Keywords: contact, tribology, creepages, scaled test-bench, twin-disc, wear.

The sliding velocity of a wheel travelling through a rail is the main responsible for wear. This phenomenon changes wheel and rail profiles influencing vehicle dynamics. For this reason, an optimized grinding schedule, which gets back the original profiles, plays a crucial role to ensure an economically reasonable rail life cycle while assuring running safety. Predictive methodologies for wear damage help to plan the maintenance schedule. These methodologies are based on known wear rates. As an on-site characterization of wear mechanism is difficult, test rigs are widely used. Twin-disc machines and scaled test-benches are the most common. A comparative study of the contact patch is presented under the equivalent conditions that are given in the wheel-rail interaction. For that purpose, the normal and tangential problems are solved for elliptical and rectangular contacts with their pertinent formulation. The contact conditions of a twin-disc machine differ with respect to real wheel-rail contact, in area shape and slip area ratio. This not occurs on the scaled bench, where the shape of the contact area and the slip area ratio remains identical. As the slip between different surfaces is the main responsible of wear damage, these observed contact differences regarding the slipping area, disrupt the wear rates when are directly applied from twin-disc machines.

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