| In recent years,the subway has played an increasingly important role in urban transportation.However,with the increase of passenger traffic and the increase of operating speed,the phenomenon of wheel/rail wear has become more and more serious.Traditional wheel-rail lubrication is one of the effective measures to reduce the side wear of curved rails and extend the service life of wheel-rails.In order to ensure a high adhesion coefficient between the rail top and the wheel tread,traditional lubricants can only act on the rail gauge or the wheel flange.Wheel-rail friction control refers to a technology that adjusts the friction coefficient of the wheel-rail interface by applying friction modifiers to keep the wheel-rail friction characteristics in a better state under the condition of meeting the adhesion coefficient required for the normal traction and braking of the train.Previous studies on wheel-rail friction control mainly focused on standard profile rails.However,the most commonly used scene for wheel-rail friction control in subway lines is on small and medium-radius curves,and rail wear in small and medium-radius curves is usually more obvious.Therefore,it is necessary to conduct wheel-rail friction control research on worn rails.This thesis conducted a field survey on a domestic subway line and measured the rail profiles after wear with different characteristic curves.Then,the subway vehicles running on the curved lines with the standard and after wear rail profiles were used as the research object,combined with the vehicle system.Dynamics and friction work theory.By comparing the effect of friction modifiers on standard rails and wear rails,the simulation studies the effects of friction modifiers on vehicle safety,stability and wheel-rail wear characteristics under different friction control strategies.And studied the influence of other operating conditions on the effect of friction modifier.The main research work and conclusions of the thesis are as follows:1.Use SIMPACK to establish a subway vehicle system dynamics model that can consider different wheel-rail friction control strategies,and then use this model to simulate and study the effect of wheel-rail friction modifiers;An on-site survey was conducted on a domestic subway line.The rail profiles after wear with different characteristic curves provide a basis for comparing the effects of friction modifiers on standard rails and worn rails.2.The effect of symmetrical friction control on the rail top is studied.The research results show that: Compared with no friction control of the rail top,whether the rail side is lubricated or not,the friction modifier applied to the rail tops on both sides can effectively reduce the derailment coefficient and wheel-rail lateral direction.Indexes such as force and lateral stability of the car body,and the effect on the worn rail is better than that of the standard rail;The friction modifier reduces the guiding torque,resulting in an increase in the wheelset yaw angle;The friction modifier on the tops of the rails on both sides can be significantly reduced the wear index of the rails on both sides,in which the curved outer rail makes the wheel flange abutting phenomenon more serious after wear,and has a tendency to aggravate the wear.Therefore,the wear rail needs more friction control than the standard rail.3.The effect of asymmetrical friction control on the rail top is studied.The research results show that: Compared with the no friction control of the rail top,the friction control of the inner rail and the top of the rail can significantly reduce the safety index when the vehicle passes the curve.In contrast,the effect of the outer rail top friction control is not obvious;Compared with rail top symmetrical friction control,the rail top asymmetric friction control mode has a higher car body stability index;In reducing the wheel-rail wear index,the effect of inner rail top friction control is better than the friction control on the top of the outer rail,however,it is weaker than the friction control on the top of the rail on both sides.4.Discuss the influence of other operating conditions on the effect of friction modifiers.The results of the study show that the effect of friction modifiers on the derailment coefficient,wheel yaw angle,wear index and other indicators under the conditions of under-superelevation is relatively high.The effect of friction modifier on the driving safety and stability of the vehicle is similar when the vehicle passes through the curve under different track slope conditions;When the track slope is large,the effect of friction modifier on the driving safety and stability of the vehicle is similar.The friction modifier has a more obvious reduction effect on the rail wear index. |
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