Nonlinear Contact Geometry Effects on Wheelset Dynamics

The nonlinear dynamic behavior of a simply restrained railway vehicle wheelset on tangent track is investigated. Nonlinearities due to the kinematics of wheel/rail contact (excluding flange contact) and creep force variation with creepage are considered for mildly noncircular wheel and rail profiles. The general equations of lateral and yawing motion of the wheelset are derived. These are then simplified by considering both normalized amplitude ε of the motion and angle of wheel/rail contact in the undisturbed position α0 as small parameters. Asymptotic solutions describing the influence of the nonlinearities on the stability and frequency of wheelset motion are obtained using the method of multiple time scales. The results are used to derive conditions for which a linear creep force model is valid.