J0310201 CrMoV鍛鋼環状切欠き材のクリープ損傷評価

Abstract

Creep damage preferentially proceeds at stress concentrated portion such as notch roots under multiaxial stress states in high temperature components. It is necessary to establish creep damage assessment methods under these conditions for maintaining safety operation. So far, influence of notch on creep rupture strength, and damage condition at notch root after testing were reported. However, damage extension process at notch root is not clarified and argument of damage assessment methods is still on going. In this study, creep tests were carried out using the circumferential notch specimens on a CrMoV forging steel. Damage conditions at the notch root were observed with interrupted test specimens. Damage assessment by using the miniature creep specimens taken from damaged notch specimens was conducted. It was found that the location where the void number density is the largest is corresponding to the location where both the axial stress and the triaxiality factor yield the maximum values. The creep damage given to the notch specimen was underestimated by the subsequent miniature creep test, when creep voids initiated in the creep damaged specimen do not give any influence on ductility reduction for the miniature specimen.