Cyclic plastic strain based damage tolerance for railway axles in China

Railway axle is one of the most important safety critical components usually operated over a service life of 30 years or more in the order of 109 cyclic loading. Therefore, any derailment caused by fatigue damage should be rigorously inspected, assessed and repaired in both routine and emergence maintenance. By considering the effects of crack closure and load ratio, based on plastic strain energy and modified Rice-Kujawski-Ellyin solution in the tip of a growing fatigue crack under plane stress condition, a new crack closure based fatigue crack growth rate model entitled LowGRO has been proposed in terms of low cycle fatigue behavior and improved threshold stress intensity factor range at different loading ratios. For the railway axle used steel 25CrMo4, 34CrNiMo6 and open-reported structural materials, predicted results of current LowGRO are in good agreement with the experimental data. The LowGRO provides a potential compliment during the damage tolerance design like standard NASGRO equation commonly used for high-speed railway axles.