Assessment of the curving performance of heavy haul trains under braking conditions

摘要

To study the curving performance of trains,ID and 3D dynamic models of trains were built using numerical methods.The ID model was composed of 210 simple wagons,each allowed only longitudinal motion;whereas the 3D model included three complicated wagons for which longitudinal,lateral,and vertical degrees of freedom were considered.Combined with the calculated results from the ID model under braking conditions,the behavior of draft gears and brake shoes were added to the3 D model.The assessment of the curving performance of trains was focused on making comparisons between idling and braking conditions.The results indicated the following:when a train brakes on a curved track,the wheel-rail lateral force and derailment factor are greater than under idling conditions.Because the yawing movement of the wheelset is limited by brake shoes,the zone of wheel contact along the wheel tread is wider than under idling conditions.Furthermore,as the curvature becomes tighter,the traction ratio shows a nonlinear increasing trend,whether under idling or braking conditions.By increasing the brake shoe pressure,train steering becomes more difficult.