Experimental Study on Ratcheting Behavior of Different Rail Steels

The rolling contact fatigue failure induced by ratcheting behavior is one of the main modes of rail damage. The investigations of ratcheting behavior evolutions of different rail steels under cyclic loadings are useful for guiding the rail material selection in service. Experimental investigations on cyclic plastic deformation behavior of hot-rolled U71Mn, heat-treated U71Mn, hot-rolled U75V and heat-treated U78CrV rail steels are carried out. The maximum initial plastic strain and peak stress are limited in the same values, respectively, the difference in ratcheting behavior evolutions of different rail steels is discussed. The results show that, for the four materials investigated in experiments, the heat-treated U78CrV and hot-rolled U71Mn rails have the largest and smallest yield strength and ultimate strength, respectively; when the initial ratcheting strain values are similar, the ratcheting strain rates of heat-treated rail steels are larger than that of hot-rolled rail steels, no matter in the initial stage or in the stable stage; when the peak stress is constant, the higher strength rail steel is more resistant to the plastic deformation. The fatigue lives of different steels at a similar failure ratcheting strain are very different, the fatigue lives decrease with the increasing failure ratcheting strain, and the stable ratcheting strain rate can be used for predicting the fatigue crack initiation life at a critical location of different rails. © 2020 Journal of Mechanical Engineering.