Simulation Analysis And Monitoring Research On Stress Status Of Metro Rails

As an important part of urban transportation,metro has strong transport capacity and high efficiency,and plays an important role in the development of society.As an important part of metro track structure,rail plays a guiding and loading role in train running.Whether the train can run safely and smoothly depends on if the geometric shape of rail is normal.External load,temperature change and other factors often lead to rail deformation and internal stress,which will affect the safety of driving.The methods of manual inspection and periodic inspection of track inspection vehicles have the problems of low data density,low accuracy and poor real-time performance.In this paper,the rail temperature and longitudinal strain are monitored.A monitoring system of rail stress state is established,and the change of rail stress state is studied.The main research contents are as follows:Firstly,the mechanical characteristics of rails under the condition of subgrade deformation are studied,and the monitoring system of rail stress state is established.Using ABAQUS finite element software,the law between displacement load of subgrade and longitudinal strain distribution of rail is analyzed,and the layout scheme of monitoring nodes is determined.The monitoring node adopts the monitoring node-gateway-cloud server-client architecture.The hardware architecture and corresponding software workflow of the monitoring node and gateway are designed.At the same time,the software workflow of the cloud server is designed.The process of producing strain data of monitoring nodes and the factors causing errors in longitudinal strain measurement are analyzed,and the corresponding methods to reduce the errors are put forward.The test results show that the measurement errors of temperature and strain of the monitoring system are ±0.5℃、±3με,respectively.Secondly,rail mid-span positioning tool and strain gauge positioning tool are designed to reduce the position error when pasting strain gauge and improve the efficiency when pasting strain gauge.After field test,the angle error of strain gauge pasted with this positioning tool is less than 1 degree,the positioning error is reduced from ±5mm to ±1mm,and the time of positioning strain gauge is shortened from 2 minutes to 40 seconds,which improves the positioning accuracy and efficiency of pasting strain gauge.Finally,the temperature drift errors of the monitoring nodes under the condition of insulation and non-insulation of the bridge arm resistance are compared and studied.It is concluded that the temperature drift errors of strain measurement can be effectively reduced by adopting insulation measures for the bridge arm resistance,in which the temperature drift error is less than 1με/℃.In addition,four monitoring nodes are installed on the metro operation line to carry out monitoring tests,which verifies the ability of the monitoring system to operate normally in the Metro environment.The variation law of rail stress state is obtained by analyzing the temperature and strain data obtained by the monitoring system.