The Study Of Rail Longitudinal Stress Distribution Change

Recently, a large number of ballastless track structures have been used in passenger dedicated line in China. Although the possibility of rail breaking in high-speed railway is lower, because of the internal flaws in rail, they tend to grow and may eventually lead to rail break under the action of tensile stress, which endangers the safety of the railway. There is a far distance to large-scale practical application for traditional means of fault detection due to their inherent shortcomings. A new distributed rail stress monitoring technology and its wireless sensor network system based on stress method was developed and can transfer the real-time rail temperature and internal stress information to the customer. This thesis mainly studied the longitudinal stress distribution changes before and after the rail break by the way of finite element model combined with longitudinal stress distribution experiment.The structure of high-speed railway and the mechanical role of all its parts were researched. After classifying the various forces acting on the rail, the paper focused on the rail longitudinal stress and mainly studied the temperature force. And a qualitative analysis of rail longitudinal stress distribution before and after rail fracture was carried out then.Three-dimensional finite element model of ballastless rail is established using ABAQUS software and then the changes of rail longitudinal stress before and after rail break were simulated. The model calculation parameters, contact algorithm and model load were introduced. Different load steps were imposed to simulate rail break and calculate the rail internal longitudinal stress distribution changes.A rail longitudinal stress distribution experimental platform was built for verifying simulation results, which consisted of the rail device, the end fixtures, the temperature force simulation device and the sensor systems. The rail break experiments were carried out with preloading-and-then-releasing method and rail longitudinal stress changes before and after rail fracture are measured under three different conditions. After that, the simulation results of the three-dimensional finite element model and the experimental results were compared, which showed that the model could correctly reflect the distribution of the rail longitudinal stress. Also, the rail longitudinal stress distribution in some place was simulated and the high-speed rail internal longitudinal stress in this place in a period of time was given.