A dual-mode piezoelectric transducer for selective excitation and reception of bidirectional S₀ and SH₀ waves

Transducers play a crucial role in guided wave-based structural health monitoring (SHM). Most transducers are designed to excite a single wave mode to reduce signal complexity from multimodal characteristics. However, different wave modes detect different defects, necessitating multiple transducer types for comprehensive defect identification. This conflicts with the goal of minimizing sensor numbers for large-area monitoring. In this work, a dual-mode piezoelectric transducer (DMPT) is introduced for the selective excitation and reception of bidirectional S0 (fundamental symmetric Lamb wave) and SH0 (fundamental shear horizontal wave) waves. The DMPT consists of two identical piezoelectric ceramic wafers placed side by side with two pairs of electrodes. By selecting different electrode pairs as active, the operational mode can be easily changed. Finite element simulations and experimental tests show that in S0 mode, the DMPT generates bidirectional S0 waves within 300~400 kHz along the working direction. In SH0 mode, it produces bidirectional SH0 waves across 125~175 kHz in the same direction. Additionally, the DMPT selectively detects and identifies S0 and SH0 waves in the working direction while attenuating them in the non-working direction. The proposed DMPT offers a cost-effective solution for selective excitation and reception of bidirectional S0 and SH0 waves using a single transducer, potentially reducing the number of transducers needed in sensor networks, which is significant for SHM applications.