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핵융합로용 저방사화 철강재료(JLF-1)의 강도와 파괴인성
윤한기(H.K.Yoon),김동현(D.H.Kim),이상필(S.P.Lee),박이현(Y.H.Park),공유식(Y.S.Kong),Y.Katoh,A.Kohyama 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
Reduced activation ferritic steel, JLF-1 steel (Fe-9Cr-2W-V-Ta), is one of the promising candidate<br/> materials for fusion reactor applications. Fracture toughness (JIC) and tensile tests were carried out at<br/> room temperature and elevated temperature (400 ℃). Two types of CT specimen were prepared to<br/> examine the effect of rolling direction on the fracture toughness of JLF-1 steel. Four types of tensile<br/> specimen were also prepared to investigate the property by the rolling direction and welding. The<br/> Micro Vickers hardness was measured at various distances of a cross section of the TIG joints of<br/> JLF-1 steel according to the heating history of each position. Finally, the fracture surface was observed<br/> by scanning electron microscopy (SEM).
ODS Ferritic / Martensitic 강의 고온강도 특성
윤한기(H. K. Yoon),A Kimura 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
Oxide dispersion strengthened(ODS) materials for structural application in fusion reactors world allow to increase the operating temperature to approximately 650℃. A micro-structural analysis and tensile test were performed on three ODS ferritic/martensitic steels between R.T. and 600℃. Dispersion hardening represents an interesting approach to improve the mechanical properties at elevated temperature, as they are foreseen in the future fusion reactor. Three ODS variants of the 10Cr-ODS(K1), 13Cr-Al-ODS(K2) and 19Cr-Al-ODS(K4) with Y₂O₃ content of 0.37wt% have been produced. The micro-structure of compacted material has been characterized by means of optical and electron microscope(SEM). It has been successfully demonstrated that it is possible to expan the temperature range for the application of fusion reactor.
핵융합로용 저 방사화 페라이트강(JLF-1)의 피로균열진전 거동
윤한기(H.K. Yoon),이상필(S.P. Lee),공유식(Y.S. Kong),김사웅(S.W. Kim),박원조(W.J. Park),A.Kohyama(A. Kohyama) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
The objective of this study is to investigate fatigue life and fatigue crack propagation behavior in the Reduced Activation Ferritic Steel (RAFs) JLF-I. The experiment of fatigue life for JLF-I steel have been carried out for the stress ratio R=0 at room temperature. The fatigue crack propagation behavior of the JLF-I steel was investigated by the constant-amplitude loading test for the stress ratios R=0.1, 0.3 and 0.5 respectively. The effects of stress ratios and specimen size on the fatigue crack growth behaviors for JLF-I steel were discussed within the Paris law. At room temperature, the fatigue limits of longitudinal and transverse direction to the rolling direction were 470 MPa and 490 MPa at 1X 10_7<br/> cycles. respectively. The base material of JLF-I steel showed the isotropic behavior in fatigue properties of the rolling direction and the test temperature. The fatigue crack propagation rate of a half size specimen was similar to that of a full size specimen at the stress ratios of 0.1, 0.3 and 0.5 respectively. The fatigue crack propagation behavior of this material was evaluated by using a half size specimen.
박경동(K. D. PARK),김정호(J. H. KIM),윤한기(H. K. Yoon),박원조(W. J. PARK) 한국해양공학회 2001 韓國海洋工學會誌 Vol.15 No.2
Elastic-plastic fracture toughness JIC can be used as an effective design criterion in elastic plastic fracture mechanics. Most of these systems are operated at high temperature and JIC values are affected by temperatuere. therefore, the JIC value at high temperature must be determined for use of integrity evaluation and designing of such systems. Elastic-plastic fracture toughness JIC tests were performed on SA516/70 carbon steel plate and test results were analyzed according to ASTM E 813-87, ASTM E 813-89 and ASTM E 1152-87. Safety and integrity are required for reactor pressure vessels because, they are operated in high temperature. there are single specimen method, which used as evaluation of safety and integrity for reactor pressure vessels. In this study, elastic-plastic fracture toughness(JIC) and J-△a of SA 516/70 steel used as reactor pressure vessel steel are measured and evaluated at room temperature, 150℃, 250℃ and 370℃ according to unloading compliance method.
原子爐用 低合金鋼의 高溫疲勞크랙傳播 特性 및 破壞인성에 관한 硏究
朴卿東(K. D. Park),吳世旭(S. W. Oh),尹漢基(H. K. Yoon) 한국해양공학회 1989 韓國海洋工學會誌 Vol.3 No.1
Fatigue crack growth characteristics and crack closure for an A 508-3 steel were investigated at elevated temperatures(100, 150, 288, and 350℃). The results obtained are summarized as follows ;<br/> 1) While the relation of fatigue crack growth rate da/dN and stress intensity factor range ΔK, is appeared in the linear straight line over the range of da/dN> 5×10<SUP>-9</SUP> m/cycle at 25℃.<br/> That the low fatigue crack propagation rate, experimentically, is appeared at more high temperature region than 25℃.<br/> The crack growth rate da/dN is also increased with increased stress ratios.<br/> 2) Threshold ΔKth is found to be dependent on fretting oxide induced crack closure at 25℃, fretting oxide and oxide scale induced crack closure at 100 crack closure at 288~350℃.<br/> And that the occurrence of fretting oxide induced closure and oxide scale induced crack closure is depended on stress ratios.<br/> 3) The occurrence of oxidation of crack surface that elevated temperature can affect the formation of fretting oxide debris in fatigue crack growth and has an important role on the near-threshold characteristics.<br/> 4) It can be possible to exclude the contrbution due to fretting oxide debris and oxidation at elevated temperature on the near-threshold characteristics by the selection of moderate test temperature.<br/> In this case, the characteristics are controlled only by plasticity induced crack closure and become a structure and environment insensitive material corstant.
압력용기용 SA516/70 강의 고온피로균열 진전거동에 대한 연구
박경동(K. D. PARK),김정호(J. H. KIM),윤한기(H. K. YOON),박원조(W. J. PARK) 한국해양공학회 2001 韓國海洋工學會誌 Vol.15 No.2
The fatigue crack propagation behavior of the SA516/70 steel which is used for pressure vessels was examined experimentally at room temperature, 150℃, 250℃ and 370℃ with stress ratio of R=0.1 and 0.3. The fatigue crack propagation rate da/dN related with the stress intensity factor range △K was influenced by the stress ratio within the stable growth of fatigue crack(Region Ⅱ) with an increase in △K. The resistance to the fatigue crack growth at high temperature is higher in comparison with that at room temperature, and the resistance attributed to the extent of plasticity-induced by compressive residual stress according to the cyclic loads. Fractographic examinations reveal that the differences of the fatigue crack growth characteristics between room and high temperatures are mainly explained by the crack closure and oxide-induced by high temperature.