Abstract
Modified 9Cr-1Mo steel is now being used for high-temperature structural components on a world wide scale because it has an extremely high allowable stress. In the design of high-temperature equipments, the prevention against creep-fatigue failure is an essential problem. However, the method of creep-fatigue life prediction has not been clarified for modified 9Cr-1Mo steel. In the creep-fatigue design of structural components, an inelastic analysis is often used when their service conditions are severe. And in such case, the estimated life is affected not only by the accuracy of a life prediction method but also by the accuracy of an inelastic analysis. Therefore, both of these accuracy should be taken into consideration to establish a rational creep-fatigue design method.
In this paper, the method of life prediction by the linear damage rule for modified 9Cr-1Mo steel was investigated in the viewpoint of both the inelastic analysis and the damage evaluation. The results show that the effect of loading history should be considered both in stress-strain properties used for inelastic analysis and in creep-rupture properties used for creep damage evaluation in order to make a rational prediction.
