An Overview of creep-fatigue damage evaluation methods and an alternative approach

Asayama, Tai ; Jetter, R.*

Renewed interest in elevated temperature nuclear reactors has occasioned a reassessment of creep-fatigue damage evaluation methods. Points to be improved in the current methods employed in Subsection NH of the ASME Boiler and Pressure Vessel Code and other design codes are discussed. Most current creep-fatigue damage evaluation methods separately evaluate cyclic fatigue damage and creep damage and assess the combined damage through interaction diagrams. In this paper, an alternate approach to determination of cyclic life has been proposed which avoids parsing the damage into creep and fatigue components. This approach, called the Simplified Model Test (SMT) has two major advantages. First, it is not necessary to calculate the inelastic stress-strain history for a design evaluation. Second, it is not necessary to rely on theoretical modeling of these effects in an artificial separate accounting of creep and fatigue damage.