Abstract
With the expansion of clean energy, thermal power plants will be used as a load-following power plant. Thus, temperature and strain variations will occur during load fluctuations including start and stop of operation, and large-diameter pipes will be damaged by fatigue in addition to creep due to internal pressure. Especially, in a bent pipe such as an elbow pipe, bending and torsion are simultaneously applied. Therefore, it is important to predict the creep fatigue life in a bending and torsional stress environment. In this study, analysis method for creep fatigue life using Norton's law, ductile exhaustion law, and Manson-Coffin's law is proposed. Next, the proposed method was applied to the prediction of creep fatigue life of the test samples for thermal power plant piping, and the validity of the proposed method was verified by comparing creep fatigue life obtained by proposed method and that obtained by an experiment. In addition, the proposed method is applied to the prediction of creep fatigue life with load fluctuations and investigation of the effects of load fluctuation interval on creep fatigue life.
