Components in the hot section of a gas turbine experience both load cycles and high temperature dwells as the engine is subjected to starts, changes in load, dwells and shut downs. These loading profiles can lead to damage from both fatigue and creep and can also lead to the interaction of these two damage mechanisms over the duration of the service interval. Accurate prediction of the accumulation of this damage is critical to managing the engine and avoiding unplanned down time and cost over the operational period.
Ductility Exhaustion uses the rate dependent ductility of a material to determine damage from creep and fatigue. This approach can be used to calculate damage during shakedown as a result of redistribution and relaxation due to plasticity and creep, and can be critical for accurately predicting the remaining useful life of hot section components subjected to variations in load.
This paper presents a modification to an existing approach in order to address the effects of mean stress on upper shelf ductility and improve the accuracy of the damage prediction during shakedown. The approach, based on two common superalloys, predicts how damage accumulated during the initial shakedown period can be modified to account for mean stress effects. Thereby improving the accuracy of the overall component life prediction for optimal engine management.