Effects of the change in auto coupler parameters on in-train longitudinal forces during brake application

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.