Research on Load Characteristics and Fatigue Damage of EMU Motor Bearing

The durability of bearings has always been a key problem in engineering. In recent years, more and more research has focused on the service safety of bearings used in railway vehicles. In this paper, taking the motor bearings on the trains of moving trains as the research object, establish the vehicle system dynamics model including the influence of transmission system vibration, so as to obtain the load characteristics of the cylindrical roller bearings NU210 and deep groove ball bearings 6016 in the motor under the working conditions of uniform speed straight line, different radius, and different superelevations of curves, etc., and then analyze the load characteristics of the bearings under different operating conditions. A damage methodology for motor bearing under random dynamic loads was developed based on the output loads of the vehicle dynamic model. The differences in motor bearing fatigue damage are compared under different operating conditions. The life of motor bearings under different lubrication conditions was predicted and compared. The results show that at the same speed, the standard deviation of force in each direction of bearing NU210 is small, while the standard deviation of force in each direction of bearing 6016 is large. Under the usual operating speed level, the viscosity ratio of bearing NU210 is between 3.1–3.26, while that of bearing 6016 is between 3.85–3.92. The viscosity ratio first increases and then decreases with the increase in vehicle speed, and the maximum viscosity ratio κ appears at the speed of 340 km/h. Regardless of the bearing mounting method, the damage per unit mile of each bearing in the motor must be greater in the curved condition than in the straight condition. The life evaluation of the bearing in the engine box of the EMU should be based on the 6016 bearings. If the reliability requirement is 99.5%, the life of 6016 bearings can guarantee service reliability during the replacement cycle. Some of the findings in this study will support maintenance programs for motor bearings and the design of high-reliability motor bearings.