本文综合了文献中关于门槛值及其附近疲劳裂纹扩展规律等方面研究的近期成果,对影响低应力下疲劳裂纹扩张和门槛值的因素——微观结构、力学性能、晶粒大小、载荷系数R、频率、夹杂等做了较详尽的归纳阐述,力求规律,而对另一些外界因素如温度、介质、应力历史等另文详述。 In this paper, we summarize the recent achievements in the literatures about the threshold value and fatigue crack propagation in the vicinity, and study the influence factors of fatigue crack expansion and threshold under low stress-microstructure, mechanical properties, grain size, load coefficient R , Frequency, inclusions and other made a more exhaustive description, and strive for the law, while on some other external factors such as temperature, media, stress history and other details.