Numerical study on the ratcheting performance of heavy haul rails in curved tracks

Abstract

The ratcheting performance of heavy haul rails in curved tracks under different in-service loading conditions was numerically evaluated by using a recently developed approach. The wheel–high rail cyclic rolling contact was simulated by translating the non-Hertzian contact pressure distribution and the estimated longitudinal tangential traction repeatedly on the running surface of the high rail. The maximum ratcheting strain rate of the rail target section was obtained in each loading cycle. Based on the known ductility limit of the rail steel and the obtained maximum stabilized ratcheting strain rate, the crack initiation life of the rail was predicted in each case. The results indicate that the crack initiation life for all the three rail steel grades investigated decreases with the increase of the tangential traction coefficient, the friction coefficient, the ratio of lateral/vertical load and the axle load. Under the same in-service loading conditions, the ratcheting performance of the rails in curved tracks is worse than the one in tangent tracks. For instance, the crack initiation life of the low alloy heat-treated steel installed in the high rails is reduced by approximately 80% with the axle load of 35 t, the lateral/vertical load ratio of 0.3, the friction coefficient of 0.4 and the tangential traction coefficient of 0.5. The hypereutectoid steel rail with a lower carbon content always shows the best ratcheting performance and is likely to be the most reliable choice for the high rails in curved tracks. Moreover, the crack is predicted to initiate around 1 mm beneath from the top initial contact point. As the traction conditions become more severe, the location of crack initiation will shift from the subsurface to the running surface. The results can provide valuable information to assist rail operators in the selection of rail steel grades and the development of rail maintenance strategies.