Abstract:This article describes an investigation on the relative motion between wheel-set and rails. Through the search of an equilibrium configuration, the positions of contact points between rails and wheels are first located. The detection methods allow also the definition of the normal unit vectors to rail and wheel at contact points. To reduce computing time, the results are stored in a lookup table accessed during the dynamic analyses of wheel-sets, bogies, or trains. The use of lookup table considerably speeds up contact detection when numerically integrating with respect to time.

The present paper analyzes the dynamics of a bogie composed of two wheelsets and a frame. The bogie frame is joined to the wheelsets by means of a primary suspension system, acting on the three principal directions, i.e., longitudinal, transverse and vertical.The bogie moves along rails following its variable path. In particular, the dynamic analysis investigates the bogie behavior in both straight and curved paths, with or without an initial perturbation. Imposing an initial disturbance, the hunting motion is observed and the critical speed value estimated.The present analysis uses a lookup table for the determination of the contact characteristics. In order to minimize cpu-time, a new procedure for the interpolation of the lookup table entries has been developed. Finally, two different methods for the integration of the differential equations have been tested and comparisons with the results obtained by commercial multibody software are discussed.