通过COD位移规控制悬臂弯曲加载试样表面裂纹前缘的应变，采用逐级递增应变的试验方法，研究了10CrNiMo结构钢的低周疲劳表面裂纹的扩展特性，并用扫描电镜对断口形貌进行了观察。结果表明：表面裂纹扩展速率与裂纹前缘总应变范围之间满足良好的幂律关系；裂纹源附近出现轮胎花样，裂纹扩展初期挤压严重，扩展中期发现较多的二次裂纹，扩展后期疲劳辉纹清晰可见，最后断裂区具有典型的韧窝；裂纹按照锐化-钝化机制扩展，最后断裂模式为韧性断裂。
The strain of surface crack front of cantilever bend loaded sample was controlled by COD displacement gage, the propagation characteristics of low cycle fatigue surface crack of 10CrNiMo structural steel were studied by increasing the strain gradually, and the fracture morphology was observed by scanning electron microscopy. The results show that the surface crack propagation rate had good power ruler relation with the total strain range for crack front. Some tyre-figure appeared near the crack source, serious squeezing happened at the beginning stage of crack propagation, major secondary cracks were found at the middle stage of crack propagation, the fatigue striation was obvious at the late stage of crack propagation, and typical dimples were found on the last fracture area. The crack propagated in sharpening-blunting mechanism and fractured in toughness mode finally.
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