A new wear model considering wheel-rail conformal contact

One of the fundamental issue in railway field is the wheel and rail wear due to the wheel-rail contact, which directly impacts both on vehicle dynamic behaviour (comfort, stability, etc..) and on economical aspect (maintenance). Hence, the aim of this work is the development of a new wear model for the evaluation of the wheel and rail profile evolution based on an innovative wheel-rail conformal contact model. Conformal contact conditions are really frequent in railway applications, particularly in sharp curves and, generally, in presence of worn profiles. Because all this reason, if an accurate wear assessment is required, this aspect cannot be neglected. In the proposed wear model, two separate units mutually interact: a vehicle model for the dynamical analysis and a model for the wear evaluation. In the first one a 3D multibody model of the vehicle and an innovative 3D conformal contact model based on an improvement of the Piotrowski theory interact online during the dynamic simulations. Starting from the outputs of the dynamic simulations (position and shape of the contact patches, contact pressures, etc.), the wear model calculates the specific volume of removed material by wear through suitable experimental laws that correlate this volume to the friction power produced by the tangential contact pressures. Finally, the new updated profiles of wheel and rail are obtained by subtracting the material removed from the old ones. The research activity has been carried out in collaboration with Hitachi Rail Italy, which provided all the technical and experimental data needed for the preliminary model validation.