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Open AccessArticle

High-Density Distributed Crack Tip Sensing System Using Dense Ultra-Short FBG Sensors

1
School of Information Engineering, Wuhan University of Technology, Wuhan 430070, China
2
National Engineering Laboratory for Fiber Optic Sensing Technology, Wuhan University of Technology, Wuhan 430070, China
*
Author to whom correspondence should be addressed.
Sensors 2019, 19(7), 1702; https://doi.org/10.3390/s19071702
Received: 17 March 2019 / Revised: 4 April 2019 / Accepted: 8 April 2019 / Published: 10 April 2019
(This article belongs to the Special Issue Distributed Optical Fiber Sensing)
Crack generation starts at the crack tip, which bears the highest stress concentration. Under further stress, the crack propagates and leads to severe structural damage. To avoid such damage, the identification of the crack tips, and monitoring of the surrounding stress and strain fields, are very important. In this work, the location of, and strain distribution monitoring around, the crack tip are achieved using a dense ultra-short (DUS) fiber Bragg grating (FBG) array together with an improved optical frequency domain reflectometry (OFDR) interrogator. The adjacent grating interference correlation algorithm helps overcome the limitation on the demodulation precision, which is imposed by the inherently broad reflection spectra of individual ultra-short gratings. High spatial resolution measurement of the strain profile around the crack tip is performed at different levels of induced strain. Furthermore, the vertical-crossed layout is adopted to avoid the omission of cracks, which usually occurs in the case of the one direction layout. We achieve 1 mm spatial resolution and 7.5 m detection distance. Location of a single crack, multiple cracks, and an oblique crack was realized experimentally by locating the crack tips. The experimental results are consistent with the theoretical analysis, verifying the feasibility of the DUS-FBG system for high-density distributed crack tip sensing. View Full-Text
Keywords: optical fiber sensing; crack tip; dense ultra-short fiber Bragg grating; high density; distributed sensing optical fiber sensing; crack tip; dense ultra-short fiber Bragg grating; high density; distributed sensing
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MDPI and ACS Style

Gui, X.; Li, Z.; Fu, X.; Wang, C.; Wang, Y.; Li, H.; Wang, H. High-Density Distributed Crack Tip Sensing System Using Dense Ultra-Short FBG Sensors. Sensors 2019, 19, 1702.

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