中文摘要：

利用已有试验数据，对最大疲劳应变和疲劳残余应变进行拟合，得到疲劳应变演化方程，其相关系数均在0．97以上。考虑到等幅弯曲疲劳加载条件下，疲劳模量与疲劳应变成反比关系，利用对称性，由疲劳应变演化方程得到疲劳模量演化方程，通过拟合试验结果，发现由疲劳模量演化方程表达的拟合曲线与试验曲线吻合很好，其相关系数均在0．99以上。最后，利用疲劳应变与疲劳模量定义损伤变量，得到损伤变量演化曲线，经对比发现，由最大疲劳应变和疲劳残余应变定义的损伤变量演化曲线基本一致，且相差很小：而由疲劳模量定义的损伤变量演化曲线明显大于由疲劳应变定义的损伤变量演化曲线。

英文摘要：

The fatigue strain evolution equation was obtained by fitting the experimental data of the maximum fatigue strain and the fatigue residual strain, and the correlation coefficients were all above 0.97. It was observed that the fatigue modulus was inversely related to the fatigue strain under constant amplitude fatigue loading. Thusly the fatigue modulus evolution equation was obtained according to the fatigue strain evolution equation by use of symmetry. It was found that the fitting curves expressed by the fatigue modulus evolution equation coincided with the experimental curves very well, and the correlation coefficients were all above 0.99. Finally, the damage variable evolution curve was obtained by use of the fatigue strain and fatigue modulus defining the damage variable. It was also found that the damage variable evolution curves defined by the maximum fatigue strain and fatigue residual strain were basically consistent and the deviations were quite small, but the damage variable evolution curve defined by the fatigue modulus was significantly larger than that defined by the fatigue strain.