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Journal of Sensors
Volume 2017 (2017), Article ID 2857693, 7 pages
https://doi.org/10.1155/2017/2857693
Research Article

Mechanism of Subordinate Peak Skewing of FBG Sensor during Cracks Propagation Monitoring on Aluminum Alloy Structure

1School of Energy and Power Engineering, Beihang University, 37 Xueyuan Rd., Haidian District, Beijing 100191, China
2Collaborative Innovation Center for Advanced Aero-Engine, Beihang University, 37 Xueyuan Rd., Haidian District, Beijing 100191, China
3School of Reliability and Systems Engineering, Beihang University, 37 Xueyuan Rd., Haidian District, Beijing 100191, China

Correspondence should be addressed to Wei Dai

Received 7 August 2017; Revised 30 September 2017; Accepted 9 October 2017; Published 20 November 2017

Academic Editor: Lei Yuan

Copyright © 2017 Bo Jin et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This study investigates the variety of the spectra features of fiber Bragg grating (FBG) around the crack tip during fatigue crack propagation. The study results reveal that the turning of the subordinate peak is significantly associated with crack lengths and corresponds to strain gradient along the FBG. Meanwhile, the strain distribution sensed by the FBG changes with the sensing section of the grating. FBG sensors could observe the monotonic plastic zone ahead of the fatigue crack tip. The cubic strain is distributed along the grating, with monotonic plastic zone propagation at the initial and terminal part of the grating, at approximately a 30% ratio of the entire grating. However, the monotonic plastic zone is sensed by the FBG, at 15% bias of the grating center, with the quadratic strain gradient pattern along the grating. In particular, when the initial and terminal parts of the grating experience highly inhomogeneous strain distribution, the spectrum distortion occurs.