A Two-Step Guided Waves Based Damage Localization Technique Using Optical Fiber Sensors

Abstract

Structural health monitoring (SHM) systems help in reducing maintenance cost and avoiding catastrophic failure of the structure. As a result, they have been a focus of research for the past few decades. Ideally, the methods employed should be low cost and able to detect and localize small levels of damage reliably and accurately. This paper describes a guided waves (GW) based two-step technique for damage detection and localization using fiber Bragg grating (FBG) sensors. The FBG sensors offer benefits such as the ability to be embedded and multiplexed as well as being lightweight and insensitive to electric and magnetic fields, and they have long been seen as a promising solution for the GW measurements in structures. Unfortunately, in the conventional wavelength-based interrogation they have very low signal to noise ratio and as a result low sensitivity. Therefore, the FBG sensor is incorporated in the edge filtering configuration. The major challenges in the use of FBG sensors for GW-based detection are their directional sensitivity and passive nature. The passive nature leads to the reduction in the available actuator–sensor (AS) pairs while the directionality makes the signal processing a challenge. The proposed two-step methodology overcomes these shortcomings of FBG sensors. In the first step the amplitude weighted elliptical approach is used to identify the hotspots due to the inadequate number of AS pairs, the elliptical approach is not sufficient for damage localization. Therefore, in order to further localize the damage the edge reflection based ray-tracing approach is implemented in the second step. Through the two step method, the damage is accurately located. The paper provides the proof of concept of the proposed methodology on an aluminum plate with simulated damage. The results indicate, that indeed the two-step methodology allows accurate damage localization and overcomes the possibility of false detections.

Guided waves based damage localization based on mode filtering using fiber Bragg grating sensors

“…The triangulation technique has been used with FBG sensors for damage detection [12,40,41]. But those studies were restricted to 50 kHz frequency.…”

“…The edge filtering approach was later used for SHM by several researchers [8][9][10][11]. The directionality was incorporated in the SHM algorithm by Soman et al [12]. A thorough review about the physics of the wave coupling and their use for SHM has been conducted by Soman et al [13] and Wu et al [14].…”

Optical Fiber Sensors for Ultrasonic Structural Health Monitoring: A Review

“…The temperature compensation tends to limit the contribution of the A 0 mode and is given as the reason for the selective sensitivity. Soman et al [159] propose a two-step damage detection process. The two-step method not only overcomes the passive nature of the FBG sensors, which reduces the number of actuator-sensor pairs, but also overcomes the directional sensitivity of the FBG sensor.…”

Location Determination of Impact on the Wind Turbine Blade Surface Based on the FBG and the Time Difference

“…In addition, due to their light structure, high signal-to-noise ratio, and strong reusability, fiber Bragg grating (FBG) has successfully been applied to the strain monitoring of various structures [ 10 ]. Matveenko et al [ 11 ] proposed a method of quoting strain values between FBG sensors at different positions and carried out tensile experiments on glass fiber samples, realizing a rough judgment of the damage location.…”