• Journal of Convergence for Information Technology
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• v.9 no.7
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• pp.94-99
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• 2019

Friction stir welding was first reported by TWI(The Welding Institute) in 1991, and this welding method has been rapidly used in various industrial areas such railway, automobile, aerospace and shipbuilding industry. Here, we study core characteristics of friction stir welding (FSW) applied to Al 6005-T6 extruded sheets, which is the typical alloy used for railway car bodies. With the fixed welding speed of 500 mm/min, the rotating tool speed was varied from 600 to 1800 RPM. The results of hardness measurement revealed that the hardness of nugget area is ~70% with respect to the parent material, and for the selected range of rotation speed, no clear dependence was observed and the hardness values close to the parent materials were achieved for the area located 5 mm away from the welding interface. The tension test shows that yield strength and tensile strength were slightly decreased with increasing RPM, with no observed difference for the elongation.

• The Journal of the Korean bone and joint tumor society
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• v.15 no.2
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• pp.93-103
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• 2009

Purpose: We evaluated the outcomes of surgical reconstructions using recycled autograft augmented with VFG for bone defects caused by tumor resections. Materials and Methods: Ten patients with a malignant or locally aggressive bone tumor who were managed with recycled autograft augmented with VFG and followed up minimum 1 year were evaluated for bone union, functional result and complications. The influence of various factors on bone union and functional outcomes were also analyzed. Results: Bone unions were obtained at 13 of 20 junctions. Average union time was 3.7 months at metaphyseal junctions and 8 months at diaphyseal junctions (P<0.05). At diaphyseal junctions, younger aged group and intramedullary location group showed earlier bone union (P<0.05). The mean functional score was 81%. There were 3 nonunions, 4 delayed unions and 2 recycled bone resorption combined with fractures. Conclusion: To obtain excellent results, proper microvascular technique, sufficient length of VFG bridging both junctions, stable internal fixation and protection of reconstructed bone until union are necessary.

• Journal of Korean Society of Steel Construction
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• v.22 no.6
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• pp.533-541
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• 2010

H-shaped beams, which are constructed between columns, are used widely as slaves in steel structures. The bending moments that occur on both ends of an H-shaped beam, however, are about twice the bending moment that occurs at the center of the H-shaped beam. Because such beam is designed with maximum bending moment, it is deeper and has smaller spaces. To improve these features, if both ends of an H-shaped beam that have maximum bending moments are merely reinforced, the beams could be designed by the bending moment at the center of the H-shaped beam. To analyze the structural performance of the proposed end-reinforced beams (eco-girders). Four specimens were prepared with the following parameters: end-reinforced steel plate, reinforced bars, and reinforced studs and experimental tests of the specimens were performed.

• Journal of Korean Society of Steel Construction
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• v.21 no.5
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• pp.527-536
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• 2009

The purpose of this experimental study was to investigate the block shear fracture behavior and curling effect on a single shear-bolted connection in thin-walled carbon steel fabricated with four bolts. The specimens that fail by block shear were planned to have a constant dimension of the edge distance perpendicular to the loading direction, bolt diameter, pitch, and gage. The main variables of the specimens were plate thickness and end distance parallel to the loading direction. A monotonic tensile test was carried out for the bolted connections, and the ultimate behaviors, such as the fracture shape, ultimate strength, and curling, were compared with those that had been predicted using the current design specifications. The conditions of curling occurrence in terms of plate thickness and end distance were also investigated, and the strength reduction due to curling was considered.

• Conservation Science in Museum
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• v.9
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• pp.1-15
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• 2008

We observed the section and microstructure by Scanning Electron Mirrorscope (SEM) for 4 'Bowls, white porcelain with impressed floral design and sliver bound rim' and 1 'Dish, white porcelain with sliver bound rim', which was manufactured by reverse firing and metal bound rim was wrapped to the part of not being spread glaze at inlet, in Jingdezhen white porcelains, the relics dug from the seabed of Shinan conserved in National Museum of Korea, and found that the ingredient of metal rim was not silver but tin as a result of measuring by BEI of Energy Dispersive Spectroscopy (EDS). And as a result of survey with Fourier transform infrared spectroscopy(FT-IR) for checking the method of joining metal rim of mouth part, it was found that joining was made with materials made of lacquer.

• Journal of Bio-Environment Control
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• v.27 no.4
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• pp.391-399
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• 2018

In this paper, experimental study performed on steel-pipe connections for structural members of a greenhouse is presented. By those experiments performed, bending moment, deformation and stress distribution of specimens were investigated under four point bending test. The bending performance according to connection method using pin and the stretching is also investigated. The results of bending performance of the no connection specimen were compared to those of other connection specimens. The pin and stretching connection specimens showed lower banding performance than the no connection specimen. The stretching connection method was relatively higher bending performance than the pin connection specimens. According to the results, we proposed the connection method with good bending performance that can be applied to steel-pipe connection in greenhouse.

• Journal of Welding and Joining
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• v.11 no.3
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• pp.10-21
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• 1993

용접공정에 시각센서를 도입하여 고정 오차, 용접물 준비 상태에 상관없이 유연성을 확보할 수 있고 용접부 형상에 따라 용접 변수를 조절하는 적응제어가 가능하다. 본 해설에서는 용접 자동 화에 이용되는 시각센서의 원리를 설명하였고 상업화되어 쓰이고 있는 시각센서들을 소개하였다. 시각센서를 용접 공정에 적용하기 위해 센서의 신뢰도 향상, 센서와 로봇간의 정보 교환, 용접환 경으로부터 센서의 보호기술등의 개발이 요구됨을 알 수 있었다. 지난 10여년간 용접자동화에 기 계시각을 도입하고자 하는 연구가 활발히 진행되어 자동차, 항공기, 원자력 발전 설비 등의 생산 현장에서 시각센서의 우수성이 입증되고 있다. 현재 접촉식 센서나 아크센서에 비해 가격이 높은 단점이 있어 상업화에 어려움이 있으나 필요 부품들의 계속적인 가격 하락으로 점차 시각센서의 이용이 증대될 것이다. 특히, 아크센서로는 추적할 수 없는 박판 용접과 레이저 용접등의 정밀 용 접공정에서 수요가 커질 것으로 예상된다.

• Journal of Korean Society of Steel Construction
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• v.25 no.5
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• pp.463-474
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• 2013

Many experimental and numerical researches for thin-walled carbon steel and austenitic stainless steel single shear bolted connections have been conducted and the modified design equations of ultimate strength were proposed. In this study, the tests of double shear bolted connections with bolt arrangements ($2{\times}1$, $2{\times}2$) and end distance parallel to the loading direction as main variables were performed. Specimens were planed with a constant dimension of edge distance perpendicular to the loading direction, bolt diameter, pitch and gauge like single shear bolted connections. The test results such as ultimate strength and fracture mode were compared with those of current design standards. Furthermore, modified block shear equations for double shear bolted connections were suggested.

• Journal of Korean Society of Steel Construction
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• v.18 no.6
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• pp.717-726
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• 2006

Traditional external post-tensioning method using either steel bars or tendons is commonly used as a retrofitting method for steel composite bridges. However, the method has some disadvantages such as stress concentration at anchorages and inefficient load-carrying capability of live loads. Multi-stepwise prestressing method using thermal expanded coverplate is a newly proposed prestressing method, which was originally developed for prestressing steel structures. A new retrofitting method for steel girder bridges founded on a simple concept of thermal expansion and contraction of cover plate, the method is a hybrid of and combines the advantages of external post-tensioning and thermal prestressing. In this paper, basic concepts of the method are presented and an illustrative experiment is introduced. From actual experimental data, the thermal prestressing effect was substantiated and the FEM approach for its analysis was verified. The retrofitting effects ofa single-span bridge were analyzed and the feasibility of the developed method was examined.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.441-448
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• 2014

From several researches, recently, it was found that using hollowed precast concrete (HPC) column made more compact concrete casting in joint region possible than using normal solid PC (Precast concrete) column. Therefore, the rigidity of joints can be improved like those of monolithic reinforced concrete (RC). After filling the hollow with grout concrete, however, it is expected that the HPC column behaviors like composite structure since PC element and grout concrete have different materials as well as there is a contact surface between two elements. These may affect the structural behavior and strength of the composite column. A compressive strength test was performed for the HPC column with parameter of hollow ratio for the case with and without grout in the hollow and the result is presented in this paper. The hollow ratios in the test are 35, 50 and 59% of whole section of column. Concentrated axial force was applied to top of the specimens supported as pin connection for both ends. In addition, finite element (FE) analysis was performed to simulate the failure behavior of HPC column for axial compression. As a result, it was found that the hollow ratio did not affect the initial stiffness of HPC filled with grout regardless of the strength difference of HPC and grout. However the strength was increased inversely corresponding to the hollow ratio. The structural capacity of HPC without grout closely related to the hollow size. Especially, the local collapse governs the overall failure when the thickness of HPC is too thin. Based on these effect, a suitable equation was suggested for calculation of the compressive strength of HPC column with or without grout. FE analysis considering the contact surface between HPC and grout produced a good result matched to the test result.