确定飞机结构WFD平均行为的寿命升降法

广布疲劳损伤(WFD)问题严重威胁飞机结构的完整性和安全性,为确定支持飞机结构广布疲劳损伤评定和维修大纲的有效性限制,需要先确定飞机结构的广布疲劳损伤平均行为。以疲劳应用统计学中强度升降法的理论为基础,提出了确定飞机结构广布疲劳损伤平均行为的寿命升降法,在不同寿命级上进行疲劳试验,继而进行剩余强度试验,判断剩余强度是否满足要求,当相邻2个寿命级上出现相反结果时,取2个寿命均值为正好满足剩余强度的寿命,重复试验并统计分析得到广布疲劳损伤平均行为。以5细节多部位损伤结构为例,采用提出的寿命升降法,测得了其在指定载荷条件和剩余强度下的广布疲劳损伤平均行为。提出的寿命升降法以疲劳可靠性为理论基础,不依赖于结构的具体形式和受载情况,对多部位损伤和多元件损伤结构均适用。 

Life up and down method for determining WFD average behavior of aircraft structures

The widespread fatigue damage (WFD) problem is a serious threat to the integrity and safety of aircraft structures.Evaluation of the WFD average behavior is the base for establishing a limit of validity of the engineering data that supports the structural maintenance program. A life up and down method for evaluating the WFD average behavior of aircraft structures was proposed based on the theory of strength up and down method in fatigue applied statistics. The residual strength test was conducted following the fatigue test with a specified fatigue life level (FLL) to determine whether the residual strength meet the requirement. Taking the mean value of the adjacent two FLL with contrasted results as the FLL could lead to a residual strength equal to the required one. By repeating the tests and statistical analysis of the results, the WFD average behavior could be found out. Test on multiple site damage structure with 5-details was conducted with the proposed method, and a WFD average behavior, with a requested residual strength and a specified loading condition, was provided. The proposed method based on the fatigue reliability can be used both in multiple site damage structures and multiple element damage structures, independent of the specific forms of the structures and the load conditions.