Evenness improvement method for high-speed turnout crossing areas

In this study, an evenness improvement method for new high-speed turnout crossing areas is proposed for the development of high-speed turnout and amplification of the wheel-rail dynamic impact in the crossing areas. A dynamic analysis model of the vehicle-turnout coupling system is established. In this model, the stock and switch rails as well as the wing and point rails are independent units. These independent units are connected using spring-damper units with variable parameters to accurately simulate the wheel-load transition process and the dynamic characteristics of the turnout. On this basis, an optimized scheme is developed for point rail-wing rail matching based on the center-of-mass oscillation compensation of wheelsets, and the rationality of the optimization method is verified via dynamic simulation evaluation at a high speed. Finally, the proposed method is validated through indoor actual-scale tests. The following are the results of this study. (1) As the vehicle passed over the crossing under the existing design scheme, the center-of-mass oscillation reached an oscillation length of 1.16-1.52 mm such that lifting the wing rail alone failed to eliminate the center-of-mass oscillation of the wheelsets. This is because the point and wing rails were incorrectly matched, leading to a backward shift in the wheel-load transition, thus causing a sharp drop of the wheelsets. Together with wing rail lifting, the longitudinal slope matching of the point rail effectively retained the wheel-load transition characteristics under the existing design scheme and eliminated the center-of-mass oscillation of the wheelsets. (2) As the train passed through the turnout crossing at a high speed, the optimized scheme substantially reduced the center-of-mass oscillation of the wheelsets, wheel-rail dynamic impact, and axle-box vibration while ensuring consistency of the wheel-load transition characteristics with the existing design scheme. (3) The maximum deflection change rate of the wing rail in the assembled crossing was only 1.67 mm/m, which could not meet the requirement of the theoretical longitudinal curve, and would cause the problem of turnout sleeper lifting, affecting the precision of laying turnouts on-site. Computer numerical control machining should be used to achieve the longitudinal curve requirement of the wing rail. The iron plate thickness should be increased gradually to 0.5 mm from the #82 sleeper to the #86 sleeper. Accordingly, the amount of machining of the wing rail should be increased from 0 mm to 2 mm. At the #92-#95 sleepers, this amount of machining should be decreased from 2 mm to 0.6 mm and then increased to 2 mm. This process would accurately realize the theoretical longitudinal slope curve.