多軸応力勾配を有する2.25Cr-1Mo鋼のクリープ破断時間予測法

抄録

Creep damage preferentially progresses at stress concentration portion, where stress gradient exists under multiaxial stress state, in high temperature components. Therefore, it is necessary to clarify creep damage evolution process and to establish a rupture time prediction method under multiaxial stress state. In this study, creep tests using plane specimens and four kinds of round notch bar specimens with different notch radius (notch tip radius 0.1mm(R0.1), 0.5mm(R0.5), 2.0mm(R2.0) and 4.0mm(R4.0)) on a 2.25Cr-1Mo steel were carried out. Creep rupture times of the notch specimens were longer than those of plane specimens. Greater number of voids were observed at 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 and R4.0. The finite element creep analysis of the notch specimens showed that triaxial tensile stress yields at the notch root sections with different distribution of the triaxiality factor depending on the notch radius. Creep rupture times of four kinds of round notch bar specimens were accurately predicted by the area average creep damage evaluation method.