Influence of Wheel/Rail Contact Geometry on Large Amplitude Wheelset Equations of Motion

The nonlinear equations of motion and velocities of creep of a simply restrained wheelset on tangent track are derived for the case of large amplitude motion including flange contact. The nonlinearities considered are those arising from the wheel/rail contact geometry. It is shown that during flange contact the lateral creep velocity may differ by as much as 30-40 percent when compared to that calculated using the usual creep velocity models. Furthermore, the use of the equations of rolling and vertical motion as a means of defining the wheel/rail normal constraint forces results in the inclusion in the dynamic model of several effects not usually included. The equations of motion which result for the lateral translation and yaw of the wheelset contain substantially different loadings than those used in most models. The attendant effect on wheelset stability may be significant.