Modified Joint Weibull approach to determine Load Enhancement Factors

Load Enhancement Factor (LEF) and similar statistical methods have been used for decades to reduce the time and cost associated with component-level fatigue testing on aerospace structures. The most common LEF approach was that developed by the Naval Air Development Corporation in the 1980s. Though considered an innovative and novel concept at its conception, this traditional method has a number of limitations that restrict its applicability to only a handful of testing scenarios. The objective of this study was to deal with those restrictions and offer a more comprehensive approach to account for modern advances in statistics, composite materials, and testing technology. The formulation of the new method uses the traditional LEF method as a foundation, but uses a revised set of notation and incorporates a modified Joint Weibull analysis technique to improve its potency. A detailed set of sample calculations using stochastically generated data illustrates how the computations are performed, thus allowing practitioners to reproduce the method using their own data. A short discussion also addresses some common misconceptions regarding the use of Load Enhancement Factors.