Research On Dynamic Behavior Of Axle Box Bearings Of High-Speed Trains

As a key component of the train, the axle box device implements the connection and transfers the relative motions and interaction forces of the wheelset and the bogie frame. The rolling bearings assembled in the axle boxes, which called axle box bearings, are the main elements of the axle box devices. Their working status has a significant impact on the performance of the high-speed trains. With the progress made in the design and manufacture technology of locomotives and vehicles, the operating speed of the passenger trains has been improved remarkably. The China Railway High-speed (CRH) trains now can reach a top speed of 300 km/h while operating. The increase of the train’s speed makes the operating conditions of the axle box bearings more critical. With the increase of the bearing speed, the contact and collision between the bearing components will become more severe, the bearing elements will rotate more irregularly and more thermal will generate. More seriously, while operating on the railway, the high-speed train will always suffer the track irregularity excitation inevitably and hence vibrate erratically. In the vibration environment the forces and movements of the axle box bearings’ components can be more irregular, which can have an obvious influence on the axle box bearings’ dynamics performance. Whether the high-speed train’s key components can maintain good performance in the harsh operating conditions has a great impact on the operating property of the train.The dynamics behavior of the axle box bearings of the high-speed trains is researched in this paper. The main contexts of the thesis are summarized as below:The dynamics model of the axle box bearings of the high-speed trains is established. Firstly, the constraints of the bearing components are determined according to the fit relations of the bearing with the axle box and the axle of the high-speed train. The forces and motions of the bearing components are then analyzed. A judgement model of the contact status between the components is established based on their centroids’displacements and geometric characteristics. The contact deformations are then calculated with the model. A calculation model based on Hertz contact theory is established to compute the contact forces between the bearing components. The tangential component of the two components’ relative velocity at their contact point is calculated to determine whether relative sliding movement occurs and hence compute the sliding friction between them if it does occur. Finally, the differential equations of motion of the axle box bearings are obtained.A calculation program based on 4/5 order Runge — Kutta method was compiled in FORTRAN 2011 to solve the above differential equations. The dynamic behavior at the start-up phase of the axle box bearings withstanding a greater radial load, a driving force and a driving torque is analyzed. The result indicates that the centroid of the inner ring fluctuates around the equilibrium position, the orbital motion radius of the roller’s centroid has a variation range, and the cage turns out to whirl. The visualization of the calculation results were implemented in MATLAB.A dynamic model of the axle box bearing of high-speed trains is established based on a three-dimensional dynamic simulation software specifically for rolling bearings. A dynamic simulation of the high-speed train is executed to acquire the external loads acting on the axle box bearing while the train is operating. A comparison of the contact forces and stresses between the bearing components and the cages’ motion stability under the two working conditions:the track irregularity is taken into consideration and the track irregularity isn’t considered is executed to analyze the influence that the track irregularity impacts on the high-speed train’s axle box bearing. It is concluded that with the excitation of the track irregularity, the contact forces and stresses between the raceways and the rollers in the two different rows show a significant difference. The maximum value of the contact stresses between the rollers and the raceways are obviously greater while considering the track irregularity. However, the excitation of the track irregularity has little effect on the motion stability of the cages’ centroids.