Assessment on Strain-Based and Stress-Based Design Strategies for Components at Elevated Temperatures: A Comparative Study

Geometrical discontinuities (such as holes and grooves) widely exist in many components, which operate at elevated temperatures. Creep assessment of the geometrical discontinuities is essential for the safe operation of the system. In general, creep evaluations are conducted from the stress-based and strain-based strategies, but comparative studies on the extent of conservatism of these two design strategies are rarely included. In this work, creep test data of the notched components made of 9–12% Cr steel conducted by authors and that of 9Cr–1Mo steel collected from published works are employed for comparative evaluations. Results indicate that strain-based and stress-based strategies are both relatively conservative for notches in metal materials, and the conservatism of the assessment strategies increases with the notch acuity ratio of the component. The differences of the conservatism for strain-based and stress-based strategies are dependent on the notch acuity ratio and the ductility of the materials. For a blunt notch, the strain-based strategy is more conservative than the stress-based strategy for materials mentioned, while the dominant assessment strategy is dependent on stress redistribution performances of components with a sharp notch.