涂覆层对光纤布拉格光栅应变传递的影响机理分析

Mechanism analysis on the impact of coating to fiber Bragg grating strain transfer

利用光纤布拉格光栅(FBG)测量结构物表面的应变时,FBG的涂覆层会对其应变传递产生影响,从而造成测量结果与真实应变之间有较大的差异。针对此问题,建立了应变传递模型对有涂覆层和无涂覆层两种FBG应变传递率进行了理论分析,得出了两者的平均应变传递率随粘贴长度的增大而增大。为了验证理论模型的适用性,进行了等强度梁实验,实验结果表明在相同的粘贴长度下有涂覆层FBG的平均应变传递率较低,且其最大平均应变传递率仅能达到92%,而无涂覆层FBG在粘贴长度达到6 cm时,应变传递率已经可以达到99%,可以满足绝大多数的应变测量需求。所建立的应变传递数学模型与实际的试验验证结果相符,深刻揭示了涂覆层对FBG应变传递率的影响规律,为FBG应变测量的工程应用提供了重要的参考。

To measure the surface strain of structure using fiber Bragg grating （FBG） sensor, the coating of FBG will affect its strain transfer, and bring the difference between the measured and the true strain. To solve this problem, the strain transfer model is built to analyze the strain transfer rate of coated and bare FBGs. The theoretical analysis indicates that the average strain transfer rate increases with the increased bonding length. In order to verify the applicability of the theoretical model, this study designs equal strength beam experiment. The experimental results show that the average strain transfer rate of coated FBG is lower than bare FBG＇ s for the same pasting length. The maximum average strain transfer rate of coated FBG is 92%. While the bonding length of bare FBG reaches 6 cm, the average strain transfer rate is over 99% , and can meet most demands of the strain measurement. The strain transfer model is consistent with experimental results, proving the influence of coating on FBG＇ s strain transfer rate, and providing an important reference for engineering applications of FBG strain measurement.