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용접입열량에 따른 CO₂용접부의 기계적 특성에 관한 연구
국정한,성호현 한국기술교육대학교 2001 論文集 Vol.8 No.1
ABSTRACT In this study, we investigate the welding characteristics, mechanical properties, stress intensity, fracture strength, and microstructure in the fusion zone of SS400 steels which were welded at four different heat inputs(10, 15, 20, and 25 KJ/cm) using either the flux cored wire (FCW) or solid wire (SW) in the CO2 welding system. Based on arc's stability, spatter, thinned-slag detachment, and bead apperance results, the mechanical properties of the FCW were much better than those of the SW. They decreased as heat increased. The increase of heat input and notch depth result in a decrease of the impact energy.
국정한,성호현,장복수,김남훈 한국기술교육대학교 2003 論文集 Vol.10 No.1
In this study, welding characteristic and mechanical properties of electro slag welding were systematically studied for SM490A and TMCP steel.In the electro slag welding which is widely used SM490A and TMCP steel materials are mainly used in a steel structures and complex building. As SM80G, ZO60 and SM70G are usually used welding wire. In this study, mechanical properties such as tensile strength, elongation and impact energy were measured for each welding conditions to determine the optimum processing conditions. In addition, hardness and microstructural analysis were conducted to characterize the welding properties. There results indicate that TMCP is suitable base material and SM80G, and ZO60 are the good welding electrodes for the electro slag welding.
안정 크랙 성장에 있어서의 표준 Duplex강의 파괴거동
국정한 한국기술교육대학교 1994 論文集 Vol.1 No.1
In this study, the fracture behavior of standard duplex steel(UR45N) heat-treated at 1050℃ for 60min. and at 850℃ for 30min. was investigated. The fracture behavior of duplex steel using the SENB specimens was determined by J integral and CTOD tests. The results obtained in this study can be summarized as follows. 1. The Stretch Zone Widths(SZW, W=30mm) measured by scanning electron micrographs were 25㎛ (850℃) and 125㎛(1050℃), which were close to Ji values corresponding the crack incremental (da) in the onset of crack propagation. It was also discussed the possibility of the determining variable for the extent of brittle and ductile fracture by fractography. 2. Based on the J integral and CTOD test results, there was little change in the Jo.2 value with changing the specimen width in the onset of crack propagation. In cases where the test specimen heat-treated at 1050℃ for 60min. exhibited a lower width change than that at 850℃ for 30min. Since Ji, Jo.2 and CTOD values were useful fracture parameters in the elastic-plastic fracture, it was found that there was a proportional relationship between Ji and CTOD(di). 3. Specimens heat-treated at 1050℃ for 60min. showed a fibrous fracture surface, whereas specimens heat-treated at 850℃ for 30min. exhibited cleavage and fibrous fracture surface.
냉각수 유속 변화에 따른 고주파 용접기용 가변 리엑터 / 커패시터의 변형에 관한 연구
국정한(Kook, Jeong-Han),박광진(Park, Gwang-Jin),김기선(Kim Key-Sun) 한국산학기술학회 2011 한국산학기술학회논문지 Vol.12 No.10
본 논문에서는 고주파 용접기의 가변 리엑터 및 커패시터를 해석하여 최적화 설계 하였다. 고주파 용접기의 극판 부분은 콘덴서의 역할을 하기 때문에 큰 정전 용량의 콘덴서를 만들기 위해서는 유전율이 큰 재료의 선택과 극 판의 면적을 크게 하고, 극판의 간격을 얇게 하여야 한다. 하지만 많은 전류가 흐르기 때문에 저항이 발생하여 열이 발생하게 된다. 이러한 극판의 열 변형을 막기 위하여 냉각수 등을 이용한 방법으로 극판의 열을 식힌다. 이때 극판 의 변형 및 온도에 따른 냉각수의 속도를 최적화 하였다. In this paper, variable reactor and capacitor for high-frequency welder are analyzed by optimum design. As the polar panel of high-frequency welder has the role of condenser, the material with the high rate of induced electricity has to be selected in order to manufacture the condenser with the great power cut. And the area of polar panel must be large and the gap between panels must be thin. On the contrary, the resistance is generated and the heat is happened because the large current is flown. To prevent the thermal deformation of this polar panel, the temperature can be lowered by using cooling water and so on. At this point, the speed of cooling water due to deformation and temperature of polar panel can be optimized.
국정아 한국중앙영어영문학회 2008 영어영문학연구 Vol.50 No.3
This article suggests that T-to-C movement occurs in a main-wh interrogative even when the subject is a wh-phrase. When the subject wh-phrase in Spec-TP moves to Spec-CP, suppression of agreement on C is assumed to occur, which is also found in languages like Turkish and Palauan, though in different ways. In this case the trace of T is visible to affix hopping. When the object wh-phrase moves to Spec-CP, the suppression of agreement on C does not occur, which makes do-insertion applicable. Therefore, the contrast between subject and nonsubject asymmetry with respect to do-insertion follows.