飞行器结构疲劳寿命分散系数理论值确定的一种方法

A Better Method for Determining Fatigue Scatter Factor of Aircraft Structures

提出了一种基于假设检验观点的确定疲劳寿命分散系数理论值的方法。针对疲劳寿命服从对数正态分布和威布尔分布的情况 ,分别推导了基于假设检验观点的分散系数确定公式。算例表明在小子样容量条件下 ,与传统的参数估计概念的分散系数相比 。

Traditionally aeronautical engineers determine fatigue scatter factor S f with the concept of parameter estimation and usually obtain the value of S f much higher than its actual statistical value. We propose using the new concept of hypothesis test to determine fatigue scatter factor S  f that is closer to its actual statistical one. Our new method considers reliability, confidence level, and sample size; we emphasize especially making full use of the data of previous tests for ensuring the total survival probability of serial products. We derived formulas for calculating S  f for two generally accepted fatigue life distributions: eqs. (1) through (4) for lognormal distribution and eqs. (6) through (10) for Weibull distribution. Calculated results in Table 1 (lognormal distribution) and Table 2 (Weibull distribution) do show preliminarily that S  f is closer than S f to the actual statistical fatigue scatter factor.