Research On Wheels Ellipse Problems Of Subway Vehicles

Based on the problems existing on certain subway line2, in vehicles system dynamics point of view, researches are carried out on the phenomena of easy wheel tread spalling, wheel ellipsation and severe vertical vibration of car body.Aim at the phenomenon of bad vertical dynamic behavior of the subway line 2 vehicles, comprehensive analysis has been carried out on the vehicle dynamic behavior. And optimization has been performed on the critical parameters relating to the wheel ellipsation(the main estimation index is the longitudinal vibration of wheels) and vehicle vibration. The two main parameters are: composed longitudinal stiffness of traction device and composed lateral(and longitudinal) stiffness of first suspension. Dynamic analysis shows that, when there is vertical shock excitation, short traction rod makes the vertical vibration acceleration of vehicle end increase about 50% in comparison to the case of long traction rod or without traction rod; when sudden braking or traction is applied on vehicle, short traction rod also makes vibration acceleration of vehicles increase significantly. Since frequent and long term braking is applied on subway vehicles, vertical vibration of vehicles often keeps high level. The calculation results are the theoretical evidences to use the localized devices to reduce the wheel ellipsation problem of The subway line2. The two solutions are considered critical to solve the problems.On line2 the wheel ellipsation problem is associated with the big vertical vibration, i.e. as for line2 vehicles, small ellipse on wheel will increase vehicle vibration, and increased vehicle vibration will make wheel ellipse develop furthermore, and leads to frequent wheel reprofiling. So what's important is to reduce the association level. The calculation result can not yet provide direct evidence to approve that the wheel out-of-roundness is caused by short traction rod, nor to avoid the association between them, but the negative influence of big connection stiffness of short traction rod is obvious.