Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : September 09, 2018 - September 12, 2018
Creep damage preferentially extends at a stress concentration portion in components such as steam turbine. Therefore, in order to maintain reliable operation, it is necessary to clarify the relationship between the creep damage process and the stress states in the stress concentration portion. In this study, creep tests using three kinds of round bar notch specimens (notched tip radius 0.1 mm (R0.1) and 0.5 mm (R0.5) and 2.0 mm (R2.0)) with different notch radius on a Modfied 9Cr-1Mo steel have been conducted to clarify influence of stress conditions on creep damage extension process. Creep rupture times of the round bar notch specimens were longer than those of plain specimens. Greater number of voids was observed around 0.1 mm from notch root in R0.1, and around 0.5 mm from notch root in R0.5, and around center of the specimen in R2.0. Finite element creep analyses of notch specimens indicate that triaxial tensile stress yields at the notch root sections with different distributions of the triaxiality factor depending on the notch radius. A new creep rupture time predicted method was proposed, in which the triaxial factor was taken into account in the equivalent a stress. Creep rupture times of three kinds of round bar notch specimens were accurately predicted by the proposed method.
