Elastic wave mode identification and separation based on piezoelectric and fibre Bragg grating sensors

Abstract This paper analyses the sensitivity of piezoelectric (PZT) and fibre Bragg grating (FBG) sensors to propagating elastic wave modes. Elastic waves were excited by PZT actuator and sensed by PZT and FBG sensors. Elastic wave measurements with FBG sensors utilize the edge filtration method. This research conducted a detailed study of the propagation of elastic waves with the modes identification and separation in an aluminium panel. Both numerical simulations as well as experiments were utilized to study the wave propagation and investigate the differences in the sensitivity as well as the opportunity offered by both sensors for mode identification and separation. The numerical simulations were performed using the spectral element method in the time domain to capture the spatial and temporal scales involved in the simulation of elastic wave propagation and sensing, especially using FBG sensors. Results showed that the investigated PZT sensor was sensitive to S 0 and A 0 modes, while the FBG sensor was sensitive to S 0 , A 0, and SH 0 . The FBG senses the SH 0 mode effectively when its propagation is perpendicular to the sensor line. On the other hand, the FBG senses the S 0 mode effectively when its propagation is parallel to the sensor line. This sensitivity feature makes the FBG sensor interesting from the point of view of elastic wave sensing. A novel mode separation method based on the mode indicator was proposed and validated for aluminium samples. The proposed indicator was validated for a GFRP panel with unknown material properties and dispersion characteristics. It was shown that the proposed methodology could be utilized to distinguish between the symmetric and antisymmetric modes.