摘要(英) |
High-cycle, low-cycle fatigue tests and fatigue crack propagation measurements were conducted on SA533B1 steels, reactor pressure vessel (RPV) steels, with four levels of sulfur content (0.0062 wt%~ 0.035 wt%) at room temperature and 300 ℃. Efforts were made to study the effects of sulfur content on the fatigue degradation of RPV steels. Fractographic and microstructural examinations by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were performed to investigate the fatigue crack initiation and propagation mechanism. To make a comparison of different crack measurement techniques, fatigue crack length measurements were concurrently taken on the same specimen by an alternating current potential drop technique and a crack opening displcement gauge. Fatigue crack opening levels were also measured to characterize the fatigue crack closure effect on fatigue crack growth behavior.
The results of high-cycle fatigue (HCF) limit were observed to be ~650 MPa, around the yield strength of SA533B1 steel, and showed little or no dependence on sulfur content at room temperature. At 300℃, the fatigue limits were slightly higher than those tested at room temperature, notably for the steel with a sulfur content 0.006 wt% whose fatigue limit at 300℃ was up to 702 MPa. The low-cycle fatigue (LCF) limit showed little or no dependence on sulfur content, but significantly depended on the test temperature. Fatigue life could be predicted either by means of the strain-life equation or the SWT (Smith, Watson, and Topper) parameter for specimens under low-cycle fatigue conditions. The strain-life equation for SA533B1 steel in air was irrespective of the sulfur content, but dependent on the test temperature. HCF life was significantly affected by the inclusions which are composed of O, Al, S, Ca, and Mn. The inclusions were randomly distributed on the surface or in the interior of the specimen. Fractographic examination results suggested that inclusions near the specimen surface served as the crack initiation site for a majority of the fatigued specimens tested at room temperature. For those tested at 300℃, some cracks were identified to initiate around the inclusions in the interior of the fatigued specimens. However, the effects of inclusion on the LCF are less significant than HCF. No LCF specimens were observed to initiate at/around the inclusions.
The fatigue resistance of SA533B1 steel subjected to HCF and LCF tests at 300℃ was improved by the combined effects of dynamic strain aging (DSA) and grain size reduction. DSA and grain size reduction increase the steel strength, accordingly improve the HCF and LCF limits at 300℃. But, concurrently, the precipitation of carbides/nitrides in SA533B1 steel leads to a decrease in the steel strength. The grain size reduction and the precipitation compete with each other. The grain size reduction is dominant and the net effect is reflected in an increase in hardness value.
The crack growth rate measurements for steels of different sulfur contents tested at room temperature and 300℃ can be characterized by the same material constants C = 1.98*10-8 and m = 2.54 for Paris law, where da/dN is in mm/cycle and ?K in MPa . It implies that fatigue crack growth rate has little or no dependence on sulfur content and test temperatures (25℃, 150℃ and 300℃). But fatigue crack growth rate becomes faster, when crack propagation runs parallel to the sulfide orientation. Fatigue crack closure became evident till the stress ratio (R value) was decreased to the values smaller than 0.13. Thus, for the tests at the stress ratio of R = 0.2, it is not necessary to calibrate the ?K value. The results of crack opening measurement show that the levels of crack closure significantly depend on the loading history and plastic zone size ahead of crack tip. The phenomenon of crack closure was observed to be more significant for the specimens with a through crack than those with a surface crack.
Smaller subgrains and a greater number of precipitates were identified with the specimens tested at 300?C by SEM and TEM examinations. No clear relationship was found between fatigue damage and the mis-orientation changes of cell walls (or subgrain boundaries) in the fatigued samples of SA533B1 steel. |
參考文獻 |
(A)期刊論文
1. P. K. Liaw, H. Wang, L. Jiang, B. Yang, J. Y. Huang, R. C. Kuo, and J. G. Huang, “Thermography Detection of Fatigue Damage of Pressure Vessel Steels at 1,000 Hz and 20 Hz”, Scripta Materialia, Vol. 42, 2000, pp. 389-395.
2. J. Y. Huang, R. Z. Li, K. F. Chien, R. C. Kuo, P. K. Liaw, B. Yang, and J. G. Huang, “Fatigue Behavior of SA533-B1 Steels”, ASTM Fatigue and Fracture Mechanics: 32nd Volume, STP 1406, 2001, pp.105-121.
3. B. Yang, P. K. Liaw, H. Wang, L. Jiang, J. Y. Huang, R. C. Kuo, and J. G. Huang, “Thermography Investigation of the Fatigue Behavior of Reactor Pressure Vessel (RPV) Steels”, Materials Science and Engineering, A314, 2001, pp. 131-139.
4. C. Y. Chen, J. Y. Huang, J. J. Yeh, R. C. Kuo, J. R. Hwang and J. G. Huang, “Microstructural Evaluation of Fatigue Damage in SA533-B1 and Type 316L Stainless Steels”, Journal of Materials Science. Vol. 38, 2003, pp. 817-822.
5. J. Y. Huang, J. R. Hwang, J. J. Yeh, C. Y. Chen, and R. C. Kuo, “On the Low Cycle Fatigue Resistance of SA533 Steels” Materials Science and Technology, in press.
6. J. Y. Huang, J. R. Hwang, J. J. Yeh, C. Y. Chen, R. C. Kuo, and J. G. Huang, “Dynamic Strain Aging and Grain Size Reduction Effects on the Fatigue Resistance of SA533 Steels” Journal of Nuclear Materials, in revision.
7. 黃俊源,李仁志,簡艮夆,郭榮卿等,“反應爐壓力槽鋼材疲勞壽限評估”,核研季刊, 第36期, 第34-45頁,民國89年7月。
8. 李後龍,葉基榮,黃俊源,“SS316L不銹鋼高週疲勞及音洩量測研究”,檢測科技,第十九卷,第三期,第84-90頁,民國90年5-6月。
9. 黃俊源,葉基榮,簡艮夆,郭榮卿等,“反應爐壓力槽鋼材疲勞行為偵測與評估”,台電工程月刊, 第639期, 第78-96頁, 民國90年11月。
10. 葉基榮,黃俊源,宋游楠崑,郭榮卿等,"SS316L不銹鋼在高溫高壓水媒中之低週疲勞行為”,防蝕工程季刊發表中
(B)研討會論文
1. J. Y. Huang, C. Y. Chen, K. F. Chien, R. C. Kuo, L. Jiang, B. Yang, H. Wang, P. K. Liaw, and J. G. Huang, “High-cycle Fatigue Behavior of SA533-B1 Steels”, American Society for Testing and Materials (ASTM), 31st National Symposium on Fatigue and Fracture Mechanics, Cleveland, Ohio, June 21-24, 1999.
2. J. Y. Huang, C. Y. Chen, K. F. Chien, R. C. Kuo, P. K. Liaw, and J. G. Huang, “Fatigue Behavior of Reactor Pressure Vessel Steels”, Julia Weertman Symposium, The Minerals, Metals, and Materials Society (TMS), Y. W. Chung, D. Dunand, P. K. Liaw and G. Olson, eds., Fall Meeting, October 31-November 4, 1999, pp. 373-384.
3. R. Z. Li, J. Y. Huang, J. J. Yeh, R. C. Kuo, et al., “ Life Prediction of Reactor Pressure Vessels under Cyclic Loading”, Prof. Campbell Laird Symposium, The TMS Annual Meeting, Nashville, TN, March 13-16, 2000.
4. B. Yang, P. K. Liaw, H. Wang, L. Jiang, J. Y. Huang, R. C. Kuo, and J. G. Huang, “Temperature Evolution and Fatigue Damage of Reactor Pressure Vessel (RPV) Steels”, TMS Meeting, 184 Thorn Hill Road, Warrendale, PA 15086-7514, pp. 25-36, 2000.
5. H. L. Lee, J. Y. Huang, J. J. Yeh, “High-Cycle Fatigue Cracking Behaviors of Low Alloy Steel SA533B1 and Type 316L Stainless Steel and Acoustic Emission Measurements”, 3rd International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurized Components, Seville, Spain, Nov. 14-16, 2001.
6. J. J. Yeh, J. Y. Huang, R. C. Kuo, “High-cycle fatigue behavior of type 316L Stainless Steel”, International Symposium on Experimental Mechanics (ISEM), Taipei Grand Hotel, Taiwan, Dec. 28~30, 2002.
7. 李後龍, 黃俊源, “SA533B1鋼材高週疲勞行為與音射量測研究”, 第七屆破壞科學研討會,墾丁福華飯店,民國91年3月 22-23日。
8. 黃俊源, 葉基榮, 陳長盈,郭榮卿,黃振國等, "動態應變時效和晶粒細化效應對SA533鋼材高週疲勞行為研究”, 90台電/核究所委託合作研發成果研討會, 91年6月14日, 核究所。
9. 黃俊仁,馮君平,許育銓,黃俊源,”反應器壓力槽疲勞壽限評估模式之研究” 第十一屆國防科技研討會,中正理工學院,民國91年7月25日。
10. 葉基榮,黃俊源,宋游楠崑,郭榮卿等,"SS316L不銹鋼在高溫高壓水媒中之低週疲勞行為”,防蝕工程學會,民國91年8月22日~23日,台中東勢林場。
11. 黃俊仁,陳奎澧,馮君平,黃俊源,郭榮卿等,“SA533B1壓力槽鋼材之疲勞裂縫閉合與裂縫成長研究”, 第十九屆機械工程研討會, 民國91年11月29日~30日。
(C)其他
1. 台電/核研所核能發電廠技術發展專業”反應爐壓力槽鋼材疲勞行為偵測與評估第一次進度報告”,民國87年9月。
2. 台電/核研所核能發電廠技術發展專業”反應爐壓力槽鋼材疲勞行為偵測與評估第一次期中報告”,民國88年3月。
3. 台電/核研所核能發電廠技術發展專業”反應爐壓力槽鋼材疲勞行為偵測與評估第二次進度報告”,民國88年9月。
4. 台電/核研所核能發電廠技術發展專業”反應爐壓力槽鋼材疲勞行為偵測與評估第二次期中報告”,民國89年3月。
5. 台電/核研所核能發電廠技術發展專業”反應爐壓力槽鋼材疲勞行為偵測與評估第三次進度報告”,民國89年9月。
6. 台電/核研所核能發電廠技術發展專業”反應爐壓力槽鋼材疲勞行為偵測與評估期末報告”,民國90年3月。
7. 葉基榮,黃俊源,郭榮卿,“316L不銹鋼高週疲勞特性研究”, INER-T2492,民國87年12月。
8. 葉基榮,黃俊源,郭榮卿,“SS316L不銹鋼組件鋼材及SA533B1壓力槽鋼材疲勞行為與壽限評估研究”, INER-T2697, 民國90年2月。
9. 黃俊源,簡艮夆,郭榮卿等," SA533B1壓力槽鋼材疲勞行為研究”,INER-2066,民國90年10月。
10. 陳仁宏,黃俊源,陳國衍,俞君俠,簡艮夆,廖文珍,黃俊雄,徐鴻發,“核四廠一號機反應爐第一層基座焊道267龜裂肇因分析報告” INER-T2910,民國91年11月。
11. 陳國衍,黃俊源,葉基榮,郭榮卿,“SA533B1壓力槽鋼材受循環負載裂縫成長與壽限評估之數值分析研究”,INER-T2941,民國92年1月。 |