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계기용 밸브 재질의 검증 인장시험에 의한 사용적합성 평가
신인환(In Hwan Shin),박치용(Chi Yong Park) 한국압력기기공학회 2021 한국압력기기공학회 논문집 Vol.17 No.1
In this paper, an application example for fitness-for-service of material is shown. A kind of instrument valve is made of austenitic stainless steel fabricated by the cold working process. The tensile strength of the cold worked austenitic stainless steel has to be limited under 90 ksi to prevent the stress corrosion cracking in power plants. In industrial fields, tensile strengths of some materials were discovered to be over the regulation requirements in a certified material test report (CMTR). Owner’s verification tests were performed to compare with that in a CMTR and to check the appropriateness. It is found that, in the case of verification test under the required test speed, valve materials could be used in the field. Although it is only one application sample of material check process in the power generation site, this case study could show an importance of basic experimental technology in academia and research circles.
신인환(Shin In-Hwan),강현구(Kang hun-Gu),이선동(Lee Sun-Dong),유호천(Yoo Ho-Chun) 한국태양에너지학회 2010 한국태양에너지학회 학술대회논문집 Vol.2010 No.11
Energy conservation and greenhouse gas reduction have been increasingly important amidst climate change. This study thus is intended to evaluate the energy-saving effect by natural cooling. For indoor space, the temperature requiring cooling was estimated at 26℃ as a result of simulation using typical meteorological year weather data. It's aimed at achieving cooling effect by inducing natural ventilation during the time when ambient temperature is 24℃ or below. Inducing the air outside also improved the indoor air quality by increasing the ventilation. Given the air inside bus was relatively inferior among the various indoor environments while it's structurally easy to induce the air outside, analysis of energy conservation effect by cooling load was conducted inside express bus. When a bus runs at 100㎞/h, the velocity of airflow coming through the vent was 1.65m/s on average with the ventilation of 4,716㎥/h.
맞대기 용접부가 존재하는 SA312 Tp304L 배관의 4점 굽힘시험을 통한 J-R 선도 평가
신인환(In Hwan Shin),이경수(Kyoung Soo Lee),석창성(Chang Sung Seok) 대한기계학회 2018 大韓機械學會論文集A Vol.42 No.11
본 연구에서는 시험편의 보수성을 정량적으로 평가하기 위하여 맞대기 용접된 오스테나이트계 스테인리스강(SA312 Tp304L) 배관을 대상으로 표준시험편을 이용한 파괴인성시험과 배관의 4점 굽힘시험을 수행하고 J-R 선도를 비교하였다. 우선 4점 굽힘시험 결과로부터 맞대기 용접부에서의 최대하중 지지능력이 모재와 유사함을 알 수 있었으며, 실제 배관의 J-R 선도에 비해 낮게 평가된 표준시험편으로 구한 용접부의 J-R 선도를 배관의 LBB 평가에 직접 적용하는 것은 매우 보수적임을 알 수 있었다. 따라서 배관의 LBB 안전여유도를 정확히 평가하기 위해서는 모재와 용접부의 인장물성과 파괴인성 뿐만 아니라 실제 배관의 파괴특성을 모두 포함한 추가적인 안전여유도의 평가 또한 고려되어야 할 것이다. In this study, fracture toughness tests using standard specimens proposed in the ASTM E1820, and 4-point bending tests using austenitic stainless steel pipes with butt-welding joints are performed to quantitatively estimate specimen conservation. First, the maximum load-carrying capacity of a butt welding joint is similar to that of the substrate of a pipe considering the results of 4-point bending tests. In addition, it is very conservative to determine the leak-before-break (LBB) safety margin of a pipe using the standard specimen directly because the value of the J-R curve obtained for the butt-welding joint using the specimen is smaller than that of the J-R curve for the actual pipe. Therefore, the estimation of an additional safety margin should be considered to determine accurately the LBB safety margin of a pipe considering not only the tensile properties and fracture toughness for both the base metal and butt-welding joint of the pipe but also fracture characteristics of the actual pipe.
한계하중법을 이용한 Curved CT 시험편의 파괴저항곡선에 미치는 형상변수 영향 평가
신인환(In Hwan Shin),박치용(Chi Yong Park),석창성(Chang Sung Seok),구재민(Jae Mean Koo) 대한기계학회 2014 大韓機械學會論文集A Vol.38 No.7
본 연구에서는 한계하중법을 이용하여 Curved CT 시험편의 J-적분에 미치는 형상변수 영향을 평가하였다. 주요 형상변수인 시험편의 길이와 폭의 비(L/W), 평균곡률반경과 두께의 비(Rm/t)에 대한 파괴인성시험 후, ASTM 시험법에서 제시한 표준시험편의 J-적분과 한계하중법으로 구한 J-적분을 각각 적용하여 구한 파괴저항곡선을 평가하였다. 또한 배관의 파괴저항곡선을 잘 모사한다고 알려진 휨 광폭평판(CWP) 및 표준시험편의 파괴저항곡선과 비교? 고찰하여 최종적으로 Curved CT 시험편의 파괴저항곡선에 대한 유효성을 평가하였다. 본 논문의 결과는 향후 실배관의 정확한 파괴인성을 평가하는 데 있어 Curved CT 시험편의 적용가능성을 평가하는 데에 활용할 수 있다. In this study, the effect of shape parameters on the J-R curves of curved CT specimens was evaluated using the limit load method. Fracture toughness tests considering the shape factors L/W and Rm/t of the specimens were also performed. Thereafter, the J-R curves of the curved CT specimens were compared using the J-integral equation proposed in the ASTM (American Society for Testing and Materials) and limit load solution. The J-R curves of the curved CT specimens were also compared with those of the CWP (curved wide plate), which is regarded to be similar to real pipe and standard specimens. Finally, the effectiveness of the J-R curve of each curved CT specimen was evaluated. The results of this study can be used for assessing the applicability of curved CT specimens in the accurate evaluation of the fracture toughness of real pipes.
오스테나이트계 스테인리스강 용접재(ER347)의 파괴인성에 미치는 열화 영향 평가
신인환(In Hwan Shin),이호중(Ho Jung Lee),박상규(Sang Kyu Park) 대한기계학회 2019 大韓機械學會論文集A Vol.43 No.3
본 연구에서는 ER347 용접재의 파괴인성에 미치는 열화 영향을 평가하기 위하여 GTAW 방식으로 덧살올림 용접한 블록에 대한 인장 및 파괴인성시험을 수행하였다. 열화 후 ER347 용접부의 강도가 열화 전에 비해 약 10 % 증가하였으나 5,000 시간 이후에는 강도 변화가 둔화되었다. 그러나 파괴인성은 열화시간에 반비례하여 꾸준히 감소하였다. 시험결과를 토대로 볼 때 ER347 용접재의 열화 영향을 정확히 평가하기 위해서는 강도 뿐 만 아니라 파괴인성도 함께 고려해야 할 것으로 보인다. 또한 ER347 용접재의 파괴인성이 주조스테인리스강, E308 및 ER316 용접재에 비해 상대적으로 높게 나타났는데 이에 대한 원인은 델타-페라이트의 함량, Nb 성분으로 보이며 이에 관한 후속 연구를 수행할 예정이다. In this study, we evaluated the thermal aging effect of ER347 welds by performing tensile and fracture toughness tests for welding blocks made by GTAW and the build-up welding method. The strength of the aged welds increased by approximately 10% compared to that of the as-welded status, and the variation in strength slowed after 5,000 hours. However, the fracture toughness of welds decreased gradually in inverse proportion over time. The test results suggest that fracture toughness, as well as strength, should be considered to accurately evaluate the thermal aging effect. Furthermore, the fracture toughness of ER347 welds was determined to be higher than that of cast stainless steel, E308 and ER316 welds. This may be occurring due to the δ-ferrite contents and Nb component. A follow-up study will be conducted on this issue.
신인환(Shin In-Hwan),유호천(Yoo Ho-Chun) 한국태양에너지학회 2011 한국태양에너지학회 학술대회논문집 Vol.2011 No.4
This paper deals with the free cooling system of express bus using natural energy source in order to improve the room air quality and save cooling energy. In an express bus, there are may passengers in unit area, requiring the improvement of air quality and giving higher energy saving efficiency. Particularly, the express buses running fast make it easy to take in outdoor air at a flow rate controllable with a damper mechanism. This paper proposes the analysis on the air flow achieved by a damper controlled vertically and horizontally in order not to deteriorate the ride comfort of the passengers