RECENT DEVELOPMENT IN FATIGUE DAMAGE AND CRACK GROWTH ANALYSIS: VERIFICATION AND VALIDATION, AND APPLICATION IN LIFING AIRFRAME STRUCTURES

摘要

Integral to aircraft structural integrity management in the Australian Defence Force is the requirement for fatigue analysis to ensure the safe operation of its aircraft. As such the Defence Science and Technology Organisation have been conducting applied and enabling research into the mechanisms driving the fatigue process in metallic structures. Through a deepened understanding of these mechanisms the Defence Science and Technology Organisation aims to develop and improve the accuracy of algorithms to model the fatigue process. To support the Australian Defence Forces objectives an in-house computer program, known as CGAP, has been developed. This software has been designed to be an intuitive interface for a range of fatigue analysis tools. Among CGAP's fatigue analysis capabilities are tools for predicting fatigue crack initiation life and crack growth. The user can easily interact with these tools via a standard graphical user interface based on the Microsoft Windows operating system, an integrated database for material properties and geometry factors, and a batch processing capability. The fatigue crack initiation module in CGAP is based on the strain-life approach, and the crack growth modules are based on the concept of plasticity-induced crack closure. The CGAP solver for crack growth not only provides all the functionality of FASTRAN, which is also supported, but also provides advanced capabilities for probabilistic crack growth and analysis of crack growth in notch-affected plastic zones. To complement these capabilities several other useful tools have been developed and included to enable efficient and effective fatigue analysis. This paper summarises some of the recent developments in analytical and numerical fatigue damage and crack growth modelling, with emphasis on the relevance to applications to the Australian Defence Force.