Rolling contact fatigue study of railway rails

This work analyses the wheel-rail interaction in terms of rolling contact fatigue (RCF). For this purpose, a full scale testing machine was designed and built in order to apply the loads and boundary conditions appearing in the railway (up to 30 tons per wheel, application of lateral load in bends, inclination, angle of attack, presence of dust, water…) Eight tests were performed under different load conditions and rail grades and RCF cracks were generated after 50000 to 100000 cycles. The occurrence of cracks was determined by magnetic particle inspection at regular intervals in the course of the tests. When the non-destructive inspection showed the existence of cracks, the test was stopped and the rail longitudinally and transversally cut to perform a metallographic analysis in order to know the nature, growth direction, shape and size of the cracks. The cracks generated in the laboratory tests were identical to those seen in RCF affected railways and significant variations were found in the behavior of the different rail grades. The proposed test was able to simulate the damage produced in rails by RCF and allows the comparison of the fatigue behavior of different rail grades under highly controlled conditions

Study on the wear and rolling contact fatigue behavior of rail steel grades using a twin disc laboratory equipment

The wear resistance and the rolling contact fatigue (RCF) behaviour of different rail steel grades versus a railway wheel steel is analysed in this work. For this purpose, a twin-disc test was setup, in order to replicate the in-service damage suffered by the rails due to the contact pressure appearing in the rail and to analyse the wear and RCF behaviour of the rail steel in a quick and efficient way. Different rail steel grades have been studied under different test conditions and the influence of the applied load and the sliding rate on the wear and RCF behaviour of these materials has been analysed. At the end of the tests, the specimen mass loss was determined and degradation phenomena assessed by metallographic characterization. The nature, shape and size of the cracks were analysed and compared to those obtained in the tests carried out with the same materials at a pilot plant scale. It has been demonstrated that the proposed Twin-Disc tests are able to predict the behaviour of the different steel grades in rail-wheel systems in a quick and easy way.The authors acknowledge the Ministerio de Economía y Competitividad for financing IPT-2012-0320-420000 project, in whose context this work was performed