On Discontinuous Dynamics of a Freight Train Suspension System

Abstract

In this paper, a freight train suspension system is presented for all possible types of motion. The suspension system experiences impacts and friction between wedges and bolster. The impacts cause the chatter motions between wedges and bolster, and the friction will cause the stick and nonstick motions between wedges and bolster. Due to the wedge effect, the suspension system may become stuck and not move, which can cause the suspension to lose functions. To discuss such phenomena in the freight train suspension systems, the theory of discontinuous dynamical systems is used, and the motion mechanism of impacting chatter with stick and stuck is discussed. The analytical conditions for the onset and vanishing of stick motions between the wedges and bolster are presented, and the condition for maintaining stick motion was achieved as well. The analytical conditions are developed for the onset and vanishing conditions for stuck motion. An analytical prediction of periodic motions relative to impacting chatter with stick and stuck motions in the train suspension is performed through the mapping dynamics. The corresponding analyses of local stability and bifurcation are carried out, and the grazing and stick conditions are used to determine periodic motions. Numerical simulations illustrate periodic motions of stick and stuck motions. Finally, from field testing data, the effects of wedge angle on the motions of the suspension are presented to find a more desirable suspension response for design.