On the dynamics of European two–axle railway freight wagons

The design of European two–axle freight wagons can be traced back to the 1890’es. It has been and still is widely used in Europe because it is simple, rugged and cheap in price and maintenance. The internationally approved suspension for two–axle freight wagons in Europe is known as the UIC standard suspension (see Fig. 1). Each wagon has four of these suspensions. They consist of a leaf spring and UIC links. The leaf spring rests on the axle box and provides the vertical suspension. Dissipative dry friction forces are generated for an operating leaf spring because the leafs will slide against each other. The car body is connected with the leaf spring through the UIC links that works as a pendular suspension with friction. This yields the necessary stiffness and damping for the horizontal motion. The only damping mechanism in the UIC suspension is dry friction. The axle guidance (see Fig. 1) works as motion delimiters. It simply restricts the relative motion between the wheelset and the car body by an end stop, if the translation or yaw motion of the wheelset becomes sufficiently large. This paper deals with the modelling and analysis of the dynamics of two–axle freight wagons. Central to this is the mathematical modelling of the nonsmooth interacting forces determining the motion of the vehicle. The model is used to examine the dynamics of two–axle freight wagons in order to clarify and understand the poor running properties that many freight wagons exhibit at moderate speeds.