A Perturbation Method to Model Interdigital Transducers for Use in Smart Structures

There is a need in many industries for a Structural Health Monitoring System based on a smart structure approach. We are mainly concerned in this paper with the study of permanently attached interdigital transducers (IDT) that have been developed at Imperial college [1,2] on the basis of conceptually similar devices used for the generation and reception of ultrasonic SAW in piezoelectric substrates in the electronics industry [3–5]. The specific application to the generation and reception of Lamb waves in non- piezoelectric substrates by means of IDT needs some further theoretical development in order to predict signal parameters such as the amplitude generated by the transducer for a given voltage input, the attenuation as the wave travels, and mode conversion at defects.