Triangular shaped interdigital ultrasonic guided wave transducers with improved large beam divergence and bandwidth

Interdigital transducers with rectangular shaped electrodes (RIDTs) are commonly used for their high selectivity of Lamb wave modes propagating on a targeted metal plate. Nevertheless, their use in SHM systems is limited by narrow beam divergence that implies a large number of transducers and cables to investigate large areas. This work introduces a new IDT with triangular shaped electrodes (TIDT) aimed at reaching a wider beam divergence. The objective is to compare RIDT and TIDT in terms of beam divergence, efficiency and versatility for the selection of different Lamb wave modes. This work shows the main design rules for TIDT and provides a comparison of the directivity and sensitivity with RIDT designed to generate Lamb wave modes A0@320 kHz, S0@550 kHz and A1@750 kHz- Simulations by COMSOL Multiphysics in the time domain is carried out to investigate the applications in structural health monitoring (SHM) for an array of RIDTs operating in the pitch-catch mode.