Advanced Characterization Techniques that Improve Durability of Fracture Critical DoD Components

Many DoD systems employ fracture critical and/or retirement for cause methodologies for asset deployment, operation and management. They are a key element in the design and certification of turbine engines including the F100, F119, and F135. Critical to this approach is the characterization of structural materials and development of life prediction methodologies and application of these to component design, validation and assessment. In structural metallic systems fracture mechanics approaches provide the foundation, however variability and uncertainty are introduced due to the presence of many factors including residual stresses, material variability, complex damage environments, etc. These factors can influence life assessments by factors of four or more. Mission cycles for hot section components such as turbine airfoils are complex and test methodologies such as strain- controlled TMF have not been sufficiently standardized and matured to provide repeatable results across a broad range of facilities and environments. The complex loading profiles these components experience are a further complication. This can lead to reduced durability in key hot section components. The goal of this proposal is to demonstrate the feasibility of newly defined approaches to test specimen thermal gradient management, and thermomechanical cycle time reduction as pertains to strain controlled thermomechanical fatigue testing.