承受变幅交变应力作用的构件，其疲劳过程是材料逐步受损的过程。本文认为，在经历一定的应力循环后材料承载能力的下降，在用一反映材料当前状态的当量应力来描述，并以当量应力来计算材料的疲劳累积损伤。本方法简便可行，具有较高的准确性，尤其对那些低于材料持久极限的应力循环与材料疲劳寿命之间的关系，作出了定性定量的分析。 To withstand the role of variable amplitude alternating stress components, the fatigue process is the process of gradually damaged materials. This paper argues that the decrease of load bearing capacity after a certain stress cycle is described by an equivalent stress that reflects the current state of the material, and the fatigue cumulative damage of the material is calculated by equivalent stress. The method is simple and feasible with high accuracy, especially for the relationship between stress cycling and material fatigue life, which is lower than the material endurance limit, and qualitative and quantitative analysis is made.