A micro-transducer matrix design for the detection of flexural guided waves

In this paper, a new approach is proposed for the detection of ultrasonic guided waves using a LiNbO₃ single crystal-based micro-transducer matrix. This matrix was designed, manufactured, and then used to detect Lamb and Pochhammer-Chree guided waves in plate- and cylinder-like structures. This study highlights the identification of the first flexural mode F(1,1) in cylinders at low frequencies. A network analyser and a laser Doppler vibrometer (LDV) were used to characterise and study the behaviour of the micro-transducer matrix. An experimental device was designed and used to acquire electrical measurements of the micro-transducer vibrations. Then, an original experimental device was developed to generate a selected flexural guided mode in a solid aluminium cylinder. The emitter comprised two semicircular piezoelectric transducers excited with only one phased signal thanks to the inverse position of polarisation. Finally, the results prove that the flexural mode F(1,1) is selected and generated by the emitter, then detected and identified by the micro-transducer matrix.