On the Evaluation and Consideration of Fracture Mechanical Notch Support Within a Creep-Fatigue Lifetime Assessment

Abstract

Changes within the global energy market and a demand for a more flexible operation of gas- and steam-turbines lead to higher utilization of main components and raise the question how to deal with this challenge. One strategy to encounter this is to increase the accuracy of the lifetime assessment by quantifying and reducing conservatisms. At first the impact of considering a fracture mechanical notch support under creep-fatigue loading is studied by discussing the results of an extensive experimental program performed on notched round-bars under global strain control. A proposal of how to consider this fracture mechanical notch support within a lifetime assessment is discussed within the second part of the paper. Here, a theoretical finite element method (FEM)-based concept is introduced and validated by comparing the theoretical prediction with the results of the previously mentioned experimental study. Finally, the applicability of the developed and validated FEM-based procedure is demonstrated.