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소듐, 리튬금속화재에 대한 불활성 기체 소화약제의 적용성 분석
최명락(Myung Rak Choi),이건석(Lee, Geonseok),이승현(Seung Hyun Lee) 한국위험물학회 2020 한국위험물학회지 Vol.8 No.2
This study aims to assess the application of an inert gas fire extinguishing agent for extinguishing metal fire. Sodium and lithium were used as the metallic combustibles. Testing was executed by altering the oxygen concentrations in the order of 21, 6, 4 % by using inert gas fire extinguishing agents including IG-01, IG-541, and IG-100. Since metal features risks of dispersion and explosion, fire was generated by after having adjusted the inert gas extinguishing agent concentration in advance. Regarding the test results, The lower the oxygen concentration, explosion occurred without the manifestation of sparks or a flame. In addition, it was possible to obtain the same results for all of the fire extinguishing agents, namely, IG-541, IG-100, and IG-01. Through this test, it was possible to confirm the characteristics of metal fire and the applicability of IG-01, IG-541, and IG-100 to metal fire. Although it was confirmed that IG-541, unlike the results of NFPA 12 and NFPA 2001, can be applied to metal fire, it is deemed to be the result of the difference in the testing conditions.
소듐금속화재에 대한 아르곤 가스 소화약제의 적용성 분석
최명락(Myung Rak Choi),이승현(Seung Hyun Lee) 한국위험물학회 2020 한국위험물학회지 Vol.8 No.1
This study aims to assess the application of an argon fire extinguishing agent for extinguishing sodium metal fire. For this purpose, a chamber for the exclusive use of sodium metal fire (1 ㎥) was produced for this study and tests were conducted with argon fire extinguishing agent by varying the argon gas extinguishing agent concentrations in the order of 100, 80.9, 71.4, 57, 47.5, 0 %. Since sodium metal features risks of dispersion and explosion, fire was generated by after having adjusted the argon gas extinguishing agent concentration in advance. Regarding the test results, a flame was observed continuously and fire broke out along with the explosion of sodium when the argon gas extinguishing agent concentration was 0 %, along with continuous occurrences of explosions and scattering. When the argon gas extinguishing agent concentration was 47.5 %, the size of the flame was reduced by about 80 %, while there was no manifestation of the flame although explosions and sparks of sodium were generated when the argon gas extinguishing agent concentration was 71.4 %. When the argon gas extinguishing agent concentration is 80.9 %, explosion occurred without the manifestation of sparks or a flame. It was possible to confirm the characteristics of sodium metal fire through this test and that the argon gas extinguishing agent can be applied to sodium metal fire.
원전 구조재료의 반복 변형거동에 미치는 경년열화 영향 평가
최명락(Myung Rak Choi),김진원(Jin Weon Kim) 대한기계학회 2018 大韓機械學會論文集A Vol.42 No.3
본 논문에서는 원전 구조재료의 반복 변형거동에 미치는 경년열화 영향을 파악하기 위해서, 반복 응력-변형률 시험을 수행하였다. 시험에는 각각 원전 운전환경에서 40년 동안 열취화와 중성자 조사취화된 재료를 모사한 400℃에서 4,292시간 가속열화된 CF8A 주조 스테인리스강과 33 % 냉간가공 TP316L 스테인리스강이 사용되었다. 시험 결과, CF8A 주조 스테인리스강의 응력-변형률 이력곡선, 반복경화/연화 거동, 그리고 반복 응력-변형률 거동에 미치는 열취화의 영향은 크지 않았다. 그러나, 냉간가공된 TP316L 스테인리스강의 응력-변형률 이력곡선, 반복경화/연화 거동, 그리고 반복 응력-변형률 곡선은 냉간가공 전과 비교하여 크게 변화되었다. 따라서, TP316L 스테인리스강의 반복 변형거동에 미치는 조사취화의 영향은 뚜렷한 것으로 예측된다. This study conducted the cyclic stress-strain test to investigate the effect of aging degradation on the cyclic deformation behavior of nuclear structural materials. In the experiment, CF8A cast austenitic stainless steel (CASS) thermally aged at 400 °C for 4,292 h, and 33 % cold-worked (CW) TP316L stainless steel (SS) were employed as materials to simulate, respectively, thermal aging and irradiation embrittlement occurring during a 40 y operating period of nuclear power plants. The results indicate that the effect of thermal aging on the cyclic deformation behavior of CF8A CASS is insignificant. However, it is seen that cold-working considerably alters the cyclic deformation behavior of TP316L SS. Thus, it is expected that the effect of irradiation embrittlement on the cyclic deformation behavior of TP316L SS is apparent.
LBB 평가를 위한 J-R 파괴인성시험 결과에 미치는 시편 형상과 측면 홈의 영향
김진원(Jin Weon Kim),최명락(Myung Rak Choi),오영진(Young Jin Oh),박흥배(Heung Bae Park),김경수(Kyung Su Kim) 대한기계학회 2015 大韓機械學會論文集A Vol.39 No.7
본 논문에서는 파단전누설 평가를 위한 J-R 파괴인성시험에 미치는 시편 크기와 측면 홈의 영향을 분석하였다. 이를 위해서 SA508 Gr.1a 배관재에서 채취된 측면 홈이 가공되거나 가공되지 않은 크기가 다른 3종류의 CT 시편(12.7mm 두께의 1T-CT, 25.4mm 두께의 1T-CT, 25.4mm 두께의 2T-CT)을 이용하여 상온과 316oC에서 J-R 시험을 수행하였다. 시험 결과, 시편 두께에 관계없이 측면 홈이 가공된 시편은 측면 홈이 없는 시편에 비해 낮은 J-R 곡선을 보였으며, 상온에 비해 316oC에서 측면 홈의 영향이 더욱 뚜렷하였다. 상온에서는 시편의 두께가 감소하고 폭이 증가함에 따라 J-R 곡선이 약간씩 감소하는 경향을 보였으나, 316oC에서는 시편의 두께가 감소하고 폭이 증가됨에 따라 J-R 곡선이 증가하였다. 그러나 SA508 Gr.1a 배관재에서 전체적으로 시편의 폭과 두께에 따른 J-R 곡선의 변화는 크지 않았다. In this study, the effects of specimen size and side-groove on the results of the J-R test for leak-before-break (LBB) evaluation were investigated. A series of J-R tests were conducted at both RT and 316oC, using three different sizes of compact tension (CT) specimens machined from SA508 Gr.1a piping material: 12.7 mm-thick 1T-CT, 25.4 mm-thick 1T-CT, and 25.4 mm-thick 2T-CT with and without side-groove. The results showed that side-grooving reduced the J-R curve for all specimens and the effect of side-grooving was more significant at 316oC than at RT. As the thickness of the specimens decreased and the width of the specimens increased, the J-R curve slightly decreased at RT but it increased at 316oC. However, the variation in the J-R curve of SA508 Gr.1a with the thickness and width of CT specimen was insignificant.
상온과 316℃에서 SA508 Gr.1a 저합금강 배관과 TP316 스테인리스강 배관의 변형거동에 미치는 하중속도의 영향
김진원(Jin Weon Kim),최명락(Myung Rak Choi) 대한기계학회 2015 大韓機械學會論文集A Vol.39 No.4
본 논문에서는 원전 배관 재료의 변형거동에 미치는 하중속도의 영향을 파악하기 위해서, SA508 Gr.1a 저합금강과 SA312 TP316 스테인리스강 배관재를 대상으로 상온과 원전 운전온도인 316℃에서 다양한 변형률 속도로 인장시험을 수행하였다. 시험 결과, 상온에서는 두 배관재의 변형거동이 일반적인 하중속도 의존성을 보였다. 즉, 하중속도가 증가함에 따라 강도는 증가하고 연성은 감소하는 경향을 보였다. 그러나, 316℃에서는 하중속도가 증가함에 따라 SA508 Gr.1a 저합금강의 강도와 연신률이 모두 감소하였고 단면수축률은 감소 후 증가하는 비선형 거동을 보였다. SA312 TP316 스테인리스강의 강도, 연신률, 그리고 단면수축률은 하중속도에 관계없이 거의 일정한 값을 보였다. 시험 온도에 관계없이 SA508 Gr.1a 저합금강의 가공경화능력은 하중속도에 거의 영향을 받지 않았으나, SA312 TP316 스테인리스강에서는 하중속도가 증가함에 따라 가공경화능력이 감소하였다. This study conducted tensile tests on SA508 Gr.1a low alloy steel and SA312 TP316 stainless steel piping materials under various strain rates at room temperature (RT) and 316°C to investigate the effects of loading rate on the deformation behavior of nuclear piping materials. At RT, the deformation behavior for both pipe materials showed a typical loading rate dependence, i.e., the strength increased and the ductility decreased as the loading rate increased. At 316°C, however, the strength and elongation of SA508 Gr.1a low alloy steel decreased as the loading rate increased, and its reduction of area non-linearly varied with the loading rate. For SA312 TP316 stainless steel, the strength, elongation, and reduction of area at 316°C were almost the same regardless of the loading rate. At both temperatures, the strain hardening capacity was nearly independent of the loading rate for SA508 Gr.1a low alloy steel, while it decreased with increasing loading rate for SA312 TP316 stainless steel.
LBB 평가를 위한 J-R 파괴인성시험 결과에 미치는 시편 형상과 측면 홈의 영향
김진원(Jin Weon Kim),최명락(Myung Rak Choi),오영진(Young Jin Oh),박흥배(Heung Bae Park),김경수(Kyung Su Kim) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
This study performed to investigate the effect of specimen size and side-groove on the results of J-R test for leak-before-break (LBB) evaluation. For this purpose, a series of J-R tests were conducted at RT and 316oC using three different sizes of compact tension (CT) specimens, 12.7mm thick 1T CT, 25.4mm thick 1T CT, and 25.4mm thick 2T CT, with and without side-groove. The specimens were machined from SA508 Gr.1a piping material. The results showed that J-R curves tested from CT specimens with side-groove were nearly independent of specimen size, although they slightly increased with decreasing thickness. However, J-R curves tested from CT specimens without side-groove were dependent on specimen thickness. Regardless of test temperature and specimen size, side-grooving reduced J-R curve.