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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。
The existing experimental data were used to fit the maximum fatigue strain and the fatigue residual strain, and the fatigue strain evolution equation was obtained with the correlation coefficients above 0.97. Considering that the fatigue modulus is inversely proportional to the fatigue strain under equal amplitude bending fatigue loading, using the symmetry, the evolution equation of fatigue modulus is obtained from the fatigue strain evolution equation. By fitting the experimental results, it is found that the fatigue modulus evolution equation The fitted curve of the expression is in good agreement with the experimental curve, and its correlation coefficient is above 0.99. Finally, the damage variables are defined by using fatigue strain and fatigue modulus, and the evolution curves of damage variables are obtained. It is found by comparison that the evolution curves of damage variables defined by the maximum fatigue strain and the fatigue residual strain are basically the same with little difference; The evolutionary curves of the defined damage variables are significantly larger than those of the damage variables defined by the fatigue strain.