Predicting fatigue crack growth under variable amplitude loadings with usage monitoring data

For complex engineering systems, there is an increasing interest in the use of structural health monitoring systems to estimate the current state of damage (diagnosis) and to predict the behavior of the damage in the future (prognosis). For fatigue crack growth, one challenge in prognosis is to predict dynamic stress history at the location of damage. In this article, a method of predicting fatigue crack growth in aircraft panels is proposed under variable amplitude loading. A simple analytical–numerical method is proposed to calculate dynamic stress history from the usage monitoring data. A variable amplitude fatigue analysis is then conducted through the use of a fatigue crack growth model with the extended finite element method. Numerical examples show that the effect of underload and overload is significant in fatigue crack growth. It is also indicated that the crack growth rate and direction can significantly change under the multi-axial loading environment