中文摘要：

在NENE-2型微动疲劳试验机上对弯-弯条件下PD3、U71Mn钢的疲劳裂纹扩展特性进行了研究。结果表明：相同弯-弯条件下,U71Mn钢中的疲劳裂纹较PD3钢中的短,因而具有较好的抗疲劳性能;其原因在于U71Mn钢的塑性较PD3钢的好,使得裂纹尖端钝化,同时其细小的珠光体具有更多的晶界,从而为能量的耗散提供了更多的途径,最终使得裂纹在U71Mn钢中较在PD3钢中不容易扩展。

英文摘要：

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.