Research On Stress-free Temperature Detection Technology Of Continuous Welded Rail

When the actual stress-free temperature of the continuous welded rail is greatly offset from the construction stress-free temperature,since the rail cannot be freely stretched,a large temperature stress will be generated inside the rail,which will affect the reliability and stability of the rail.In severe cases,a broken or expanded rail will occur.The rapid and accurate detection of the actual stress-free temperature of the continuous welded rail has been the focus of scholars at home and abroad.This paper has discussed the basic theory of continuous welded rail,the basic knowledge of ferromagnetism and the generation mechanism of magnetic Barkhausen noise(MBN)signals.By analyzing the influence of rail stress on MBN signals,the construction and calibration of MBN stress detection system has been realized.Through the study of the continuous welded rail which is in service in the Baoding Track Maintenance Division of China Railway Beijing Group Co.Ltd,the suitable temperature stress detection point on the rail has been found.In theory,the residual stress distribution of the rail head and the rail waist center has been analyzed.The MBN stress detection system has been used to detect the temperature stress of the track head and the rail waist center.By analyzing the data,it has been found that the rail waist center is more suitable as a detection point.The reason for the actual stress-free temperature attenuation has been analyzed.The MBN technology has been used to detect the actual stress-free temperature of the researched railway,and combined with the the researched railway’s history data of the stress-free temperature,it has showed that the actual stress-free temperature of the researched railway has been in attenuating trend.Finally,the least square support vector machine(LS-SVM)algorithm has been proposed to establish the regression model of the relationship between rail temperature stress and the difference between the rail surface rail temperature and the actual stress-free temperature.The actual stress-free temperature of the rail has been obtained by using the regression model,the temperature stress at each point of the rail and the surface rail temperature.The rail temperature stress and surface rail temperature have been tested on another continuous welded rail of Baoding Track Maintenance Division,which has verified that the detection method is more efficient and accurate,and it has improved the detection accuracy.