Coupling between structural deformations and wheel—rail contact geometry in railroad vehicle dynamics

Abstract

This investigation aims to demonstrate the effect of structural flexibility on the wheel—rail contact location and forces in railroad vehicle dynamics. It is shown that there is a strong dynamic coupling between the car body deformation coordinates and the wheel—rail contact parameters and geometry that depend on the wheel and rail surface profiles. In particular, two wheel profiles are considered in this study in order to examine the coupling between the geometry and structural flexibility. The first profile allows for a second point of contact on the flange of the wheel, while the second profile is designed such that the wheel cannot have more than one point of contact with the rail. The coupling between the deformation of the car body and the contact geometry is demonstrated through the comparison of computer simulations of a railroad tank car modelled with a flexible tank and a rigid tank. The simulations are performed using the methods of multi-body dynamics utilizing a fully non-linear multi-body framework and an elastic three-dimensional wheel—rail contact methodology. Structural flexibility is incorporated into the equations of motion by means of the floating frame of reference formulation, allowing for a small deformation, linear finite-element mesh to undergo arbitrarily large reference displacement and rotation. The resulting coupled, non-linear differential-algebraic equations are solved using well-known methods of numerical time integration.