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通过对带有环状Ｖ型切口的４５￣＃钢圆棒料在恒幅过载和变幅过载下的低周次疲劳试验，表明变幅递增过载的裂纹扩展速率比恒幅过载裂纹扩展速率显著增大。基于试验事实和断口分析，探讨了过载下的疲劳裂纹扩展机制，说明过载时裂纹扩展速率瞬时显著增大是裂纹钝化的结果，进而寻找到了促使裂纹加速扩展的适宜加载方式，为超低周疲劳断裂的工程应用提供了依据。
The tests of low cycle fatigue of 45 ~ # steel round bars with annular V-shaped cutouts under constant amplitude overload and amplitude overload show that the crack growth rate under increasing amplitude overload is significantly higher than that under constant amplitude overload crack propagation rate Increase. Based on the experimental facts and the fracture analysis, the mechanism of fatigue crack propagation under overload is discussed. It is shown that the crack propagation rate is significantly increased when the load is overloaded. It is the result of crack passivation. Then the suitable loading method to accelerate the crack propagation is found. Fatigue fracture engineering provides the basis.