Bend-Bend Fatigue Crack Propagation Characteristics of PD3 and U71Mn Rail Steels

The fatigue crack propagation characteristics of PD3 and U71Mn rail steels under bend-bend condition were investigated using NENE-2 fretting fatigue test machine.The results indicate that under the same bend-bend condition the fatigue crack was shorter in U71Mn steel than in PD3 steel,so the former had better fatigue resistance than the latter.One reason was that the excellent plasticity of U71Mn made crack tip passivated.An other rcason was that the refined pearlite with more grain boundaries provided more ways to dissipate energy.Because of above reasons,crack propagation in U71Mn rail steel was more difficult than in PD3 rail steel.