Abstract
Wheel flat can cause a large impact between the wheel and rail and excites a forced vibration in the locomotive and track structure systems. The working conditions and fatigue life of the motor bearings are significantly affected by the intensified wheel–rail interaction via the transmission path of the gear mesh. In this study, a fatigue life prediction method of the traction motor bearings in a locomotive is proposed. Based on the L−P theory or ISO 281 combined with the Miner linear damage theory and vehicle–track coupled dynamics, the irregular loads induced by the track random irregularity and gear mesh are considered in this proposed method. It can greatly increase the accuracy of predictions compared with the traditional prediction models of a rolling bearing life whose bearing loads are assumed to be constant. The results indicate that the periodic impact forces and larger mesh forces caused by the wheel flat will reduce the fatigue life of the motor bearings, especially when the flat length is larger than 30 mm. Using this method, the effects of the flat length and relatively constant velocity of the locomotive are analyzed. The proposed method can provide a theoretical basis to guarantee safe and reliable working for motor bearings.
Highlights
Wheel flat is a typical form of wheel tread failure, which continually occurs during the operation process of a high−power locomotive, owing to the emergency braking and skidding phenomenon of the wheelset
As a common fault of the wheel, a wheel flat can generate a periodic impact at the wheel–rail contact area and significantly intensify the wheel–rail interaction, which is induced by emergency braking or skidding idling
By using L − P theory by using ISO method where Li and Lo are fatigue life in millions of inner race revolution based on the contact loads of inner and outer races, respectively; Pi, Po, and PISO are the corresponding equivalent bearing loads, which can be extracted from the simulation results; a1 and aISO are the life correction factor for the reliability and the coupled influence of lubrication, contamination, and fatigue load limit of the material, respectively; Ci, Co, and CISO are the basic dynamic loads acting on the inner race, outer race, and the rolling bearing, which can, respectively, be calculated as
Summary
Wheel flat is a typical form of wheel tread failure, which continually occurs during the operation process of a high−power locomotive, owing to the emergency braking and skidding phenomenon of the wheelset. The larger periodic impact forces induced by the wheel flat can intensify the system vibrations, cause failure and fatigue damage of the components in a locomotive, such as the traction motor bearings, and even endanger the locomotive and track structure systems [1]. Previous investigations on this topic have focused on the wheel–rail interaction and the effect of wheel flat on the dynamic behaviors of the vehicle/track structure. It is essential to investigate the instantaneous fatigue damage of the motor bearing considering the effect of time−varying loads based on the dynamic simulation and further prediction of its reliable service life. The results of the analysis can reflect the damage of the wheel flat on the operational reliability for the traction power transmission of the locomotive
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