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利用裸光纤布拉格光栅测量结构物表面应变,基于光纤层-胶结层-基体层的应变传递模型,从理论上分析了预张拉对应变传递率的影响,并通过实验进行了验证。利用预张拉光栅与未预张拉光栅同时测量了等强度梁正反两面的应变。实验中为排除黏贴长度及厚度的影响,采用LOCTITE点胶机控制滴胶量,得到应变随荷载变化的曲线,并与等强度梁理论应变值进行对比,得到应变传递率与荷载的关系曲线。结果表明,在测拉应变时,预张拉光栅的应变传递率高于未预张拉光栅的应变传递率,且两者都在96%以上;在测压应变时,预张拉光栅的应变传递率低于未预张拉光栅的应变传递率,且两者均在95%以上,与理论分析相符。这说明对测拉应变的实验,预张拉能提高应变传递率;而对测压应变的实验,预张拉会降低应变传递率。
Using the fiber Bragg grating to measure the surface strain of the structure, the influence of pretension on the strain transmissibility is theoretically analyzed based on the strain transfer model of the fiber layer-cementation layer-matrix layer, and verified by experiments. Using the pre-tensioned grating and non-pre-tensioned grating, the strain of the positive and negative surfaces of isosceles beams was measured simultaneously. In order to get rid of the influence of the length and thickness of the adhesive, the LOCTITE dispenser was used to control the amount of glue. The curve of the strain with load was obtained and compared with the theoretical strain of the equal strength beam. The relationship between the strain transfer rate and the load was obtained . The results show that the strain transfer rate of the pre-tensioned grating is higher than that of the non-pre-tensioned grating at the time of tensile strain measurement, and both of them are above 96%. When the strain is measured, the strain of the pre-tensioned grating The transmission rate is lower than that of the non-prestressed grating, and both are above 95%, which is consistent with the theoretical analysis. This shows that the tensile strain test, pre-tension can increase the strain transfer rate; and the test of the compressive strain, pre-tension will reduce the strain transfer rate.