Abstract

A comprehensive finite element (FE) model of railway vehicle-track system is developed to study the dynamic interaction between the vehicle and track. The vehicle is represented by a lumped parameter system. The track is modeled as a Timoshenko beam on discrete pad-tie-ballast supports. The tie is considered either as a rigid body or a non-uniform beam. The rail-pad and ballast are modeled as distributed spring-damper elements. The non-linear factors such as loss of wheel/rail contact, rail lift-off from the tie and tie lift-off from the ballast are taken into account. A cutting and merging method along with a set of special boundary conditions is established to extend finite length of track to infinitely long track so that a vehicle can be modeled to travel on the track indefinitely with a time-dependent speed. A numerical direct integration technique is employed to solve the equations of motions of the vehicle and track systems. An adaptive multi-point wheel/rail contact model is proposed and used to calculate the normal and geometrical longitudinal forces due to irregularities in the wheel/rail contact region. The developed FE model is validated using the experimental data obtained from British Rail and Canadian Pacific (CP) Rail. The FE results such as natural frequencies of concrete ties, the wheel/rail contact forces, the rail-pad forces and dynamic strains in the rail, generally show good correlation to the experimental data. The validated model is applied to investigate the characteristics of impact loads due to wheel/rail tread defects such as wheel flats, wheel shells and rail joints. The steady-state interaction between the vehicle and track, and the dynamic force due to rail corrugations are evaluated for high speed operation. The results of this study show that the impact load is maximum at the ties, and is strongly influenced by the axle load, vehicle speed, actual shape of the defect, and rail equivalent mass. Elastomeric shear pads on the wheelset bearing, and reduced rail-pad stiffness, can potentially reduce dynamic bearing force and tie dynamic load, respectively. The magnitude of resonant force for vehicle-track system in a steady-state interaction mainly depends on the unsprung mass, tie spacing, vehicle primary and track ballast damping, and rail stiffness. In the presence of rail corrugation, the energy consumption due to longitudinal force increases quadratically with the depth of rail corrugation. The dynamic contact forces at neighboring wheels are influenced by each other and the basic mechanism that control such an interaction is the superposition of the dynamic responses. Stable solution in the speed range 0 to 1440 km/h demonstrates the effectiveness of the model for high speed simulation.