Modelling a Flexible Track in Multibody Railroad Dynamic Simulations

In this investigation a new formulation that can be used to model the track flexibility in railroad dynamic simulations is presented. In contrast to the regular frame of reference formulation used in flexible multibody dynamics, the proposed formulation introduces shape functions for the description of deformation which are defined in a trajectory frame of reference instead of in the body frame of reference. This trajectory frame of reference moves along the track with the same speed as the vehicle does. The selected moving shape functions are those that show a beam on Winkler foundation when a moving load is applied on it. The fact that these functions are not fixed with respect to the body frame introduces new terms for the description of the inertia forces that appear in the track. Results are obtained for an unsuspended wheelset moving on a tangent track for different stiffness foundation. Results are also compared with those obtained on a rigid track.