一、前言疲劳开裂的机理受介质的影响。随着使用材料的强度水平增高,用途增多,因而材料所处的环境也日益苛刻。在这种情况下,对疲劳强度来说,即使是大气也成为严重的腐蚀介质了。大部分结构材料要受到氧和水蒸气的影响,特别是随着能源的开发、海洋开发和宇宙航行的发展,使材料所处的环境更恶劣(例如氢、硫化氢、海水、高温等)。 I. Introduction The mechanism of fatigue cracking is affected by the medium. As materials are used at higher levels of strength and use, the environment in which the material is used becomes increasingly demanding. In this case, even the atmosphere becomes a serious corrosive medium for fatigue strength. Most structural materials are subject to the effects of oxygen and water vapor, especially with the development of energy, marine development and the development of astronautics, making the materials in harsh environments (such as hydrogen, hydrogen sulfide, seawater, high temperature, etc.).