An indicator of the reliability of analytical structural design

Abstract

A statistical analysis of structural static failure data for major components of aircraft is presented. The data sample is divided into the static failures of wings, fuselage, horizontal stabilizer, vertical stabilizer, and landing gear. The analysis results in the approximate determination of the specific statistical strength density function and cumulative distribution as a function of the rupture strength. Finally, the required factor of safety is computed for the static test or analytical design case for the aforementioned components over a wide range of unreliabilities. It is concluded that components require factors of safety for the no static or analytical design approximately an order of magnitude above the usual standard and would be prohibitive if implemented. Nomenclature a — statistical parameter in truncated Weibull distribution b = statistical parameter in truncated Weibull distribution F — function m = inverse of the factor of safety P = probability distribution function R = reliability S = strength x — strength or load variable 7 = (= cr/V) scatter coefficient or coefficient of variation = normal probability density function <£ = normal cumulative probability function