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우완측,김동규,안규백,Woo, Wanchuck,Kim, Dong-Kyu,An, Gyu-Baek 대한용접접합학회 2015 대한용접·접합학회지 Vol.33 No.1
Residual stresses are inherently introduced into the engineering components during manufacturing including rolling, forging, bending and welding processes. Excessive residual stresses are known to be detrimental to the proper integrity and performance of components. Neutron diffraction has become a well-established technique for the determination of residual stresses in welds. The deep penetration capability of neutrons into most metallic materials makes neutron diffraction a powerful tool for the residual stress measurements through the thickness of the weld specimen. Furthermore, the unique volume-averaged bulk characteristic of the scattering beam and mapping capability in three dimensions is suitable for the engineering purpose. In this presentation, the neutron diffraction measurements of the residual stresses will be introduced and measurement results will highlighted in thick weld plates.
굴곡측정법을 이용한 극후판 용접부 잔류응력분포 정량분석
김동규,우완측,강윤희,Kim, Dong-Kyu,Woo, Wanchuck,Kang, Youn-Hee 대한용접접합학회 2015 대한용접·접합학회지 Vol.33 No.1
Residual stresses arising from the materials processing such as welding and joining affect significantly the structural integrity depending on the external loading condition. The quantitative measurement of the residual stresses is of great importance in order to characterize the effects of the residual stresses on the structural safety. In this paper, we introduce a newly devised destructive technique, the contour method (CM), which is applied for the measurements of the residual stress distributions through the thickness of a 80 mm thick steel weld. Residual stresses are evaluated from the contour, which is the normal displacement on a cut surface produced by the relaxation of residual stresses, using a finite element model. The CM provides a two-dimensional map of the residual stresses normal to the cut surface. The CM developed in the present study was validated in comparison with the residual stress distribution determined by a well-established neutron-diffraction residual stress instrument (RSI) instrumented in HANARO neutron research reactor.
서석호,우완측,이수열,Seo, Sukho,Huang, E-Wen,Woo, Wanchuck,Lee, Soo Yeol 한국재료학회 2018 한국재료학회지 Vol.28 No.7
Fatigue crack growth retardation of 304 L stainless steel is studied using a neutron diffraction method. Three orthogonal strain components(crack growth, crack opening, and through-thickness direction) are measured in the vicinity of the crack tip along the crack propagation direction. The residual strain profiles (1) at the mid-thickness and (2) at the 1.5 mm away from the mid-thickness of the compact tension(CT) specimen are compared. Residual lattice strains at the 1.5 mm location are slightly higher than at the mid-thickness. The CT specimen is deformed in situ under applied loads, thereby providing evolution of the internal stress fields around the crack tip. A tensile overload results in an increased magnitude of the compressive residual stress field. In the crack growth retardation, it is found that the stresses are dispersed in the crack-wake region, where the highest compressive residual stresses are measured. Our neutron diffraction mapping results reveal that the dominant mechanism is by interrupting the transfer of stress concentration at the crack tip.
고유변형도법에 의한 두께 25mm 맞대기용접부의 두께방향의 잔류응력측정
박정웅,안규백,우완측,허승민,Park, Jeong-Ung,An, Gyu-Baek,Woo, Wanchuck,Heo, Seung-Min 대한용접접합학회 2013 대한용접·접합학회지 Vol.31 No.4
Overlay welding is carried out to improve the corrosion resistance, wear resistance and heat resistance on the surface of the chemical plant and steelmaking plant structures. In overlay welding, control of the bead size and the temperature distribution of weldment are particularly important because that is directly connected to the improvement of quality and productivity. The aim of this study is to model the welding heat source that is very useful to analyze the bead size and temperature distribution of weldment. To find the welding heat source model, numerical analyses are performed by using FE software MSC-marc.
안규백,배홍열,노병두,안영호,최종교,우완측,박정웅,An, Gyubaek,Bae, Hong-Yeol,Noh, Byung-Doo,An, Young-Ho,Choi, Jong-Kyo,Woo, Wanchuck,Park, Jeong-Ung 대한용접접합학회 2015 대한용접·접합학회지 Vol.33 No.1
Recently, there have been the increase of ship size and the development of oil and gas in arctic region. These trends have led to the requirements such as high strength, good toughness at low temperature and good weldability for prevent of brittle fracture at service temperature. There has been the key issue of crack arrestability in large size structure such as container ship. In this report for the first time, crack arrest toughness of thick steel plate welds was evaluated by large scale ESSO test for estimate of brittle crack arrestability in thick steel plate. For large structures using thick steel plates, fracture toughness of welded joint is an important factor to obtain structural integrity. In general, there are two kinds of design concepts based on fracture toughness: crack initiation and crack arrest. So far, when steel structures such as buildings, bridges and ships were manufactured using thick steel plates (max. 80~100mm in thickness), they had to be designed in order to avoid crack initiation, especially in welded joint. However, crack arrest design has been considered as a second line of defense and applied to limited industries like pipelines and nuclear power plants. Although welded joint is the weakest part to brittle fracture, there are few results to investigate crack arrest toughness of welded joint. In this study, brittle crack arrest designs were developed for hatch side coaming of large container ships using arrest weld, hole, and insert technology.