Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : September 13, 2020 - September 16, 2020
Modified 9Cr-1Mo steel is used for the steam turbine rotors because of its superior high-temperature property. Creep-fatigue damage progresses preferentially at stress concentration portions in the steam turbine rotors. In this study，creep-fatigue tests using round notch bar specimens on a modified 9Cr-1Mo steel have been conducted to clarify effect of multiaxial stress conditions on failure life. The failure life of round notch bar specimen was much shorter than that of plain specimen under the same nominal stress conditions. From observation of notch root of the creep-fatigue damage specimens，it suggested that most of the creep fatigue life was occupied by crack propagation up to 1mm from the notch root surface. A new creep-fatigue life evaluation method of round notch bar specimens，in which concept of a damage evaluation area was introduced，was applied. As a result，creep-fatigue lives of the round notch bar specimens were accurately predicted by applying the new procedure with the nonlinear damage accumulation rule.
