基于Fokker 27飞机过载-超越数曲线族的严重超越数包线选取

 以Fokker 27机群的过载-超越数曲线族为基础,建立了严重谱对应的严重超越数包线的获取方法。首先对外场使用的Fokker 27飞机机群的过载-超越数曲线进行筛选,得到59架飞机的过载-超越数曲线,采用线性累积损伤理论计算得到59架飞机每次飞行的损伤;假定机群载荷损伤服从对数正态分布,以严重谱下安全寿命满足机群寿命可靠度要求为准则,给出了严重谱的损伤程度。其次,采用对数正态分布描述指定过载下超越数的分布特性,外推得到满足损伤要求的严重超越数包线及对应的概率要求。结果表明,Fokker 27飞机严重过载-超越数曲线包线对应的超越数增量为1.117倍标准差。

A Method for Determining the Exceedance Envelope of Severe Spectrum Based on the Acceleration-exceedance Curves of Fokker 27 Airplanes

To develop the severe spectrum, a method for determining the exceedance envelope of a severe spectrum is proposed based on the analysis of the exceedance curves of a fleet of Fokker 27 airplanes. First, the exceedance curves of 59 airplanes with similar service methods are selected, and the damage per flight of the fleet is calculated on the basis of the accumulated linear damage theory. Assuming the damage per flight of the Fokker 27 fleet follows the log-normal distribution, the damage degree of the severe spectrum is obtained according to the reliability requirement on the safe life of a fleet. Next, a log-normal distribution is used to depict the scatter of exceedance under a specified acceleration. Thus, an exceedance envelope of the severe spectrum is obtained by the extrapolation of the exceedance curve. The analysis shows that the exceedance of the severe spectrum should be increased with 1.177 times of its standard deviation.