Transient modelling of Lamb waves emitted by integrated transducers using a hybrid finite element-normal mode expansion
Résumé
For a few years, the concept of integrated health monitoring of aeronautic structures has become an important issue. A promising solution is the emission of ultrasonic Lamb waves using thin piezoelectric transducers integrated to the structure. Indeed Lamb waves are known to be able to propagate over long distance and to interact with inner structural defects. One important aspect when applying Lamb waves to health monitoring is the control and optimization of their generation. Therefore, a hybrid finite element–normal mode expansion modeling technique adapted to piezoelectric transducers has been recently developed. This technique allows the determination of the amplitude of each Lamb mode as a function of the transducer parameters. So far, it had been successfully applied to the case of harmonic excitation only. In this paper, adaptation of this hybrid technique to transient excitation is presented, which enables to simulate actual experimental conditions. Contrary to other techniques presented in the literature, the present technique allows to take into account the actual electromechanical behavior of the integrated transducer. Predicted results have been successfully compared to experimental measurements performed on different types of materials.