Rail Thermal Stress Monitoring Technology Based On Fiber Bragg Gratings

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 this paper, we research a track state monitoring system based on FBG with stable performance and high reliability for realizing the monitoring requirements of rail strain, temperature and temperature force. Meanwhile, we also design the packaging of FBG and explore the installation process.Firstly, we provide a brief introduction about the basic principle of FBG sensor in detection of temperature and strain. Furthermore, the cross sensitivity problems between temperature and strain is elaborated. Meanwhile, a novel strainmeter is designed for railway field.Secondly, based on the traditional one-dimensional model, the paper introduced the rail strain model and the measure priciple on the case of three-dimensional model. After that, the multi-parameter such as rail axial force and bending moment are measured by the three-dimensional model. In order to confirm the advantage of the model, we conduct a static load experiment to obtain rail axial force and curvature information.Finally, According to the CWR rail temperature force measure model, a bidirectional strain measure method which combines the axial and vertical stress measurement is proposed to overcome the problems that the CWR rail temperature force is usually difficult to measure. The new method gives solutions of both temperature compensation problems of FBG and the monitoring problems of CWR strain which due to temperature variety. Then we acquire the actual monitoring data and accomplish the validation of the theory model by installing the special packaged FBG sensors in Chengmianle high-speed rail line.