Crack damage detection for aluminum alloy materials using fiber Bragg Grating (FBG) sensor is a kind of structure health monitoring. In this paper, the damage index of full width at half maximum (FWHM) was extracted from the distorted reflection spectra caused by the crack-tip inhomogeneous strain field, so as to explain the crack propagation behaviors.,The FWHM variations were also investigated through combining the theoretical calculations with simulation and experimental analyses. The transfer matrix algorithm was developed to explore the mechanism by which FWHM changed with the linear and quadratic strain. Moreover, the crack-tip inhomogeneous strain field on the specimen surface was computed according to the digital image correlation measurement during the experiments.,The experimental results demonstrated that the saltation points in FWHM curve accorded with the moments of crack propagation to FBG sensors.,The interpretation of reflected spectrum deformation mechanism with crack propagation was analyzed based on both simulations and experiments, and then the performance of potential damage features – FWHM were proposed and evaluated. According to the correlation between the damage characteristic and the crack-tip location, the crack-tip of the specimen could be measured rapidly and accurately with this technique.

中文翻译：

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使用 FBG 传感器通过损伤特征 FWHM 检测疲劳裂纹扩展

利用光纤布拉格光栅（FBG）传感器对铝合金材料进行裂纹损伤检测是一种结构健康监测。本文从裂纹尖端不均匀应变场引起的畸变反射光谱中提取半高全宽(FWHM)损伤指数, 以解释裂纹扩展行为。将理论计算与模拟和实验分析相结合。传输矩阵算法的开发是为了探索 FWHM 随线性和二次应变变化的机制。此外，根据实验过程中的数字图像相关性测量，计算了试样表面的裂纹尖端非均匀应变场。实验结果表明，FWHM曲线中的跃点与裂纹扩展到FBG传感器的时刻一致。,基于模拟和实验分析反射谱变形机制与裂纹扩展的解释，进而分析潜在损伤特征的表现– 提出并评估了 FWHM。根据损伤特征与裂纹尖端位置的相关性，该技术可以快速准确地测量试样的裂纹尖端。