4.5Ni钢表面裂纹的低周疲劳扩展行为研究

Propagation Behavior of Low-cycle Fatigue Surface Crack in 4.5Ni Steel

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。

The propagation behavior of low-cycle fatigue surface cracks in 4.5Ni steel was analysed with cantilever-bending loading and total strain range as an examined and controlled parameter. The relationship between crack growth rate d(2 a )/d N and total strain range Δε T was given. The examination of microscopic appearance of low cycle fatigue fracture was conducted. The results show that for the low-cycle fatigue cracking propagation of 4.5Ni steel a transcrystalline mode is predominant with a crystallogic ductile fatigue striation and the fatigue crack propagation is of plastic passivation model mechanism.