Development Of High Anti-fatigue Packaged Fiber Bragg Grating Strain Gauge

The significance of structural health monitoring manifest itself with the aging of civilengineering structures of importance and the development of structural intelligence.Fiber Bragg grating(FBG)strain gauges have become one of the main methods for structural health monitoring due to their excellent characteristics,and have been widely used in various fields.As the service time of engineering structures usually covers large time span,FBG strain gauges have to stay in good performance under long-term loading in order to achieve the structural full-life monitoring.At the same time,the fatigue reliability of FBG strain gauges is presently a key problem restricting its engineering application.In response,a high anti-fatigue packaged FBG strain sensor was manufactured in this paper,The strain gauge was encapsulated by GFRP.And then a clamp anchorage was used to clamping the GFRP central member to implement the static performance calibration and fatigue experiment of the strain gauges.Afterwards,the strain gauges are installed on the surface of the structure by means of the support welding,and the fatigue performance matching test is performed on the entire structure.The main research contents of this paper are as follows:(1)Development of high anti-fatigue packaged fiber Bragg grating strain gauge.Using GFRP material to encapsulate fiber Bragg grating as the center of strain gauge,and the clamped anchorage is used as the clamping member of the strain gauge where the new design concept of clamping piece is utilized to enhance the deformation compatibility of the clamping piece and to avoid the damage of the GFRP central member.The anchoring effect of this structure is verified by theoretical derivation,static load test and finite element simulation,and it is found suitable for application in strain gauge structure.The basic performance parameters of the strain gauge,e.g.range,linearity,sensitivity,repeatability,are determined with static tension test.The basic performance of the strain gauge is found good and hence suitable for engineering structure monitoring.(2)Investigate the fatigue performance of high anti-fatigue packaged fiber Bragg grating strain strain gauge.The fatigue resistance of the manufactured strain gauge under different working conditions was studied by accelerated fatigue test.The text results show that the performance parameters of the strain gauge can meet the requirements of long-term safety monitoring and the strain gauges have high fatigue resistance.The test data are fitted to formthe fatigue life curve,which provides a reference for predicting the residual life of the strain gauges and replacing the strain gauges.(3)High anti-fatigue packaged fiber Bragg grating strain strain gauge and structure fatigue performance matching test.With steel plate as the matrix structure,the manufactured strain gauge is mounted on structural surface by the welding installation method.And then the strain gauge and the structure subject to the action of fatigue together.It is verified that the strain gauge can maintain good performance before the structural fatigue failure,that is,full life monitoring can be achieved using the manufactured strain gauge.