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在飞机结构设计定型阶段,要综合考虑结构的差异和载荷的分散性评定机群的安全寿命。美国空海军联合规范指南JSSG-2006、标准MIL-STD-1530C和我国国军标GJB67.6A-2008提出采用90%谱(严重谱)进行飞机结构耐久性分析和试验,但并未给出严重谱严重程度的选取准则。该文以机群载荷损伤分散描述机群载荷分散,初步探讨了载荷谱严重程度的选取方法。假定指定谱下的结构寿命和机群载荷损伤均服从对数正态分布,在综合载荷损伤和结构分散性的寿命分布基础上,分析了严重谱下的寿命可靠度。按机群安全寿命满足99.9%的可靠度要求,以载荷损伤覆盖概率描述载荷谱严重程度,给出了载荷谱严重程度的表示形式,并针对典型的飞机结构分散和载荷损伤分散性参数,给出了典型的载荷损伤覆盖概率取值。分析表明严重谱的严重程度与载荷损伤分散性和结构分散性均有关,基于损伤的90%严重谱可以保证机群内超过99%飞机的使用安全。
At the stage of aircraft structural design, it is necessary to evaluate the safety life of the fleet considering the structural differences and the dispersion of loads. The United States Air Naval Unification Guidelines JSSG-2006, Standard MIL-STD-1530C and China’s National Military Standard GJB67.6A-2008 proposed the 90% spectrum (severe spectrum) for aircraft structural durability analysis and testing, but did not give serious Spectral Severity Selection Criteria. In this paper, the cluster load dispersion is described by the damage of cluster loads, and the selection of the severity of the load spectrum is discussed preliminarily. Assuming that both the structural lifetime and the cluster load damage under the specified spectrum obey the logarithm normal distribution, the reliability of life under severe spectrum is analyzed based on the life distribution of the integrated load damage and structural dispersion. According to the reliability requirement of 99.9% of the fleet life expectancy, the severity of the load spectrum is described by the coverage probability of the load damage, and the representation of the severity of the load spectrum is given. For the typical aircraft structural dispersion and load damage dispersion parameters, A typical load damage coverage probability value. The analysis showed that the severity of severe spectrum was related to the damage distribution and structural dispersibility of the load. Based on the 90% severe spectrum of damage, the safety of over 99% of the aircraft in the cluster could be guaranteed.