• Journal of Korean Society of Steel Construction
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• v.27 no.5
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• pp.447-454
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• 2015

The researches on circular hollow section(CHS) connections have been conducted continuously because of development of material properties and complex local behavior of the connections. The purpose of this study is that the effects of material strength and chord wall slenderness on chord plastification and strength of CHS X-joint truss connection under compression on branch member were evaluated. To this end, finite element analyses were performed for various connections, using ANSYS Mechanical APDL program. Based on the analysis results, the design strength of the connections according to chord plastification limit state in KBC were examined. Finally, special considerations for CHS X-joint connection design were suggested.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.6
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• pp.778-783
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• 2015

We studied about the strength characteristics of the FRP bonding method due to reduce accident on the oceans and protect life for my people. We test tension and bending strength of butt joint, lap joint, V-scarf joint, X-scarf joint. The result of test, it's pattern is similar both tension and bending strength. Tension strength and bending strength was excellent in order to X-scarf-butt joint-V-scarf-lap joint. The tension strength is the best properties X-scarf showed a 57% strength rate of the basic material, and bending strength showed a 77% strength rate of the basic material. Overall, the X-scarf 12t joint has most excellent properties of tension and bending strength. The lap joint has worst properties of tension and bending strength. We have to test having different over-lay of V-scarf and X-scarf joint each 12t, 16t, 20t. V-scarf of 20t over-lay has excellent character of tension and bending strength. But X-scarf of 12t over-lay has excellent character of tension and bending strength. The results are shown to the contrary. The ship is received a lot of stress. it's hard to compare a direction both actual and test. But we can acknowledge material basic characteristic of strength through tension and bending test. We give the four repair method; butt joint, lap joint, V-scarf joint, X-scarf joint and the reduced ratio in comparison with basic material; In addition give the separated data for V-scarf and X-scarf characteristic of 12t, 16t, 20t overlay length. For our study repair man can select good repair method in his work station.

• Journal of Welding and Joining
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• v.3 no.2
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• pp.64-73
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• 1985

X선응력측정법은 결정의 각자간 거리를 표점으로 하는 각자변형도를 X선회절현상을 이용하여 직접규정하여 응력을 구하는 것이다. 따라서 비교재의 교정곡선으로 부터 간접적으로 응력을 측 정하는 자기법이나 초음파법 등의 비파괴측정법에 비하여 X 선응력측정법은 잔류응력과 같은 내부응력의 비파괴측정법에 알맞고 지금까지 많은 연구자에 의하여 용접부에 적용시키기 위한 시도가 행해졌었다. 앞서 말한 국제회의에서도 X선응력측정법을 취급한 논문이 6편이고 그 가운 데서 3편이 용접구조물 또는 이음부에 이 방법을 적용한 것이다. 그래서 본고에서는 먼저 용접 잔류응력의 발생기구와 계산법, 측정법에 대하여 기술하겠다. 똔 잔류응력이 용접이음부의 파괴 강도 및 용접균열에 미치는 영향, 용접잔류응력의 대책과 이용법에 대하여 일본에서의 연구를 중심으로 소개하겠다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1179-1185
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• 2011

Cold and hot-rolled carbon steel sheets are commonly used in railroad cars or commercial vehicles such as the automobile. The sheets used in these applications are mainly fabricated by spot welding, which is a type of electric resistance welding. However, the fatigue strength of a spot-welded joint is lower than that of the base metal because of high stress concentration at the nugget edge of the spot-welded part. In particular, the fatigue strength of the joint is influenced by not only geometrical and mechanical factors but also the welding conditions for the spot-welded joint. Therefore, there is a need for establishing a reasonable criterion for a long-life design for spot-welded structures. In this thesis, ${\Delta}P-N_f$ relation curves have been used to determine a long-life fatigue-design criterion for thin-sheet structures. However, as these curves vary under the influence of welding conditions, mechanical conditions, geometrical factors, etc. It is very difficult to systematically determine a fatigue-design criterion on the basis of these curves. Therefore, in order to eliminate such problems, the welding residual stresses generated during welding and the stress distributions around the weld generated by external forces were numerically and experimentally analyzed on the basis of the results, reassessed fatigue strength of gas welded joints.

• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.3
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• pp.290-297
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• 2024

In this study, the gas permeability characteristics according to the construction joint were evaluated under pressure conditions ranging from 0 to 300 psi. The pore distribution and pore ratio were analyzed using X-ray CT. The average porosity of the OPC specimen was 0.74 %, while the FA specimen showed a relatively low pore ratio of 0.51 to 0.65 % regardless of the presence of the construction joint. For the OPC and FA plain specimens with a thickness of 50 mm without construction joints, no gas permeation occurred below 300 psi. At 300 psi, the gas permeation rates of the specimens with rough and smooth construction joint surfaces were 0.28 L/min and 0.31 L/min, respectively, which were 1.7 times higher than those of the specimens without construction joints. This is because the construction joints affected the distribution of the pores and coarse aggregates and the penetration path within the concrete. The porosity in the construction joint was the highest at about 2 %, and it was confirmed that the pore ratio gradually increased as it approached the joint.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1859-1860
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• 2008

본 연구에서는 여러 대의 저해상도 프로젝터 영상을 결합하여 인간의 시야각을 채울 수 있는 하나의 고해상도 영상처럼 보이게 만드는 타일드 디스플레이(tiled display) 기법을 활용하여 가상 현실 기반 몰입형 시스템을 제작한다. 제안된 시스템은 총 8대의 프로젝터를 이용해 4096 x 1536의 고해상도 화면을 구현하며 유효 해상도는 3200 x 1200을 구현하였다. 각 프로젝터 출력 영상간의 연결 이음매가 두드러지지 않는 심리스(seamless) 기법을 활용해 관찰자의 높은 몰입감을 획득할 수 있었다. 제안된 시스템에서는 반도체 CMOS 공정을 가상 현실 공간에 구현하여 다수의 학습자들에게 기존의 정적인 이미지로 전달되던 반도체 제조 공정을 보다 효율적으로 학습하도록 돕고 있다. 구성된 시스템은 일반 개인용 PC 시스템 한 대로 구현이 가능하여 상대적으로 저렴한 가격으로 시스템을 구성할 수 있어 가상 현실 기반 몰입형 기술 교육 시스템의 대중화에 기여할 것으로 기대된다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.3
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• pp.265-275
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• 2005

The objective of this paper is to numerically assess the behavior of tubular X-joints with an internal ing stiffener, and to evaluate the reinforcement effect of a ring stiffener, and to establish the strength formulae. Nonlinear finite element analysis is used to compute the static strength of axially loaded tubular joints. Numerical and experimental results are in good agreement for tubular X-joints. The chord lengths of simple and ring-stiffened X-joints are suggested to reduce chord end effect. And, internal ring stiffener is found to be efficient In improving static strength of tubular X-joints. Maximum strength ratios are calculated as $1.5\sim3.5$. Regression analyses are performed considering practical size of ring stiffener and strength estimation formulae for tubular X-joints with an internal ring stiffener are proposed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.2
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• pp.225-234
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• 2001

This paper represents the vector fields, three dimensional mean velocities, the turbulent intensities, the turbulent kinetic energy, and the Reynolds shear stresses in the X-Y plane of gas swirl burner with a cone type baffle plate measured by using X-probe from hot-wire anemometer system. This experiment is carried out at flow rates 350 and 450ℓ/min respectively, which are equivalent to the combustion air flow rate necessary for heat release 15,000 kcal/hr in gas furnace, in the test section of subsonic wind tunnel. The vector plot shows that the maximum axial mean velocity component exists in the narrow slits situated radially on the edge of gas swirl burner, for that reason, there is some entrainment phenomena of ambient air in the outer region of burner. Moreover, mean velocities in the initial region are largely distributed near the outer region of burner at Y/R≒0.97, but they diffuse and develop into the center flow region of burner according to the increase of axial distance. The turbulent intensities and the turbulent kinetic energy due to large inclination of mean velocity and swirl effect show that the maximum value in the initial region of burner is formed in the narrow slits situated radially on the edge of gas swirl burner and large values are mainly formed in the entire region of burner after X/R=2.4358, hence, the combustion reaction is anticipated to occur actively near this region. And the Reynolds shear stresses are also largely distributed from slite to vanes of gas swirl burner in the intial region, but their values largely disappear after X/R=3.2052.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.41.2-41.2
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• 2009

최근 자동차 시장에서는 레이저 열처리에 대한 관심이 집중되고 있다. 이는 현재까지 사용되어 왔던 점용접에 비해 이음부 형상에 제한이 적고 자유도가 높으며 짧은 시간내에 용접을 마쳐 열변형의 문제가 적기 때문이다. 이러한 이점 때문에 자동차 시장의 기술개발 동향이 차체 부품의 경량화와 원가절감을 위한 신기술 개발로 레이저 가공 기술을 접목시키고 있으며 이러한 신공정 개발은 지속적으로 확대되어 가고 있는 추세이다. 본 실험에서는 차체 접합을 위하여 신기술로 대두 되고 있는 레이저 용접법으로 박판을 접합하였다. 실험 조건은 동일한 재료 두 판을 합쳐 전력량을 변화시켰으며, 전력량의 한 조건을 잡아 용접 속도에 변화를 주었다. 용접 샘플의 물성을 평가하기 위하여 제품 내부의 구조를 비파괴 시험법을 통하여 분석하여 내부적 결함 및 내부 구조를 관찰하고, 열영향부 및 용접부 내부의 조직을 관찰하여 신기술에 대해 재료적 물성을 평가하고자 한다. 평가방법은 산업용 단층 촬영기(CT X-RAY)를 이용하여 재료를 파괴하지 않고 용접상태에 따른 내부구조를 분석하였으며, 용접부, 열영향부 그리고 모재 부분에 대해 경도를 측정하여 용접조건에 따른 경도양상을 관찰하였다. 또한 부위별로 조직을 관찰하여 재료 내부의 상을 관찰하였다.

• Journal of Korean Society of Steel Construction
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• v.11 no.1 s.38
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• pp.43-54
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• 1999

The divergence connection between steel circular tubes is widely used in such structures as factory facilities, steel circular hollow section truss, and off-shore tower. Steel circular hollow section (SCHS) have close section, and it makes their per-unit production expense higher than open sectioned products like L-shape, H-shape steels, but the sectional resistance of SCHS against vertical compression and torsion is very high. Despite the structural merits of SCHS, however, many engineers dislike to use them in their design because of uncertainty regarding the stress distribution and deformation behavior at their connections. Therefore, this thesis dealt with X-type connections, the most common forms of connection, and studied their load-deformation relationship. It observed how to show the load-deformation relationship at steel circular tube connections according to the diameter-thickness ratio (D/T) of the chord and diameter of branch-diameter of chord ratio (d/D) and suggested prediction yield load using by ring analysis method.