Investigation of the influence of rail pad stiffness on rail corrugation on a transit system

This paper presents a study on the influence of rail pad stiffness on rail corrugation in an underground line. The paper includes a theoretical analysis justifying the rationale behind the modification of the pad stiffness to reduce corrugation levels, as well as a set of corrugation measurement results took on a test curve section during a period 19 months. The aim of the work is to demonstrate clearly that this treatment, studied by other authors like Ilias [H. Ilias, The influence of railpad stiffness on wheelset/track interaction and corrugation growth, J. Sound Vib. 227 (1999) 935-948], works on a metro system. In this study, the conventional rail pads on a test curve were substituted by softer pads. In order to examine the influence of new rail pads on corrugation, the rail profile was measured before and after the track modifications, during the same period of time. For both situations, wavelengths and amplitudes were analyzed and compared. It was found that soft pads reduce corrugation growth and eliminate one of the wavelengths developed when using stiff pads. The theoretical results were obtained from a model developed by Tassilly and Vincent [E. Tassilly, N. Vincent, Rail corrugations: analytical model and field tests, Wear 144 (1991), 153-161; E. Tassilly, N. Vincent, A linear model for corrugation of rails, J. Sound Vib. 150 (1991) 25-45]. This linear model for the corrugation of rails was used to predict the frequency bands in which corrugations are likely to appear. The track and the wheelset dynamics were studied both experimentally and theoretically. Quasi-static wheel/rail forces and creepages have been obtained with a multibody model of a metro unit. The methodology followed to compare the theoretical and experimental results is based on the work carried out by Grassie and Elkins [S.L. Grassie, J.A. Elkins, Rail corrugation on north american transit systems, Vehicle System Dyn. 28 (1998) 5-17]. The correlation between simulated and experimentally measured corrugation wavelengths appearing in the inner rails of curves is analyzed, and the corrugation mechanism is explained.