IDENTIFICATION OF WHEEL/RAIL CREEP COEFFICIENTS FROM STEADY STATE AND DYNAMIC WHEELSET EXPERIMENTS

The dynamic response and curving performance of railroad vehicles are strongly influenced by contact forces generated at the wheel/rail interface. These forces, known as creep forces, result from differential translational and rotational velocities, known as creepage, between the wheel and rail surfaces. Under controlled conditions these forces may be predicted analytically using the theory of Kalker (1), but under actual running conditions creep forces may vary considerably from the ideal. It is desirable, therefore, to be able to measure creep forces under typical operating conditions, so that realistic values for their magnitudes may be included in analyses of vehicle performance. This paper presents several techniques for measurement of creep forces on running wheelsets under steady state and dynamic conditions, and discusses practical considerations in achieving accurate results. Maximum likelihood parameter identification is demonstrated as a useful technique for extracting creep coefficient data from measurements of wheelset dynamic response to track alignment and rolling line offset inputs.