Effect of moderating friction of wheel/rail interface on vehicle/track dynamic behaviour

Lubrication in sharp curves has been commonly adopted so far to decrease the friction between wheel flange and rail gauge face following wear reduction and energy consumption. Also, lubrication is focused on its effect on decreasing the possibility of wheel flange climb derailment and squealing which is a kind of rolling noise. In addition, the lubrication between wheel tread and the top of low rail is studied to prevent low-rail corrugations in sharp curves. The lubricant supplied between the top of rail and wheel tread called “friction modifier” because of its traction characteristics, the relation between traction coefficient and slip ratio, modified to be suitable for refraining negative damping or sliding between wheel and rail has recently been developed. In this study, track site measurements were carried out to identify the effects of lubrication between wheel tread and the top of low rail, and between wheel flange and the gauge face of high rail on vehicle/track interaction excited by vehicle running in sharp curves such as lateral force and the angle of attack caused by a leading axle of a bogie. Also, based on the results measured at a track site, the adequacy of vehicle dynamic simulation model was verified. Then the measured results were investigated from the aspects of interacting forces between wheel and rail obtained by vehicle dynamic simulations, and the effect of lubrication on vehicle/track dynamic behaviour was evaluated with the focus placed on the coefficient of kinetic friction and the steering performance of bogie such as lateral force and the angle of attack. This paper describes the detailed arrangements and the results of track site measurements in a sharp curve whose radius was 160 m and vehicle dynamic simulation. As a result, the significant effect of the top of low-rail lubrication on improving vehicle/track dynamic behaviour was identified. Finally the advantage of a kind of friction modifier, called as “friction moderator” in this study, and its jetting device by which the friction moderator was supplied to wheel/rail interface the authors have been developing for the top of low-rail lubrication was discussed.