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Contact fatigue is composed by different damage mechanisms under the action of cyclic loads. From surface microfractures, mainly nucleated because of ratchetting, it is eventually possible to have the formation of ‘pitting’ and ‘spalling’ failures under mode II fracture propagation. The scope of this research is to investigate the propagation of mode II cracks in a rail steel with a ‘four-point bending’ apparatus. The results show that cracks tend to propagate under mode II only for a few hundreds ?m: after this propagation cracks develop either mode I branching or a diffuse mechanical damage at the crack tip.