Abstract
For long freight trains, the pneumatic brake systems are still used. In these situations, the cars at the end of the train brake a few seconds later than those wagons at the front. This variable braking action along the train may cause large longitudinal forces and impacts. Beside brake system parameters, auto coupler characteristics parameters have high importance in longitudinal train dynamics. Therefore, simulations of effects of the change in auto coupler parameters on in-train longitudinal forces during brake application are very important both for safety and economic reasons since longer freight trains imply higher transport costs reductions. In the present paper, effects of the change in coupling parameters such as stiffness, damping, and clearance and train speed, on the longitudinal train dynamics were investigated during brake application. The results indicate dramatic changes in the way that cars interact dynamically with each other and the magnitudes of the in-train longitudinal compression and tensile forces along the train. The freight train considered is in current use by Iranian Railways.
Highlights
Dynamic brake is another kind of brake system, which might be applied in locomotives
The model of wagon connection can be simplified to a combined draft gear package model equivalent to two draft gear units and one spring element representing locked stiffness, the locked stiffness is the sum of all the stiffness of elements such as the coupler shank, knuckle, yoke, locked draft gear and wagon body all added in series
Simulations are conducted for three different cases based on change in coupling stiffness, coupling clearance, and damping parameters, which are characteristic of auto coupler
Summary
In 1993, El-Siabie reported that lateral and vertical components of forces resulting from coupler angles on horizontal and vertical curves are quite large [5] These components will adversely affect wagon stability with the possibility of train derailment at some points. Verbitskiy et al reported similar results for a monorail car in 2000 [9] They looked at the relationship between lateral in-train coupler force components and wheel unloading. Effects of different operating parameters (such as stiffness and damping of automatic couplers, train forward speed, coupler clearance, and train acceleration and braking processes) on longitudinal train dynamics were investigated parametrically. An extensive parametric study is carried out to find out how changes in the design and operational parameters Such as changes in stiffness, damping, and clearance and train speed affect the longitudinal train dynamics. All the input parameters are in full accordance with those currently used in Iranian railways
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