The rapid monitoring of structures using interdigital Lamb wave transducers

Abstract

The use of interdigital PVDF transducers for the quick inspection of large, plate-like structures is discussed. The transducers are designed to excite a particular Lamb mode in the structure, the region of the structure that is insonified being controlled by the transducer design. An example is given of the monitoring of an aluminium plate by a single, circular transducer operating in pulse-echo mode, the a0 Lamb mode at a frequency of about 1 MHz being transmitted and received. The transducer is split into segments so that the angular location of a reflector can be defined, the radial location of the reflector being determined from the time of arrival of the echo.

Interdigital sensors and transducers

“…Using this configuration, an enhancement in sensor selectivity can be expected. Somewhat analogous to customizing electric field patterns to the MUT is the approach of customizing wave propagation characteristics in acoustic sensors [188]. One may expect a transition from analog circuits to a mixed-signal circuits, where such customization would be achieved with digital circuitry.…”

“…Although the applications of SAW devices in NDT have been under intensive development for a long time, many measurement-type modifications remain an open territory for future studies. Further deployment of array sensors and sensor networks is expected for measurement of multilayer properties (e.g., in composite materials [189]) and monitoring of distributed infrastructure [188]. Transition to autonomously operating power-harvesting nondestructive sensors is expected in such fields as avionics, power generation, and naval technology.…”

Structural Health Monitoring Using Guided Ultrasonic Waves

“…Lamb wave applications show studies with voltage amplitudes in the range of: 1-20V (PZT transducers - [11,79,121]), 100-150V (PZT transducers [34,122], PDVF transducers [123], angle-beam transducer [112]) and even 500V (air-coupled transducers [124]). It appears that this important information is often not given in application papers.…”

Structural health monitoring in composite materials using frequency response methods

“…This equality must be solved numerically for a given set of constant material properties. Examples of dispersion curves can be found in several places in the literature, and will not be focused on in this paper [13][14][15][16][17][18].…”

“…Since the mid-1990's, Cawley's group has been working to optimize the generation of directional Lamb waves [13,14]. To allow the implementation of Lamb waves on a real structure, they have been developing flexible, cheap Polyvinylidenedifloride (PVDF) transducers in order to both generate and detect waves.…”