Characterization of creep-fatigue crack growth behavior under trapezoidal waveshape using C
t
-parameter |
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| Authors: | Kee Bong Yoon Ashok Saxena Peter K Liaw |
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| Affiliation: | (1) School of Materials Engineering, Georgia Institute of Technology, 30332 Atlanta, Georgia, USA;(2) Present address: Korea Standards Research Institute, 305-606 Taejon, Republic of Korea;(3) Present address: Westinghouse Science and Technology Center, 15235 Pittsburgh, Pennsylvania, USA |
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| Abstract: | An experimental study of creep-fatigue crack growth behavior of 1.25Cr-0.5Mo steel at 538°C (1000°F) under trapezoidal loading waveshapes has been carried out on compact type specimens. In creep-fatigue crack growth experiments, hold times ranged from 0 seconds to 24 hours with intermediate conditions of 10 seconds, 98 seconds, 10 minutes and 15 minutes. Time-dependent crack growth rate during the hold period, (da/dt)avg, is correlated with (C
t
)avg. The values of (C
t
)avg are estimated using the equation recently proposed for elastic-cyclic plastic-secondary creeping (EL-CPL-SC) materials. The (da/dt)avg vs. (C
t
)avg data fall on a single trend which matches with the trend of da/dt vs. C
t
creep crack growth data for the same material. A model is proposed for predicting both the creep crack growth behavior and the creep-fatigue crack growth behavior. The model is suitable for assessing the residual life and/or the safe inspection intervals of high-temperature components such as steam headers. Transition of crack tip damage patterns from oxidation to creep cavitation across the range of hold times examined is also discussed. |
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