Abstract
Heat exchangers manufactured from Inconel 690 tubes are widely used for steam generators in nuclear power plants. Inconel 690 tubes have suffered failures of fatigue fracture due to flow induced vibration. It is difficult to obtain the fatigue life of the tube directly since the conventional fatigue test would potentially cause end fatigue failure due to the stress concentration at the clamp end. In this study, a thin-walled Inconel 690 tube with circular hole is designed to deduce the fatigue life of smooth tube based on the notch fatigue life prediction technology. Firstly, the local stress and strain distributions around the hole based on the finite element analysis are discussed. Local stress-strain is calculated and compared with Neuber’s ruler. Meanwhile, fatigue life tests using tube specimens with circular holes are carried out. Finally, based on the best-fitted fatigue life curve of Inconel 690 alloy, the fatigue life of tube specimen is estimated from the local strain according to Neuber’s ruler. The results show that the local stress and strain estimated by Neuber’s ruler are basically consistent with those obtained by finite element analysis. Compared with the average fatigue life of nickel-based alloy, the new predicted equivalent fatigue life of heat Inconel 690 transfer tube with a hole is higher. The Inconel 690 heat transfer tube has better fatigue performance.
Highlights
Inconel 690 heat transfer tubes, with excellent heat transfer performance, have been widely used in nuclear steam generators, ultra-supercritical boilers, and other important equipment in nuclear power plants
The heat transfer tube is subject to many degradation mechanisms, e.g., corrosion, wear, and fatigue
It should be noted that fatigue failure of tubes must be considered during the design and operation of steam generators
Summary
Inconel 690 heat transfer tubes, with excellent heat transfer performance, have been widely used in nuclear steam generators, ultra-supercritical boilers, and other important equipment in nuclear power plants. The heat transfer tube is subject to many degradation mechanisms, e.g., corrosion, wear, and fatigue. It should be noted that fatigue failure of tubes must be considered during the design and operation of steam generators. Fatigue design curve is necessary to conduct the fatigue design of tubes, which is usually derived from large tests of similar materials under atmospheric environment. To consider the effect of corrosion degeneration, a correction factor is usually adopted to revise the fatigue life under atmospheric [3,4]. It is necessary to perform fatigue tests for tubes
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