Rolling contact fatigue, wear and broken rail derailments

Rolling contact fatigue (RCF) and wear are inevitable in the wheel/rail system, but resulting failures and derailments need not also be inevitable. Understanding why and under which conditions broken rails and derailments are likely to occur will focus research, inspection and maintenance efforts to minimize their probability. RCF leads to many broken rails, and rails with severe RCF damage are difficult to inspect. Yet wear reduces the extent of crack growth and hence can be beneficial in some cases. On the other hand, wear changes wheel and rail profiles, may expose virgin material to contact stresses, and reduces the section strength, which may lead to higher stress from bending and torsion. These influences are explored together with case studies of operational derailments. Based on this information and the current state of the art - both theoretical and practical - a number of issues are raised which need to be addressed through further developments in understanding and mitigating strategies to reduce the risk of failures from RCF and wear.