Research On The Key Technologies Of Prolonging The Service Life Of Heavy-haul Turnouts

The track equipments, especially for turnouts, are confronted with serious challengewith the increased axle load and traffic. The curved switch rails and frog for heavy haulturnout get worn and defected more quickly, last shorter and need to be replaced frequently,which on the one hand results in huge pressure on the maintenances work and on the otherhand interrupts normal railway operation, becoming a barrier for heavy haul development.This paper focuses on approaches to prolong the lives of these rails. Based on the existingresearch achievements as well as the state and MOR projects, the key technologies used toextend the service lives of heavy haul turnout and its components are systematicallyelaborated. Those key technologies are also verified by the trial-manufacture andtrial-operation of the No.12turnouts for27t axle load application on Datong-Qinhuangdaoline and30t axle load on Shuohuang line. The main contents are as followsNo.12No.12:（1）The application and structural features of heavy haul turnouts in foreign countriesare analyzed and critical technologies for extending the life of turnouts are studiedsystematically. The theoretical studies, structure design and application of heavy haulturnouts in China are also investigated. Statistical analysis has been made for the servicelives of switch and frog rails. Major factors influencing the lives of switch and frog rails areconcluded and core issues and basic principles which shall be taken into account inimproving the technology of heavy-haul turnouts are proposed.（2）NUCARS is applied to establish the dynamic vehicle/turnout coupling modelfor30t axle load.The model is validated by comparison with test data. The simulation result is used tooptimize the structure design.（3）The switch rails with tangent-curved layout is studied and tested in field. The wearcharacteristics of traditional curved switch rails are analyzed and causes that shorten theservice life of switch rail are explored. Since experience has shown that straight switch railsare more wear-proof, it is suggested that the straight end of switch rails be extended toprolong the lives of these rails and improve the rail’s wear performance. The proposed newswitch rail applies an offset and half-intersecting profile and the offset (distance from the curveto the straight line) is increased to40.8mm. The curve starts where the width of rail head is66.8mm and the tangent section of switch rail is5439mm long, which is two times of that of traditional switch rails. The simulation results show that such design can significantly reducethe wear as well as the lateral force acting on the front end of switch rail so that the switchrail’s wear performance can be improved and service life extended.（4）The switch rail is widened by decreasing the width of stock rails. Computationanalysis is done via the heavy haul vehicle/turnout model and the optimal solution is figuredout according to lateral wheelset displacement, vertical force, lateral force, wear and otherparameters. Structural parameters for the No.12turnout, such as the maximum amount ofstock rail to be cut off, start and stop locations for cutting, depth of switch rail toes and widthof rail head200mm from the toe of switch rail, are determined given that safety of trainspassing the turnout are assured. The No.12turnouts with the above-mentioned features arelaid on the Datong-Qinhuangdao railway for their wear and life test. The severest wear isfound where the switch rail is60-70mm wide, a different wear characteristics comparingwith that of traditional rails and life of the new switch rail is3to4times of that of traditionalones.toeNo.12（5）Based on optimized wheel/rail interaction, the reducing value for nose and liftvalue of wing rail are designed and verified in test. A number of wheel treads oflocomotives and wagons operated on Datong-Baotou and Shuohuang railways aremeasured and a fitting tread is developed by using the measurement data to instruct the frogdesign. According to the simulation results, the raising value of wing rails and reducingvalue of frog noses are optimized taking into consideration the requirements of both theLM tread and fitting tread. The new type of frog is tested on the Datong-Qinhuangdaorailway and test data has shown that the nose and wing rails are in good interaction andpresent expected wear performance.（6）The running surface profiles of frog nose and wing rails are optimized and tested.The top surface profiles of the frog nose and wing rails have been redesigned according tothe wheel/rail optimized interaction. After Optimization, the contact stress can be reducedby54%and the wear of both frog nose and wing rails can be reduced as well in early stageof frog application.（7）The technique for frog nose widening is studied and tested. Based on the principlesand equations for calculation of frog parameters as well as wheelset dimensions andtolerances for locomotive and wagons in China, new parameters for check gauges between the frog, guard rail and other components are proposed, especially the check gauges for thefixed frog are modified. Long-term test has varified the rationality of recommended frogparameters. Frog with heavy nose is also designed based on the above parameters. The nosemay have the support area of its head segment10mm to40mm wide increased by32%.Simulation analysis for the frog parameters and nose widending technique also show theyare safe and feasible. Many sets of turnouts with widened frog nose are laid on Shuohuangrailway and Miniprof is used to monitor the wear and life performance of the frog nose andwing rails for a long term. Test results have shown that the widened frog nose can help toextend the service life of nose remarkably.（8）The No.12single split turnouts with60kg/m and75kg/m rails and fixed frogs aredesigned and manufactured according to the simulation results and two sets of each type arelaid on the Datong-Qinhaungdao and Shuohuang railways for30t axle load test, especiallyfor monitoring of the performance of switch rail and frog. By comparing the new turnoutswith traditional ones, the role of optimization technologies and related design in prolongingthe service lives of both curved switch rail and fixed frog is confirmed.