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采用悬臂弯曲加载方式，以总应变范围作为受检和控制参数，分析了高强度４．５Ｎｉ钢表面裂纹的低周疲劳扩展行为，给出了裂纹扩展速率ｄ（２ａ）／ｄＮ与总应变范围ΔεＴ的关系式及关系曲线。同时对弯曲加载条件下低周疲劳损伤断口微观形貌进行了观察分析。指出４．５Ｎｉ钢的低周疲劳裂纹扩展方式主要是穿晶，疲劳辉纹为晶体学延性辉纹，疲劳裂纹扩展属于塑性钝化模型机制。
Using the cantilever bending loading method and the total strain range as the inspection and control parameters, the low-cycle fatigue propagation behavior of high-strength 4.5Ni steel was analyzed. The relationship between the crack growth rate d (2a) / dN and the total strain range ΔεT of the relationship and the relationship curve. At the same time, the microstructures of low-cycle fatigue damage fracture under bending loading were observed and analyzed. It is pointed out that the low-cycle fatigue crack growth mode of 4.5Ni steel is mainly transgranular, the fatigue glitch is the crystallographic ductile fringe, and the fatigue crack growth belongs to the plastic passivation model mechanism.