基于威布尔分布的C-T曲线通用性分析

为研究载荷谱、恒幅应力水平及裂纹尺寸对疲劳寿命预腐蚀影响系数C(T)的影响,建立了基于疲劳寿命服从威布尔分布的C(T)对比法.地面停放预腐蚀对结构疲劳寿命的影响规律可以用C-T曲线表示,当预腐蚀疲劳寿命位于长寿命段,常假定其服从威布尔分布,C(T)为预腐蚀后和未腐蚀结构特征寿命的比值.取预腐蚀疲劳寿命分布函数的形状参数为材料常数,采用极大似然方法估计特征寿命,得到其分布特性,从而建立了C(T)估计量的分布特性,构造了不同环境下的C(T)统计对比法,用于C-T曲线通用性分析. 试验数据分析表明,当取疲劳寿命服从威布尔分布时,C-T曲线与载荷谱、应力水平及裂纹尺寸基本无关.

Generality analysis of the pre-corrosion influence on the fatigue life for aircraft structure

To analyze the influence of the different spectra loading,constant amplitude loading and crack size on the pre-corrosion influence factor(C(T)),the C(T) test assuming the fatigue life following the two-parameter Weibull distribution was proposed.The C(T) shows the pre-corrosion influence on aircraft structural life under different ground parking time is the ratio of pre-corrosion characteristic life to un-corrosion characteristic life when the pre-corrosion fatigue life located in the long life range.Assuming the slope of the Weibull distribution is material constant,and the unbiased characteristic life which was estimated with the maximum likehood estimation(MLE),the probability density function of the estimator was determined.The distribution function of the statistic C(T) was obtained,the C(T) contrast approach was proposed,and used to test the hypothesis that the C-T curve is general between different spectra loading,constant amplitude loading and crack size,the fatigue testing data shows that the C-T curve is weak-correlation with these influence factors.