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将Ｗｉｌｌｅｎｂｏｒｇ的超载残余应力场模型与裂尖形变动力学、裂尖表面析氢反应电化学动力学以及裂尖材料内部氢的扩散动力学和热力学相结合，建立了氢脆腐蚀疲劳裂纹扩展（ＣＦＣＧ）超载效应的定量描述模型，给出了超载对裂尖表面析氢电化学反应及裂尖氢扩展影响的一系列判据和表达式．用上述模型进行的预测表明，对于超高强度钢，当两次超载周次之间裂纹扩展长度ａｄ远小于超载塑性区尺寸ｒｐＯＬ与恒载塑性区尺寸ｒｐＣＬＡ之差，即ａｄ＜＜ｒｐＯＬ－ｒｐＣＬＡ时，ＣＦＣＧ会发生比空气疲劳还强烈的超载迟滞效应．而当ａｄ＞ｒｐＯＬ－ｒｐＣＬＡ时，可能会发生超载加速效应．这种预测在后文中由试验的宏观规律与断口特征得到充分验证．

A quantitative descriptive model was developed theoretically of the effects of overloading on corrosion fatigue crack growth (CFCG) of hydrogen embrittlement type. This is based on the comprehensive combination of the Willenborg' overloading residual stress field model with the following knowledge of the process of CFCG: crack tip surface deformation kinetics, the crack tip surface hydrogen evolution kinetics, and the hydrogen diffusion kinetics and thermodynamics in crack tip metal matriX interior. A series of criteria and equations were correspondingly deduced. Furthermore, this model has been used to predict the effects of overloading on CFCG. The results suggest that for ultra-high strength steel, if crack length, ad, grown during the interval of two overloading cycles, were smaller than the difference betwere the overloading plastic region size, rpOL,and the constant loading plastic region size, rpCLA,i. e. ad << rpOL-rpCLA,the retardation effect of overloading on CFCG would be more intensive in 3.5%NaCl solution than in air;on the contrary, if ap≥rpOL-rpCLA, the acceleration effect of overloading on CFCG would occur. It is note-worthy that the overloading acceleration effect does not occur for fatigue in air. The correctness and usefulness of these predicted results have been favourably proved by the macroscopic experimental laws and microscopic fractographic characteristics, the details of which will by presented in the next paper.