Joseph David Rigney

Cumulative Damage Modeling for Nickel-Based Superalloys Under Creep and Fatigue Loading

Turbine blades operating in aircraft engines are subjected to complex thermomechanical conditions that include a combination of very high temperatures, high stresses and aggressive oxidizing environments. As a result, such components can simultaneously experience damage from creep-, fatigueand oxidation-related mechanisms. Selected literature models were evaluated in their capability to predict the performance of single crystal nickel-based superalloys over a wide range of test conditions. Because existing models were not sufficiently accurate for commonly used superalloys such as Rene N5, a new cumulative damage model (CDM) was developed to account for the broad range of complex stress conditions and mission strain-temperature histories that can be experienced. The predictive capability of CDM has been assessed with solid and tubular specimens tested under both simple and complex thermal-mechanical conditions. The new modeling approach was also validated on test plans designed to be representative of a cooled, thin walled component loaded under engine-simulative conditions.