points on the lower modes Ao, S0 and A1, which would be the preferred operating points on a thinner plate, were at frequencies too low to be used.…”

“…The width of the fingers increases towards the centre of the transducer to simulate the effect of a Hanning window around the spatial excitement. This improves wavelength selectivity by reducing the sidebands around desired wavelengths [2]. The width of the transducer was chosen to make it approximately square.…”

“…Interdigital PVDF transducers have been used previously in signal processing applications [1] to generate acoustic waves in piezoelectric substrates. This paper in conjunction with that of Monkhouse et al [2] aims to provide an overview of the work accomplished so far at Imperial College in the use of interdigital PVDF transducers to transmit and receive Lamb waves in certain structures for non-destructive evaluation purposes. Interdigital PVDF transducers may be permanently bonded to either flat of curved surfaces and this attribute together with their low cost means that they are potentially suitable for "smart structure" applications.…”

Application of Piezoelectric Transducers in Structural Health Monitoring Techniques

“…Their damage detection capabilities has been known for a long time [1,2]. By implanting small piezoelectric transducers into the structures, Lamb waves can be emitted and received and it is theoretically possible to monitor a whole given area [3,4].…”