中文摘要：

针对现有疲劳评价方法存在的问题,引入疲劳特征长度的概念,提出一种新的疲劳理论,该理论既可以统一含不同大小缺陷的疲劳评价问题,也可以很好地说明材料疲劳特性的尺寸依存性问题,并将疲劳极限和裂纹扩展门槛值的评价方法统一起来.通过对各个特征长度内裂纹扩展过程的考察,发现材料的S-N曲线、ε-N曲线和Pairs规律三者之间存在内在关系.通过与文献中的实验结果比较,发现本理论与现有光滑材料、缺陷材料以及疲劳裂纹扩展的评价结果一致.

英文摘要：

A new fatigue theory was proposed by introducing the concept of fatigue characteristic length to deal with the weakness of current fatigue evaluation method.The theory is a unified evaluation method to fatigue problems regardless of the nature and size of the defects.It can also give a reasonable explanation of the size-effect on fatigue properties,and meet the gap between fatigue limit strength and crack propagation threshold.By considering the fatigue behavior of the material within the characteristic length,it is observed that there are intrinsic relationships among the S-N curves,the ε-N curves and the Paris law.Compared with the experimental results,the evaluation results based on the present theory agrees well with the empirical results of materials not only with or without defect,but with crack fatigue propagation.