Frequency Analyses in Railway Vehicle Dynamics Simulation

摘要

High level of vertical acceleration vibration, which was far beyond specification requirements for one locomotive equipped with radial bogie, was measured in track testing. The result of the track testing indicates that it has good lateral and curve negotiating performance. But its vertical vibration acceleration reaches a high level. According to this problem, frequency components from tests are compared with the results of simulation in detail. However, the results of regular nonlinear calculation in time domain show that its vertical dynamical performance should be excellent. It's a more nervous problem because the track tests show the vertical dynamic of the locomotive is much worse. Based on the study of parameters in suspension and bogie structural characteristics, it is confirmed that the problem is caused by the arrangement of the braking unit, which is mounted on steering beam and the primary longitudinal stiffness of the middle wheel-set in suspension. When the wheel-sets are under the vertical impact of rail gap, the friction coupler of the equipment can't slide smoothly. Thus makes the rigid joint come into being at the ends of the primary vertical suspension, causing the abnormal vertical vibration of locomotive. Analyses based on a simple model, show that friction coupler between the braking unit and the axle box will cause a 6 Hz car-body response peak. The trend results the 8.4 Hz car-body which is bending with modal vibration dominated in frequency response during track testing. It is expected to reduce the greater response 8.4 Hz. It can be obtained from track testing if the friction coupler is removed. There are two methods used in railway vehicle dynamics simulation commonly. One is the linear frequency analyses; the other is the non-linear calculation in time domain. Among them, the time of the linear frequency analyses method is quite shorter than the non-linear calculation. And using the former can make a judgment of the function of the system quickly. Moreover, in some cases, we can't get a real analysis if we only take the non-linear calculation method in time domain. Through the linear frequency analyses, we can know much more of the manifestation in its essence than the nonlinear method. So when carrying the response analyses in the suspension system of the railway vehicle, we should adopt the linear frequency analyses first, for the non-linear analyses has some chanciness, and it can't representation the characteristics of the system.