Analysis of vibration characteristics of axle-box bearings in urban rail vehicles under internal and external excitation coupling

Axle-box bearings are essential for urban rail vehicles, and obtaining their vibration characteristics during practical running is crucial for vehicle safety and stability. In this paper, considering flexible wheelsets and axle-box bearings, a rigid-flexible coupled dynamics model of a metro vehicle with track irregularity is established using SIMPACK. The bearing is simplified as an inner race and an outer race, and rollers are equivalent to several force elements. Bearing early fault and wheel-polygonal wear are established for simulation, to research axle-box bearing vibration characteristics under internal and external excitation coupling. Results show that, the wider the bearing defect, the more intense the bearing vibration and the greater the maximum roller contact load. Wheel-polygonal wear of 24 similar to 57th orders causes resonance in the bearing system. Within resonant order range, the bearing vibration is severe and more influenced by wheel-polygonal wear. At non-resonant orders, bearing internal faults have a more significant impact. At lower speed, the bearing fault signals are more obvious. On the contrary, at higher speed, excitation signals such as track irregularity and wheel-polygonal wear are more prominent, even submerging fault signals and causing interference to bearing early fault detection.