Laser measurement of torsional vibrations/longitudinal creepage of a railway wheel set on a scaled test bench

Since more than one century, test benches remain an essential tool to study various aspects of the railway dynamics such as for instance running stability, safety or even ride comfort. For each of these applications, the knowledge of the contact conditions (forces and relative displacements) between the wheel and the rail is a necessary condition to develop a sound understanding of the physical phenomena. More specifically, as soon as the longitudinal dynamics of the vehicle-track system is involved in the study (like for the performance of a locomotive, the rolling noise or rail corrugation), a precise measure of the longitudinal creepage between the wheel and the rail is needed to verify numerical predictions from theoretical models. In this paper, we focus on the measurement of torsional vibrations of a scaled wheel set which is rolling on a roller (representing infinite rails). First, a theoretical overview of the conditions under which these torsional vibrations are excited is given. Then, the experimental set-up used to study the phenomenon is presented. During the experiment, the wheel set torsional vibrations are measured using the rotational laser Doppler vibrometer, and the measure is used to calculate the longitudinal creepage of the wheel. Results are compared with outputs of a multi-body model of the test bench.