Abstract:

Due to the complexity and randomness of the loadings that are endured by electrical multiple unit (EMU) axle boxes, actual on-rail measurements for a certain type of EMU motor bogie axle boxes are taken in addition to the measurements of loadings on axle box springs and tumblers. The springs and tumblers loading time histories on a representative rail route as well as the vehicle running speed information are obtained. Based on ISO standard method and studied the life prediction method of axle bearings in combination of damage, the complex loading characteristics for EMU axle box bearings are analyzed, a method to approximately transform tumblers’ loadings into the radial and axial loadings for the bearings is proposed. The predicted lives for axle box bearings at different reliability levels under actual complex vehicle running loadings are calculated and compared with the life obtained under conventional ISO standard method. Results show that the predicted life under proposed method is more conservative and safe comparing to the life calculated using ISO method. In addition, the fatigue life of axle box bearings during low-speed enter/exit warehouse event loadings is calculated and found to be much shorter than the life during high-speed running loadings. This phenomenon, which are to be studied from the damage point of view, indicated that the damage per kilometer caused by low-speed enter/exit warehouse event on axle box bearings is much bigger than the damage caused by high-speed running on rail. Last but not the least, this paper provided the predicted life for axle box bearing under different loading percentages and results have proven the reasonableness of this proposed life prediction method. The proposed method could serve as a guideline for designing high speed EMU train axle box bearings and conducting relevant theoretical studies.

Key words: actual measured loadings, axle box bearing, damage, life prediction, EMU