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Wheel-Rail Corrugation

Contact : Christophe Collette

Motivation

Rail corrugation is a way wear of the rail surface. Different types of rail corrugation have been identified and classified (Fig. 1) involving different resonances of the coupled vehicle-track system. Even if the phenomenon is as old as the rail, its modelling and mitigation remain a challenging task.

Fig. 1: Classification of the different types of rail corrugation.

Modelling

During the last 20 years, different approaches for the study of rail corrugation have been developed; these can be classified in two categories: frequency domain corrugation theories and time domain non-linear models (Fig. 2). Although numerous publications examine these techniques the literature, few comparisons have been published. The motivation of this work is to compare these approaches on test cases in order to test their accuracy and limits of validity.

Fig. 2: General procedure for the evaluation of corrugation growth rate in the time and frequency domain.

Solutions

Rail corrugation of type 2 (Fig. 1) involves two resonances of the vehicle-track system: the unsprung masses resonance or a sleeper resonance in the vertical direction and a torsional resonance of the wheel set in the longitudinal direction. Once the rails have been damaged, grinding is the only way of removing existing rutting corrugation from the rail surface, but it does not prevent the phenomenon of reappearing after a while.

So far, effective measures to prevent rutting corrugation are of four types: (i) decrease the vertical force (i.e. use vertically soft rail pad to decrease the vertical resonances); (ii) use harder rail steel; (iii) decrease the longitudinal creep force (improve the steering of the vehicle in curve using resilient yaw suspension or steering bogie, less severe curves on freight track); (iv) modify the friction coefficient with lubricant or friction modifier. Solutions of the first three types are acting on the causes of the phenomenon, but need some modifications of the existing vehicle-track system. Solutions of the fourth type have proved their efficiency but have other drawbacks. The solution developed in this work is based on the use of a DVA to reduce the vibration amplitude of the torsional mode of the wheel set (Fig. 3). The efficiency of the DVA is evaluated theoretically (Figure 2), and experimentally (Fig. 4) on a scaled test bench (INREST – Laboratoire des Technologies Nouvelles).

Fig. 3: DVA mounted on the wheel set axle: (a) tuned on the first torsional resonance; (b) tuned on the second torsional resonance.

Fig. 4: Picture of the experimental set-up (INRETS – Laboratoire des Technologies Nouvelles).