2.25Cr-1Mo鋼環状切欠き試験片のクリープ損傷過程と破断時間予測法

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. Rupture times of notch specimens were much longer than those of plane specimens under the same nominal stress indicating notch strengthening effect. Measured void number density on the notch root section indicated higher value at around notch surface for R0.1 and R0.5 specimens, while it was higher at around specimen center for R2.0 and R4.0. These distribution patterns corresponded to those of the maximum stress and the triaxiality factor of the notch specimens. Although, creep rupture times of notch specimens were not able to be predicted by using the stress or strain at the representative point on the notch root section, they were well predicted based on the area average damage concept, especially by considering selected damage area for R0.1 and R0.5 specimens.