基于自助法的小样本疲劳寿命试验D32钢P-S-N曲线确定

DETERMINATION OF THE P-S-N CURVE OF D32 STEEL WITH FATIGUE LIFE TEST OF SMALL SAMPLE BASED ON THE BOOTSTRAP METHOD

材料疲劳寿命试验确定其疲劳曲线常常是一种小样本情况,而确定材料P-S-N曲线需要大样本估计疲劳寿命概率特征值。为了解决这样问题,将增广样本统计方法—自助法应用于小样本疲劳寿命试验P-S-N曲线确定,并理清了其计算过程,解决了小样本情况下其概率特征值的不稳定性问题。基于D32钢的疲劳寿命试验数据,将方法应用于D32钢P-S-N曲线的确定,得到了D32钢P-S-N曲线,并与各级应力水平疲劳寿命样本集成总体法计算的结果比较,得到了一些有用的结论。

The sample size of material fatigue test to determine the fatigue life curve is often small. Based on the probability characteristic values of large sample size of the material fatigue life the P-S-N curve can be determined accurately. To overcome the difficuhy that the accurate P-S-N curve can＇ t be obtained from small sample of test data, the Bootstrap method of expanded sample statistical is applied to determine the P-S-N curve from the small sample test, and corresponding calculation procedure is established which solved the instability of the probabilistic characteristic value of the small sample size. According to the fatigue life data of D32 steel, the P-S-N curve determined by this method is compared with those determined by the traditional methods. The results show that the present method is more accurate than the traditional method of integrating sample of all fatigue lives under different stress levels.