Dynamics and vibration analysis of a vehicle with inner axle box based on flexible wheelsets

This study systematically investigates the dynamic performance and vibration characteristics of a metro vehicle equipped with an inner axle box bogie, with a focus on the effects of wheelset structural flexibility. A rigid-flexible coupled dynamics model is constructed. For computational efficiency, the flexible wheelset within it was developed using the finite element method and subsequently condensed via substructuring techniques. The model is integrated into multi-body dynamics software SIMPACK, incorporating non-linear suspension characteristics. Parametric analysis is conducted to evaluate vehicle dynamics under varying primary vertical stiffness and operating speeds, comparing rigid and flexible wheelset configurations in terms of straight-line ride comfort, non-linear critical speed, and curve negotiation safety. The influence of wheelset flexibility, evaluated through time- and frequency-domain analysis of axle-box vibration, is found to be subtle yet statistically relevant: it slightly reduces critical speed and amplifies lateral vibrations at high speeds without inducing resonance or exceeding safety thresholds. The rigid wheelset model is deemed sufficient for basic curve negotiation and vibration analysis, whereas the flexible model is recommended for critical speed and high-speed dynamics. These findings provide theoretical support for the design and optimisation of inner axle box bogies.