Straightness Optimization Research On Rail Welded Joint Of High Speed Railway

The straightness of welded joints of high-speed railway rails is one of the important indicators to ensure the smoothness of seamless lines.In order to further study the influence of straightness of rail welded joints on the operation of high-speed trains,and further optimize the rail straightness of weld joints,two test sections of the track are to be laid in the Beijing to Shenyang high-speed railway.The length of each test section is 10 kilometers.In the two test sections,according to the railway industry standard control the top surface straightness of the welded joints at the range of near upper limit and near lower limit.In the case of meeting existing standards,control the straightness of weld joint precisely,it does not involve any changes of the existing standards.Test section(I):At the welding base,100 meters long rails are welded into 500 meters long rails,there are totally 160 base welding joints laid on the test section(I).The top surface straightness of the joints are controlled at 0.1mm to 0.15mm.In the construction site,there are 40 site welding joints welded by mobile flash welding.The top surface straightness of the joints are controlled at 0mm to 0.1mm.Test section(II):At the welding base,100 meters long rails are welded into 500 meters long rails,there are totally 160 base welding joints laid on the test section(?).The top surface straightness of the joints are controlled at 0.25mm to 0.30mm.In the construction site,there are 40 site welding joints welded by mobile flash welding.The top surface straightness of the joints are controlled at 0.1mm to 0.2mm.Using the high-speed comprehensive detection trains to collect the data by shuttle run in Beijing to Shenyang high-speed railway,choose the acceleration data of the axle box on the vehicle at different speed levels in two test sections and contrast sections,draw the axle box acceleration mileage diagram,and estimate the position of the welded joint by marking the peak value of the waveform within 100 meters in the diagram to study the influence of the straightness of rail welded joints on vehicle dynamics.The conclusion of this paper as follows:1.After the base welded joints welding at the welding base layout,affected by the transportation process,line conditions and rail fasteners,the straightness of the top surface of the welded joint has settled.The settlement of test section(I)is about 0.05mm,and the settlement of test section(II)is about 0.15mm.It was found that the higher the straightness of the welded joint to be,the greater the settlement to be.2.Estimate the position of the welded joint in the axle box acceleration mileage diagram,then choose the peak and calculate the mean,we found that the average value of the vertical acceleration of the axle box at the location of the welded joint in the test section(?)is 2.3696 g,the average value of the vertical acceleration of the axle box of the welded joint in the contrast section was 2.4348 g,the value in test section is lower than the contrast section 0.0653g.It was found that by analyse the data of the straightness of base welded joints outside the test section,the straightness of base welded joints before delivery is basically controlled at 0.15mm to 0.2mm,is closed to the lower limit standard used in test section(?).Therefore,the difference between the average vertical acceleration of the axle box of welded joints in the test section(?)and the contrast section may not be significant.3.Estimate the position of the welded joint in the axle box acceleration mileage diagram,then choose the peak and calculate the mean,we found that the average value of the vertical acceleration of the axle box at the location of the welded joint in the test section(?)is 2.3615 g,the average value of the vertical acceleration of the axle box of the welded joint in the contrast section was 2.2552 g,the value in test section is higher than the contrast section 0.1063g.4.Through the axle box acceleration mileage diagram,we found that the smoothness of the curve in the test section(?)using the near lower limit standard is better than contrast section,but the difference is not obvious.The smoothness of the wave in the test section(?)using the near upper limit standard is worse than contrast section.Under the premise of ignoring the difference of line conditions,showing by the axle box acceleration mileage diagram,the smoothness of the curve in the test section(?)using the near lower limit standard is better than the test section(?)using the near upper limit standard.Therefore,it is recommended that the straightness of base welded joints should be controlled near the lower limit of standard currently used.5.At the speed of 200km/h to 300km/h,with the increase of speed grade,the axle box acceleration curve did not show more severe fluctuations,by calculate the mean of joints,the vertical acceleration value of the axle box at the location of the welded joint also did not show a significant increase.6.Showing by the axle box acceleration mileage diagram,the area where the fluctuation of the curve fluctuates greatly shows that the position of the welded joint cannot be clearly found.It is speculated that the irregularities caused by the track conditions or base material defects,so this kind of irregularities are more serious than the irregularities caused by welded joints.