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Vol.50, No.4, 271 ~ 280, 2012
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| Title |
| Effects of Temperature and Stress Ratio on Low-Cycle Fatigue Crack Growth of G91 Steel |
| 김종범 Jong Bum Kim , 황수경 Soo Kyung Hwang , 김범준 Bum Joon Kim , 이종훈 Jong Hoon Lee , 박창규 Chang Gyu Park , 이형연 Hyeong Yeon Lee , 김문기 Moon Ki Kim , 임병수 Byeong Soo Lim |
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| Abstract |
| 9-12% Cr steels have been used in thermal power plants which repeat start and stop operations. Major factors of fatigue life are temperature, frequency, stress ratio, holding time, microstructure, and environment. Normally, fatigue life decreases at high temperature, low frequency, high stress ratio, and long holding time conditions. A Mod.9Cr-1Mo steel, called G91, was developed at ORNL (Oak Ridge National Laboratory, USA) and was adopted as a high-temperature structural material in the ASME Code in 2004. However, its low-cycle fatigue and fatigue crack growth characteristics have been rarely studied. In this work, we have investigated the low-cycle fatigue crack growth behaviors of G91 steel under various test conditions in terms of temperature and stress ratio. As temperature and stress ratio increase, the crack growth rate becomes faster and striation distance also increases. On the other hand, the number of branch cracks decreases. |
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| Key Words |
| fatigue crack growth, high temperature fatigue, G91, stress ratio, branch crack, striation |
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