Assessment of the curving performance of heavy hau

Authors: Liangliang Yang Yu Kang Shihui Luo Maohai Fu

Publish Date: 2015/05/27

Volume: 23, Issue: 3, Pages: 169-175

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Abstract

To study the curving performance of trains 1D and 3D dynamic models of trains were built using numerical methods The 1D 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 1D model under braking conditions the behavior of draft gears and brake shoes were added to the 3D 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 wheelrail 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 difficultWith the rapid development of heavy haul railways an increase in wagon number of heavy haul trains has been an important way to improve transportation capacity However the longer a train is the more time it generally takes to decelerate or stop Thus greater longitudinal impulses may occur between adjacent wagons Based on extensive theoretical and experimental research problems such as damage to the vehicle structure and train derailments were found to be caused by the longitudinal impulses from train braking To solve these problems many scholars included train braking conditions when assessing train performance especially the curving performance of trains Durali and Ahadmehri 1 studied the derailment coefficient of a fivecar train under emergency braking conditions modeling with complete degrees of freedom DOFs but the calculations involved excessive computational costs Zhang et al 2 3 4 discussed safety and comfort indexes under idling traction and braking conditions for a long and heavy haul train His circular variable method was acknowledged as a lowcost approach to simulating train system dynamics Pugi et al 5 focused on the relationship between coupler force and relative load reduction His work was performed using multibody dynamics and pneumatics methods Ma et al 6 Wu et al 7 and Xu et al 8 showed that the wheelset lateral force would vary with coupler compression and rotation when the electric brake was operated on a tangent or curved track Cole et al 9 demonstrated that wheel load reduction occurred during train braking in which nodding movement between the rail car body and bogie was taken into account Sun et al 10 and Liu and Wei 11 reported that derailment indexes change with the coupler deflection angle when a train of 10000 tons proceeded around a curve with air brake operationIn these previous research efforts attention was paid to the relationship between draft gear behavior and wheelrail interaction but the effect from the brake shoe pushing the wheel tread was usually of less concern In this study dynamic models of 1D and 3D trains were established using numerical methods in which the dynamic behaviors of draft gears and brake shoes were both considered The assessment of the curving performance of trains focused more on making comparisons between idling and braking conditions Furthermore this study provides a feasible approach to solving the rapidly increasing freedoms considered in train system dynamicsThe train under consideration was equipped with 2 HXD2 locomotives and 210 C80 wagons Used on the Datong–Qinhuangdao line the electric locomotive and the coal gondola were both heavy haul freight cars with 25 t axle loading In the 1D train model all cars were simplified as a series of mass points that allowed only longitudinal motion Also each car was subject to a coupler force from the draft gear a basic propulsion force and an air brake force These forces whether from the locomotive or wagon can be described by different equations Moreover only traction and dynamic brake forces were added to each locomotiveAccording to the simplification above the 1D train dynamic model was established using MATLAB/SIMULINK software 13 It was only able to solve longitudinal dynamic problems However no matter which car of the train is under consideration the coupler force and brake shoe pressure that varied with braking time can easily be obtained

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