Wear modelling in rail-wheel contact

In rail-wheel transports the maintenance interval for both wheels and rails has become a major issue in reducing costs and increasing safety and has encouraged the development of new numeric procedures for predicting the evolution of wear in order to establish a convenient maintenance schedule. These new tools require the synergy of dynamic analysis and the development of accurate and easy to use wear models. Rail/wheel wear depends on the material properties resulting from contact fatigue and sliding wear. Therefore, all the contact conditions affecting the contact stress distribution will determine the wear behaviour and the contact profiles of wheel and rails. The current research paper investigates the effect of contact conditions on friction and wear behaviour of EN 260 rail steel and R7 wheel steel. Laboratory simulation used twin-disc rolling-sliding tests to study the effect of the creep ratio, contact pressure and tangential speed on the resulting traction coefficient and amount of wear. The volume loss was estimated by weighing both specimens before and after the tests. Wear volumes were used to develop a wear equation based on Archard׳s model and considering weighting factors to estimate the influence of creep ratio, contact pressure and tangential speed on the specific wear rate. The predicted results were compared with the results of tests performed in the laboratory. Quite small differences between previsions and laboratory tests confirm the reliability of the forecast method. Wear mechanisms were discussed and compared to real rail-wheels sets analysing the fatigue cracks and the strain hardening effects beneath the contact surfaces.