无封装FBG应变传感器在不同布设方式下的标定试验研究

Experimental Study on the Calibration of Unencapsulated FBG Strain Sensors Under Different Mounting Methods

【目的】光纤光栅(FBG)应变传感器作为一种新型测量应变的仪器逐渐运用到土木工程领域中,其能运用的关键在于传感器的布设以及根据不同的使用要求和环境对灵敏度系数进行标定。为了确定表面直接粘贴和开槽植入两种光纤光栅应变传感器布设方法的测量精度。【方法】提出了一种用于沉桩试验的无封装FBG灵敏度系数的标定方法,并通过采用圆形无缝钢管作为基体对两种布设方法进行标定试验研究。【结果】在逐级加载阶段,开圆形凹槽植入粘贴法所得到的标定系数比表面直接粘贴更小,而表面直接粘贴法更接近理论值,开槽植入和表面粘贴法所得到的标定系数与理论值相比最大误差分别为2.84%和0.33%;在逐级卸载阶段,两种布设方法光纤的中心波长存在一定的滞后,但标定系数与加载阶段相差不大。【结论】在FBG使用过程中需要根据试验环境情况以及在试验允许误差范围内选择合理的光纤光栅布设方案及标定方法。

【Objective】As a new type of strain measuring instrument,fiber bragg gratings(FBG)strain sensors are gradually used in the field of civil engineering,and the key to their use lies in the deployment of sensors and the calibration of sensitivity coefficients according to different usage requirements and environments.The current conventional FBG installation methods are direct surface adhesion and slotting implantation.【Method】In order to determine the measurement accuracy of the two installation methods,a calibration method of the unpacked FBG sensitivity coefficient used for the pile sinking test was proposed and the calibration test of the two deployment methods was carried out by using the circular seamless steel tube as the matrix,and the calibration results were compared with the theoretical values.【Result】The results show that in the stage of progressive loading,the calibration coefficient obtained by slotting implantation is smaller than that by surface adhesion,while the calibration coefficient obtained by the surface adhesion is closer to the theoretical value.The calibration coefficients obtained by slotting implantation and surface adhesion were 2.84%and 0.33%respectively compared with the theoretical values;In the step-by-step unloading phase,there is a certain lag in the central wavelength of the two deployment methods,but the calibration coefficient is not much different from that inthe loading stage.【Conclusion】Therefore,it is necessary to choose a reasonable fiber grating layout scheme and calibration method according to the test environment and within the test tolerance range in the process of using FBG.