Coupled Corrosion and Fatigue Lifing Tool for Aero-Propulsion Components

Naval aircraft propulsion systems are subjected to the combined action of environment and mechanical usage that limit component life. These coupled effects make lifing aero-propulsion components challenging.  Predicting the component lives requires an extensible, coupled corrosion and fatigue lifing tool that can account for the material and usage interaction effects. This tool will combine the effect of corrosion into a total and remaining fatigue lifing tool for aero-propulsion components to inform fleet management.  The model will create S-N curves from predictions of the initiation and propagation stages of component life while incorporating usage severity, corrosion damage, and small crack kinetics to achieve a comprehensive lifing tool.  Corrosion damage will be predicted to inform the initiation life of a crack.  Predictions of when a corrosion pit is significantly large enough to initiate a propagating crack will be made using a modified Kitagawa-Takahashi (K-T) diagram, where the significant pit size will be sensitive to the effects of the fatigue loading, environment, and geometry of the modeled component.  The propagation life will be predicted by incorporating the geometry of the corrosion damage and the kinetics of active corrosion into a fracture mechanics model.