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本文基于损伤函数和五维应变偏量空间的加载路径,导出了非比例加载下材料的损伤度大于比例加载下的损伤度,论证了Miner线性累积损伤律不适于非比例加载情况及由它所得结构寿命偏高、偏危险的结果。作为工程应用,导出了在两种非比例加载情况下扭转低周疲劳的损伤方程及寿命算式;进而对不同频率的谐波应变迭加情况导出了损伤方程,并对高周与低周加载的复合疲劳得出了寿命算式。计算结果与文献[3]、[9]的实验结论相符。
Based on the damage function and the loading path in the five-dimensional strain offset space, the damage degree of material under non-proportional loading is larger than that under proportional loading. It is proved that Miner’s linear cumulative damage law is not suitable for non-proportional loading and Structural life is high, partial dangerous result. As an engineering application, the damage equation and the life equation of torsional low cycle fatigue under two kinds of non-proportional loadings are deduced. Then the damage equations are derived for the superposition of the harmonic strains at different frequencies, Composite fatigue has come to life formula. The calculated results are consistent with the experimental conclusions of [3] and [9].