Brittle fracture of the composite insulator is a malignant accident. There is a lack of means to monitor the formation and expansion of stress corrosion cracking in rods, resulting in little understanding of the process of brittle fracture development. First, this article proposes a mechanical model for identifying cracks in rods by the wavelength shift trends of fiber Bragg gratings (FBGs). Second, several FBGs and FBG temperature compensation sensors are pasted on the 10-kV composite insulator rod’s surface. Then an optical fiber monitoring system for the brittle fracture process of the rod is established. Finally, the model and system were validated by conducting stress corrosion testing with different tensions. The results show that the surface quasi-distributed FBGs can monitor the temperature and stress in the complete brittle fracture process of a glass-fiber-reinforced polymer (GFRP) rod, which verified the correctness of the mechanical model for wavelength shift identification of cracks in axial cross sections. A temperature difference of 1 °C and the wavelength shift of the FBG on two or more fibers reach $1.1~\lambda _{s\mathrm {min}}$ and $0.9~\lambda _{s\mathrm {min}}$ can be used as warning thresholds for corrosive heat release, crack initiation, and rapid development of cracks to fracture, respectively. This article provides a quasi-distributed FBGs’ monitoring system and method to study brittle fracture of composite insulators in stress corrosion testing. It provides a technical means to evaluate and warn the mechanical properties of composite insulators.

中文翻译：

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准分布式光纤布拉格光栅监测复合绝缘子脆性断裂过程的系统与方法

复合绝缘子脆性断裂是一种恶性事故。缺乏监测棒材应力腐蚀裂纹形成和扩展的手段，导致对脆性断裂发展过程了解甚少。首先，本文提出了一种通过光纤布拉格光栅 (FBG) 的波长偏移趋势来识别棒中裂纹的机械模型。其次，将几个FBG和FBG温度补偿传感器粘贴在10-kV复合绝缘子棒的表面。然后建立了棒材脆性断裂过程的光纤监测系统。最后，通过在不同张力下进行应力腐蚀测试来验证模型和系统。结果表明，表面准分布FBGs可以监测玻璃纤维增​​强聚合物(GFRP)棒全脆性断裂过程中的温度和应力，验证了力学模型用于裂纹波长位移识别的正确性。轴向截面。1 °C 的温差和两根或多根光纤上 FBG 的波长偏移可达到 $1.1~\lambda _{s\mathrm {min}}$ 和 $0.9~\lambda _{s\mathrm {min}}$ 可分别用作腐蚀放热、裂纹萌生和裂纹快速发展至断裂的警告阈值。本文为研究复合绝缘子在应力腐蚀试验中的脆性断裂提供了一种准分布式光纤光栅监测系统和方法。它提供了一种对复合绝缘子的力学性能进行评价和预警的技术手段。