Dynamic analysis of ultra-low frequency carbody swaying for a high-speed rail vehicle: Causes and measures

This paper investigated on the ultra-low frequency carbody swaying (ULFCS) of a high-speed railway vehicle through field tests and numerical simulations. In the field tests, the vibration characteristics, the dynamics performance, the wheel-rail contact condition, and the track condition were analyzed to realize the manifestation as well as the possible cause of this abnormal vibration. The excessive low equivalent conicity caused by the abnormal wheel tread wear arouse suspicion for this issue. To find out the mechanism and propose the solving measures, the multi-body dynamic (MBD) model of the high-speed vehicle was developed and verified by applying the measured wheel/rail profiles and carbody acceleration. Based on the developed model, the linearized and nonlinear researches were performed. The results indicate that the carbody hunting, caused by the frequency coupling between the hunting mode and the carbody lower sway mode, is the deep reason of the ULFCS, and this issue can be solved by increasing the equivalent conicity and decreasing the roll stiffness of the anti-roll torsion bar. Furthermore, the ULFCS can pose a potential threat to running safety once the violent carbody swaying gives rise to the wheel-rail contact point entering the wheel flange area. Finally, the optimized measures that reducing the hardness of the abrasive block, changing the working mode of the tread cleaning device, and decreasing the anti-roll stiffness were proposed and verified by the on-track test.