FUZZY VARIABLE AND PROBABILISTIC METHODS APPLIED TO FATIGUE AND CRACK PROPAGATION IN AGEING AIRFRAME STRUCTURES

摘要

Ageing platforms form an increasing part of the fleets of the UK and other armed forces. Each of these platforms has been designed for a particular life under a specific loading spectrum. In reality, each individual aircraft will be different due to variance in usage, loading, environmental degradation, material and manufacturing characteristics. Probabilistic methods can take into account the variability in loading, material characteristics, environmental damage and manufacturing concessions on structural performance. This paper describes the development and application of fuzzy variable and probabilistic methods for fatigue analysis and crack propagation. The paper concentrates on including the effects of uncertainty into crack propagation. This is achieved by using the USAF code AFGROW to integrate the crack growth equations and linking this to in-house fuzzy variable codes and DAKOTA for probabilistic analysis. Linking is achieved using a combination of visual basic code and file wrappers in the Phoenix Integration ModelCenter code. The method is illustrated using an analysis of a generic transport aircraft wing.