Abstract

In this paper, detection of the fundamental shear horizontal (SH0) guided wave mode in a plate using a surface-bonded Fabry–Perot interferometer formed by a pair of tandem chirped fiber-Bragg-gratings (CFBG-FPI) has been investigated both theoretically and experimentally. Using the developed theory, the underlying mechanism that governs the sensor's response to SH0 mode is explored in detail. Then, the dependence on both the incident angle and frequency (or wavelength) of the SH0 wave is investigated. Owing to the pure shear strain induced by the SH0 mode, the fiber sensor shows a significantly different response in comparison to other ultrasonic waves, such as Lamb-type guided waves. Our results show that 1) the sensor is most sensitive to SH-type waves at an incident angle of around 45° and nonsensitive at the incident angles of 0° and 90° and 2) a minimum sensitivity is reached when the equivalent ultrasonic wavelength impinged on the fiber axis is equal to the effective length of the CFBG-FPI sensor; this effective length is close to the length of each CFBG.

© 2018 IEEE