Detection of Crack Locations in Aluminum Alloy Structures Using FBG Sensors

Abstract

This study investigated the reflected spectral deformation mechanism of fiber Bragg grating (FBG) sensors with crack propagation. This analysis was performed based on the simulated FBG response by applying modified-transfer matrix modeling (TMM) with the strain states, which were extracted by the finite element method (FEM) analysis. Experimental data were obtained from FBG sensors bonded in an aluminum alloy structure and subjected to multiple crack lengths, and the strain values were obtained by digital image correlation (DIC) technology. Based on the simulations and the experimental full spectral response, we compared the performance of two damage features: The full width at half maximum (FWHM) and the spectral difference. In addition, results showed that the two features were insensitive to experimental noise and were highly sensitive to the complex strain field caused by crack propagation. Moreover, the damage features changes in the crack propagation process also provided a way for crack position measurement. Ultimately, the 10 mm grating lengths sensors showed better performance to the crack detection with longer sensitivity distance. According to the research in this paper, the crack position was quantitatively determined by evaluating different damage features of the reflected spectrum.

Design Reliable Bus Structure Distributed Fiber Bragg Grating Sensor Network Using Gated Recurrent Unit Network

“…Figure 14 shows the detection results obtained by the GRU model when the number of FBG sensors is seven. As shown in the figure, the proposed model capable of detecting the Bragg wavelength of each FBG, even when the spectra of FBGs are partially overlapped (see strain steps 7,11,13,16,18,21,24,29,31,36,38,43,45,49,51, 56 and 58) and fully overlapped (see strain step 8, 12, 17, 23, 30, 37, 44, 50 and 57). Moreover, the average RMS errors of our proposed GRU model for the four different cases, such as 3-FBG, 5-FBG, 7-FBG, and 10-FBG, are summarized in Table 4.…”

“…The sensor network, comprising several sensors, is used as a crucial component of the IoT framework to attain multi-point measurements for a given physical environment [ 1 , 2 , 3 ]. From a various number of sensor network categories, Fiber Bragg Grating (FBG) sensors are widely used in complex environments because of their strong anti-electromagnetic interference, slight size, corrosion resistance, high-temperature tolerance, high sensitivity, and strong multiplexing capabilities [ 3 , 4 , 5 , 6 , 7 , 8 ]. Additionally, they displays massive bandwidths, have few broadcast victims, allow vast topographical coverage, and can be operated without electrical powering of local batteries to decrease the risk of sparking in flammable surroundings [ 1 , 3 , 4 ].…”

Characterization of OFDR distributed optical fiber for crack monitoring considering fiber-coating interfacial slip

“…Over the past two decades, many optical fiber sensors have been proposed to monitor cracking in both metal and concrete structures due to their advantages over traditional methods such as small size, light weight, anti-corrosion resistance, immunity to electromagnetic interference, high sensitivity, and capability of being multiplexed in a sensor network. 12 For example, Zhang et al 13 used fiber Bragg grating (FBG) sensors to detect crack location in aluminum alloy, and Mao et al 14 employed FBG sensors to monitor steel-corrosion induced concrete surface cracking. However, these FBG sensors only detect cracking at a fixed location and unable to monitor multiple cracks appeared in a large area.…”

Intensity and Wavelength-Division Multiplexing Fiber Sensor Interrogation Using a Combination of Autoencoder Pre-Trained Convolution Neural Network and Differential Evolution Algorithm

“…Fiber Bragg grating (FBG) sensor is a type of fiber sensor that commonly used to measure temperature, strain, vibration, pressure, and several other physical quantities [7][8][9][10]. The strain-sensing concept of FBG sensor can be determined by the shift of the peak wavelength of FBG due to the variation of physical parameters [11][12]. In FBG sensor system, a self-healing structure is a good solution to increase the reliability and survivability issue of the sensor network [13].…”