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직접 에너지 적층을 통한 STS316L 소재의 보수 공정에서 그루브 형상이 기계적 특성에 미치는 효과
오욱진,손용,손종윤,신광용,심도식 한국소성∙가공학회 2020 소성가공 : 한국소성가공학회지 Vol.29 No.2
This study explores the effects of different pre-machining conditions on the deposition characteristics and mechanical properties of austenitic stainless steel samples repaired using direct energy deposition (DED). In the DED repair process, defects such as pores and cracks can occur at the interface between the substrate and deposited material. In this study, we varied the shape of the pre-machined zone for repair in order to prevent cracks from occurring at the slope surface. After repairs by the DED process, macro-scale cracks were observed in samples that had been pre-machined with elliptic and trapezoidal grooves. In addition, it was not possible to completely prevent micro-crack generation on the sloped interfaces, even in the capsule-type grooved sample. From observation of the fracture surfaces, it was found that the cracks around the inclined interface were due to a lack of fusion between the substrate and the powder material, which led to low tensile properties. The specimen with the capsule-type groove provided the highest tensile strength and elongation (respective of 46% and 571% compared to the trapezoidal grooved specimen). However, the tensile properties were degraded compared to the non-repaired specimen (as-hot rolled material). The fracture characteristics of the repaired specimens were determined by the cracks at the sloped interfaces. These cracks grew and coalesced with each other to form macro-cracks, they then coalesced with other cracks and propagated to the substrate, causing final fracture
레이저로 적층 제조된 STS316L에 대한 직접에너지적층 응용 보수 시 공정 중 후열처리(In-Situ Post Heating) 효과
오욱진,손용,심도식 대한금속·재료학회 2019 대한금속·재료학회지 Vol.57 No.8
An explosively formed penetrator (EFP) is a kind of kinetic energy warhead that contains a metal linear structure. After exploding, the linear structure in the EFP is deformed and hits the target as a form of aero-stable long-rod penetrator. To achieve high penetration performance, Ta is commonly used as the linear material due to its high density and formability. In this study, we investigated changes in the shape and microstructure of the Ta linear after explosion, especially for two cases; flying just before impact, and after impact. The computational simulation revealed that the disc shaped linear structure was elongated in the flying direction after the explosion, which was consistent with the results of the experiment. As the microstructure of the Ta linear could be changed during flight and after penetrating the target, samples of each stage were prepared. Microstructure analysis showed that severe deformation and dynamic recrystallization occurred repeatedly during flight after explosion, which seemed due to the increased temperature that results from the friction between the linear and air. After penetrating the target, the shape of the Ta linear was severely changed and grain size was drastically increased. At the moment when the EFP hit the target, the sharp increase in temperature would exert a critical impact on grain growth.
오욱진,문혜신 한국임상심리학회 2002 Korean Journal of Clinical Psychology Vol.21 No.1
강박증에 대한 신경심리학적 연구들이 많이 이루어짐에 따라서 강박증이 다른 장애와는 구별되는 특정한 양상의 인지적 손상을 보이는 두뇌의 기능 장애라는 증거들이 증가하고 있는 추세이며, 최근에는 강박증 환자들의 인지적 손상이 전두엽 주변체계(frontal-striatal system)의 역기능과 관련된다는 가설이 제시됨으로서 강박증 환자들의 기억 손상과 함께 기억에 있어서의 전략적 측면, 조직화 능력의 손상에 대한 관심이 고조되고 있다. 본 연구에서는 먼저 강박증 환자의 언어적, 비언어적 기억 능력의 손상에 대해 살펴본 후, 이러한 기억 손상이 기억과정의 조직화 책략에서 기인하는지에 대한 매개가설을 검증하고자 하였다. 20명의 강박장애 환자와 20명의 정상 통제집단에게 RCFT, HVLT를 실시하였으며, RCFT에서의 조직화 전략을 평가하였다. 연구 결과, 강박증 환자 집단은 언어적 기억 능력과 비언어적 기억 능력 모두에서 유의미한 손상을 나타내었지만, 언어적 기억 능력에서의 손상은 보다 부분적으로 나타났다. 회귀분석 결과, 강박증 환자의 비언어적 기억 능력의 손상은 조직화 전략의 손상에 의해 직접적인 영향을 받는 것으로 나타났지만, 집단 차이와 기억 손상간의 직접적인 경로 또한 유의미한 것으로 나타나고 있어서 강박증 환자의 기억 손상에는 조직화 전략이 중요한 영향을 미치기는 하지만, 이외에도 다른 인지적 결손이나 특징과 관련될 가능성을 시사해주고 있다.
직접 에너지 적층 공정을 이용한 보수 공정에서 보수 폭에 따른 기계적 특성 관찰
오욱진(Wook-Jin Oh),신광용(Gwang-Yong Shin),손용(Yong Son),심도식(Do-Sik Shim) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.3
This study explores the effects of repair width on the deposition characteristics and mechanical properties of stainless steel samples repaired using direct energy deposition (DED). In the DED repair process, defects such as pores and cracks can occur at the interface between the substrate and deposited material. In this study, we changed the width of the pre-machined zone for repair in order to prevent cracks from occurring at the inclined surface. As a result of the experiment, cracks of 10–40 μm in length were formed along the inclined slope regardless of the repair width. Yield and tensile strength decreased slightly as the repair width increased, but the total and uniform elongation increased. This is due to the orientation of the crack. For specimens with a repair width of 20 mm, yield and tensile strength were 883 MPa and 1135 MPa, respectively. Total and uniform elongations were 14.3% and 8.2%, respectively. During observation of the fracture specimens, we noted that the fracture of the specimen with an 8 mm repair width occurred along the slope, whereas specimens with 14 mm and 20 mm repair depths fractured at the middle of the repaired region. In conclusion, we found that tensile properties were dependent upon the repair width and the inclination of the crack occurred at the interface.
오욱진(Oh, Uk-jin) 忠北大學校 中原文化硏究所 2012 중원문화연구 Vol.18·19 No.-
Through documents and archeological evidences, this thesis examines when Baekjae advanced to Jungwon. Jungwon was a key spot in where the ancient Three Kingdoms struggled against one another, and Baekjae occupied there for the first time among them. According to Samkuksagi, Jungwon was the center of the southern part of Baekjae where was the central target of conquest, after King Koi`s reign. The archeological evidences such as construction of fortresses and stylistic transitions of sepulchre specifically show the debouchment of Baekjae to Jungwon. After 4th century, the fortresses of Baekjae tended to swarm near Jungwon area, especially in Namhan River area, and Moho River area, and the eastern-southern part of Kyunggi. These evidences signify that Baekjae actively advanced to Jungwon than to other areas. The fact that the sepulchers of local clans like Mahan were dominantly constructed until 3rd to early 4th century, and the construction stopped since early 4th century is noteworthy characteristics of the sepulcher clusters in Jungwon. It can be understood that Baekjae aggressively advanced to Jungwon in early 4th century when Mahan`s sepulcher constitution declined, although the very first contact between them might had been earlier than that. Baekjae`s aggrandizement of its realm to Jungwon is noteworthy in its intensity, not only because it was geologically crucial, but also because iron, the strategically important resource of those days, could be attained in there.