Comparisons Between Braking Experiments and Longitudinal Train DynamicsUsing Friction Coefficient and Braking Pressure Modeling in a Freight Train

Background:This paper describes the predictions and validation of the pneumatic emergency braking performance of a freight train consisting of a locomotiveand 20 wagons, generally operated in Korea. It suggests the possibility of replacing the expensive and time-consuming train running tests withlongitudinal train dynamic simulations. Methods:The simulation of longitudinal train dynamics of a freight train uses the time integration method of EN 14531. For reasonable simulation results,the characteristics of the train and brake equipment must be considered. For the train characteristics, specifications provided by the vehiclemanufacturer are used. The braking characteristics are analyzed by friction coefficient tests and a braking pressure model. The friction coefficientsof a locomotive and wagons are tested with a dynamo test bench and statistically expanded to account for variability. Freight trains should take intoaccount the braking delay time. To reflect this in the simulation, the brake cylinder pressure pattern model uses pressures and exponential empiricalequations measured at selective positions in a train of 50 vehicles. The simulation results are validated in comparison with those of the brakingtests of a freight train consisting of 1 locomotive and 20 wagons. Results:The results of the longitudinal dynamics simulation show very similar results to the running test results based on the speed profile and brakingdistance. Conclusion:In particular, the statistical expansion method of the friction coefficient enables robust prediction of the distribution of the braking distance. Thesimulation can reduce or make up for costly and time-consuming repeated braking tests and reduce the risks that may arise during testing