DYNAMIC ANALYSIS OF TRACK-WHEEL INTERACTIONS FOR HIGH-SPEED TRAINS THROUGH BOND GRAPHS

Abstract

Over the past few decades, railway industries worldwide have been dedicated to enhancing train speeds and load-carrying capacity. However, as train speeds increase, concerns about wheel-track interaction, safety, and passenger comfort have become paramount. The rise in speed and load capacity leads to heightened vibrations in the vehicle-track system, caused by irregularities on the wheel/rail surface. In light of these challenges, the present study aims to shed light on various aspects of railway dynamics concerning safety and comfort, employing the bond graph methodology. The interaction between the vehicle and the track is a critical factor influencing the safety and comfort of passengers. To investigate this interaction, a comprehensive bond graph model of an asymmetrical railway vehicle-track system is developed. In this model, the vehicle is represented as a lumped system, while the rail and concrete slab are treated as an Euler Bernoulli beam. To delve deeper into the dynamics, the study involves the development of a 1 Degree of Freedom (DOF) wheel model and a 9 DOF half-car vehicle model using the bond graph approach. These models help examine the impact of wheel flat on vehicle track dynamics. Furthermore, the effects of slab track and ballasted track on vehicle dynamics are also discussed. The study also focuses on investigating the hunting behaviour of a railway vehicle using a 31 DOF full railway vehicle model as it moves on a curved track. By utilizing the Heuristic nonlinear creep model and Polach theory, the critical hunting speed is determined, and the responses of vehicle components above, at, and below the critical velocity are presented. The authors also examined the derailment behaviour, wheel unloading rate, wheelset lateral forces, and car body acceleration of the developed model due to alignment and cross-level track irregularities. vii To assess passenger comfort for high-speed trains, the mean comfort assessment method is utilized. This involves the development of a 50 DOF full-car body model in SIMPACK. The effect of random track irregularities on the passenger ride index with varying vehicle speeds is studied. Also, the study observes the effect of vehicle motion on the passenger ride index. In conclusion, the study utilizes bond graph methodology to address various aspects of railway dynamics concerning safety and passenger comfort. The comprehensive models developed provide valuable insights into the interactions between the vehicle and track, helping to enhance railway safety and passenger comfort in high-speed trains.