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作者从粗糙度诱发裂纹闭合的几何模型着手,通过推导得出了应力比、显微组织与裂纹闭合间的关系表达式,并就U71Mn钢不同奥氏体晶粒、不同应力比对裂纹闭合以及门槛值附近疲劳裂纹扩展行为的影响进行了研究。结果表明,粗大奥氏体晶粒由于有较大的断面粗糙度,使裂纹闭合程度增大,从而提高门槛值,但它不影响中速区域疲劳裂纹的扩展。应力比除了影响裂纹扩展的微观过程外,主要是影响裂纹闭合。随着应力比的增加,裂纹闭合作用减少,表现出裂纹扩展速率的提高和门槛值的降低。
The author starts with the geometric model of roughness-induced crack closure, and derives the expression of the relationship between stress ratio, microstructure and crack closure by deducing the relationship between crack closure and different austenite grains in U71Mn steel The effect of fatigue crack growth behavior near the threshold is studied. The results show that the coarse austenite grains increase the threshold due to the larger cross-sectional roughness and increase the degree of crack closure, but it does not affect the expansion of fatigue cracks in the medium-speed region. Stress ratio in addition to affecting the microcracks of crack growth process, the main impact of crack closure. As the stress ratio increases, the crack closing action decreases, showing an increase in crack propagation rate and a decrease in the threshold value.