Straightness Evaluating Of Rail Factory Welded Joint On Railway Track

The railway industry standard "Welding of rails part 1: General specification"(TB/T1632.1?2014)stipulates that straightness of rail factory welded joints is accepted in the factory.The joints which meet the requirements of the standard are allowed to leave the factory.The straightness of welding joints on railway track may change generally.Some units measure the joints that did not need to be polished on railway track which leading to serious consequences.This paper investigates the straightness characteristics of rail factory welded joints in rails welding base;tracks and measures the straightness of the joints on railway track and summarizes the changing regulations.At the same time,this paper measures the straightness of rail base metal at a range of 6m around the joint,and reveals the characteristics of the straightness of rail base metal both on ballastless track and ballast track.On the basis of the measurement and research above,methods for evaluating the straightness of rail factory welded joints on the track are put forward.The main innovations are as follows:1.The peak value of the straightness of the top(driving surface)of the joint shows a downward trend,and the straightness of the working side(guiding surface)of the joint generally presents a tendency to proturde toward the center of the railway when the rail factory welded joints on railway track.2.Measuring the straightness of rail base metal at a range of 6m around the joint,we find that the driving surface of rail base metal will hunch up,and the arch camber of the ballastless track is higher than that of the ballastless track.The guiding surface of rail base metal will proturde toward the center of the railway,and the protruding value of the ballastless track is higher than that of the ballastless track.3.This paper considers the influence of track condition on measurement results when measuring and evaluating the straightness of rail factory welded joints on railway track.We correct the standard of the straightness of the joint,according to the straightness of the rail base metal near the joint.Four kinds of correction methods are proposed,which are extreme value method,average value method,effective mean value method and variation coefficient method.The risk of this four methods are also analyzed.The conclusion of this paper is that the straightness of rail factory welded joints should be checked and accepted at rails welding base according to the requirements of the railway industry standard(TB/T1632.1?2014).There is no need for "the second acceptance" on railway track.After measuring the straightness of rail factory welded joint on railway track,this paper recommends to use the variation coefficient method to evaluate the measurement results.