Research On The Key Technology Of Super Structure Fiber Bragg Grating Sensor For Rail Temperature And Stress Monitoring

Because of the elimination of a large number of joints,the seamless rail line has a series of advantages,such as smooth running,comfortable.With the development of high-speed railway and the continuous welded rail(CWR)widely applied,the status of the CWR has been becoming a rising problem for the safe operation of the railway.Since fiber Bragg grating(FBG)sensors can measure strain and temperature with high sensitivity,it became an emerging new application of railway safety monitoring.In order to solve the problems,this paper makes use of the advantages of track engineering technology,monitoring technology and optical fiber sensing technology.Based on the orbit dynamics and finite element analysis,the rail is simulated and analyzed.We propose a superstructure fiber Bragg grating sensing device for track condition monitoring,which can measure strain and temperature simultaneously.At last,the experimental results are analyzed and the relevant conclusions are obtained.The main contents and results are as follows:(1)The superstructure fiber Bragg grating sensing element is designed and fabricated by the point by point method.I-shaped sensor is a simple and convenient structure,which used as the substrate material of the sensor.By measuring the wavelength drift of the sensor element,the strain and temperature can be measured simultaneously,and the writing technique can achieve the sensitization effect due to the modulation of the refractive index of the fiber core.(2)In the laboratory tests on the sensing properties of super structure fiber Bragg grating sensor,the strain sensitivity coefficient is up to 2.2 pm/??,the highest temperature sensitivity coefficient is 17.92 pm/oC.The test results show that the response sensitivity of strain and temperature can be improved.(3)The laboratory model was used to test the performance of the superstructure fiber Bragg sensor which can monitor strain and temperature simultaneously.The optimal position of the rail structure strain monitoring sensor is determined by ANSYS finite element simulation and the influence of the high speed railway.The stress of the rail is simulated by the jack and the electric sensor,the rail is placed in the heating furnace to simulate the change of the rail temperature,and the wavelength drift of the sensor is measured under the influence of the rail strain and the rail temperature.The experimental results show that the design of the superstructure fiber Bragg gratings can realize the simultaneous measurement of the temperature and strain of the rail.