结构和载荷谱分散性分离的疲劳寿命可靠性

机群疲劳寿命的分散包含了结构和载荷谱的分散性,为进行安全寿命的精细分析,将结构和载荷谱的分散性进行了分离。假定指定载荷谱下的疲劳寿命和指定结构下载荷谱分散均用对数正态分布描述,按条件概率模型推导得到了将载荷谱和结构分散性综合后的机群结构疲劳寿命的精确分布,其数学期望与指定结构下考虑载荷谱分散的数学期望相同,方差为载荷谱和结构分散的方差和。从而可以采用反映载荷严重使用情况的载荷谱和仅考虑结构分散性的小分散系数确定结构的安全寿命,并讨论了给定的可靠度指标下,严重谱的严重程度要求以及给定的严重谱下的结构寿命可靠度。

Reliability Analysis on Fatigue Life with Separated Structural and Load Spectrum Scatters

To assess the safe-life for a fleet, and account for the effects of load spectrum variability, the fatigue life scatter including the load spectrum scatter and structural property scatter is separated. It is assumed that the fatigue life under the specified load spectrum follows the log-normal distribution, and that the load spectra damage also follows the log-normal. The fatigue life scatter is separable, and then the accurate distribution function of the fatigue life is deduced with the conditioned probability model. The expectation is unchanged, and the variation is equal to the sum of the structural variation and the load spectrum variation. Therefore the safe-life of a fleet can be determined by the small scatter factor under a severe spectrum, and the spectrum severity and the life reliability are discussed.