光纤布喇格光栅器件应力疲劳评价理论研究

Investigation on Evaluation Theory of Fiber Bragg Grating Tensile Fatigue Property

光纤布喇格光栅器件应力疲劳特性严重影响着光纤光栅应变传感器的长期可靠性,为了评估光纤光栅器件的应力疲劳特性,分析了光纤光栅应变传感器的封装结构对疲劳评价的影响,并以表面直接粘接的简化模型评估了光纤光栅器件的应力疲劳特性.从简化模型的基本力学与光学特性出发,提出以光谱特性的边模抑制比和带宽作为评价光纤光栅器件疲劳的指标体系,以传感特性的灵敏度、线性度和应变传递效率作为评价粘接层疲劳的指标体系.设计了基于等强度梁的光纤光栅器件加速疲劳实验,疲劳的应力幅度为500微应变,频率为18赫兹;1000万次疲劳实验后,三支光纤光栅的带宽平均增加2.07%,平均应变传递效率和平均灵敏度分别下降4.5%和3.9%,实验结果说明提出的指标体系能有效地区分粘接层和光纤光栅的疲劳,从而验证了该评价理论的可行性.

Fiber Bragg Grating （FBG） tensile fatigue property seriously affects the long term reliability of FBG strain sensors. To evaluate FBG tensile fatigue property, the package of FBG sensors is analyzed, and the surface mounting FBG is selected to study the FBG tensile fatigue property. To distinguish the tensile fatigue signal of FBG from the bonding layer, the property of the grating reflection spectrum is proposed as the evaluation index of FBG, and sensing characteristics is proposed as the evaluation index of bonding layer. The grating reflection spectrum evaluation index includes side mode suppression ratio and the 3 dB bandwidth. And the sensing characteristics evaluation index includes sensitivity, linearity and the strain transfer efficiency rate. To verify this theory, an experiment based on equal strength beam is conducted, in which the amplitude of ＂AC＂ strain is 500 micro strains, and the frequency is 18 Hz. After 10 million tensile fatigue tests on three FBG sensors, the average bandwidth increase 2.07%, the strain transfer efficiency rate decrease 4.5 %, and the sensitivity decrease 3.9%. The experiment results show that this theory is workable.