独立多细节结构耐久性试验寿命的统计标定

在进行疲劳试验评定结构寿命时,为了能真实模拟实际结构形式和传载情况,模拟试件往往设计成多细节试件,进行不完全疲劳寿命试验,必须由多细节试件寿命推断单细节寿命.针对工程上常用的两种寿命分布形式:对数正态分布和双参数Weibull分布,以结构串联失效模型为基础,建立了由相同独立多细节结构疲劳寿命分布确定单细节寿命分布的统计标定方法.当多细节试件寿命服从对数正态分布时,可近似认为单细节寿命也服从对数正态分布,单细节寿命分布参数与多细节试件寿命分布参数间存在确定关系,并且单细节寿命数学期望和标准差均高于多细节试件相应参数;当多细节寿命服从双参数Weibull分布时,单细节寿命也服从双参数Weibull分布,其斜率不变,但位置参数按比例放大.最后给出了一个分析实例.

Statistical scaling of durability life for independent multi-detail structures

To assess the fatigue life for aircraft structure,the specimen used for the durability test is often designed as multi-details(MD) to simulate the structural configuration and load transfer.Once one detail fails,the fatigue testing is ended,and the fatigue life of single detail(SD) must be deduced statistically based on the incomplete life of MD specimen.Based on the series failure model of the same multi-detail structures,the statistical scaling approach was proposed to determine the life distribution of the single detail.Assuming the fatigue life of MD follows the log-normal distribution,Monte Carlo sampling and stimulating results show that the fatigue life of single detail follows the same distribution approximately;the expressions between the distribution parameters of MD and SD are deduced.The expectation and variation of MD are higher than those of SD.Assuming the fatigue life of MD follows the two-parameter Weibull distribution,the SD’s fatigue life follows the same distribution whose slope is unchanged,but location parameter is larger than that of MD.Finally,an example for analyzing MD fatigue test result from American durability test program is given.