基于对数正态分布的多部位疲劳结构的疲劳寿命预测方法

Fatigue life prediction method for multi-site fatigue structure with lognormal fatigue life

以实现多部位疲劳结构的寿命预测为目的,基于概率累积损伤法则,推导了基于寿命服从对数正态分布的概率疲劳寿命预测方法。根据损伤临界值与应力水平无关这一前提条件,将损伤临界值由传统确定性的值1转换为随机变量,累积损伤由确定性的中值损伤计算,建立了"中值累积损伤-概率损伤临界值"干涉模型。当对数寿命标准差恒定时,对比了所提出模型和基于Monte Carlo仿真的Miner累积损伤方法的寿命预测结果,验证了模型的准确性以及其方便快捷的优点;当对数寿命标准差变化时,损伤临界值由满足损伤等效的应力基准决定,此时亦可得到高精度的偏于安全的寿命预测结果。

To predict the fatigue life of multi-site fatigue structure, a probabilistic fatigue life prediction method based on the probabilistic accumulated damage rule is proposed, considering that fatigue life obeys Iognormal distribution. According to the precondition that the damage critical value is independent of stress level, the damage critical value is transformed from the traditionally deterministic value 1 into a random variable, and the accumulated damage is calculated by the median S-N curve. An accumulated damage-probabilistic damage critical value interference model is thus built. When logarithmic fatigue life standard deviation is constant, life prediction result of the proposed interference model is compared with that of the Miner accumulated damage model based on Monte Carlo simulation. The comparison result verifies accuracy and efficiency of the proposed model. When logarithmic fatigue life standard deviation is varied, the damage critical value is decided by damage equivalent stress, and a high-precision and safer life prediction result can be gained.