Three-Dimensional (3-D) Crack Growth Life Prediction for Probabilistic Risk Analysis of Turbine Engine Metallic Components

ABSTRACT: Over the past few years, the Air Force has increased the emphasis on probabilistic methods for design reliability predictions of fracture critical engine components, including metallic turbine engine blades and disks. A significant shortcoming and potential source of conservatism of most current life prediction tools and methodologies is the reliance on stress intensity factor values obtained from highly idealized component and crack geometries. In Phase I, we demonstrated that this shortcoming could be overcome by making an existing high fidelity 3D crack growth simulator work together with an existing probabilistic life prediction code. The resulting prototype software tool was used to perform a probabilistic life prediction for a geometrically complex engine component. For Phase II, we propose to develop the prototype software into a tool suitable for routine production use. This will include creating a unified graphical user interface, adding additional features, performing sensitivity studies that will assess accuracy/efficiency tradeoffs and develop best practices, and performing a series of analyses that include advanced life prediction topics. BENEFIT: The successful completion of Phase II will result in a high fidelity probabilistic fatigue life prediction tool for metallic turbine engine components. Such a tool will allow engine manufacturers to reduce uncertainty and conservatism in fatigue life assessments. This means that for current engine designs, component lives or inspection intervals can be extended with no increased risk of failure. For new engine designs, the tool can be used to help find the optimal point among performance, efficiency, and life cycle cost. The tool can be used by the government to perform high accuracy fracture risk assessments independent of the manufacturers. The tool can also be applied to other applications with fracture critical components, such as airframes and power generation turbines, among others.