• Journal of the Korean Society for Advanced Composite Structures
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• v.5 no.1
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• pp.28-36
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• 2014

This study describes the development of innovative connections between steel beams and concrete-filled tube columns that utilize a combination of low-carbon steel and super-elastic shape memory alloy components. The intent is to combine the recentering behavior provided by the shape memory alloys to reduce building damage and residual drift after a major earthquake with the excellent energy dissipation of the low-carbon steel. The analysis and design of structures requires that simple yet accurate models for the connection behavior be developed. The development of a simplified 2D spring connection model for cyclic loads from advanced 3D FE monotonic studies is described. The implementation of those models into non-linear frame analyses indicates hat the recentering systems will provide substantial benefits for smaller earthquakes and superior performance to all-welded moment frames for large earthquakes.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1889-1893
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• 2008

본 연구에서는 완경사 계단형 낙차공에서 하류수심 변화에 따른 도수 형태의 변화와 WTF 흐름 특성에 대한 분석을 수행하였다. 일정한 유량에서 하류수위를 증가시키면 도수 형태가 달라지는데 특히 계단 끝단에서 완전도수, 잠김도수(B점프), downward curved jet, upward curved jet, wave type flow(WTF)가 차례로 나타났다. 잠김도수에서는 표면 롤러 현상이 관찰되었고 curved jet에서는 큰 유속 감세 없이 파가 하류까지 전달되었다. WTF에서는 사류흐름이 바닥 recirculation 구역의 영향으로 변형되면서 wave 형태의 도수를 발생시켰다. 하류수위를 점점 증가 시키면 도수의 발생 위치가 계단 위쪽으로 이동하며 잠김도수와 WTF가 번갈아가며 발생하였다. 하류수위가 높아질수록 도수의 규모는 작아졌으며 표면 롤러도 미약해지는 경향을 보였다. 세 가지 유량조건에 따른 WTF의 규모를 비교한 결과 유량이 증가할수록 WTF의 크기가 증가하였으며 무차원화한 WTF의 형상은 거의 비슷한 것으로 나타났다. 계단형 낙차공은 기존낙차공에서 발생하는 도수와 달리 WTF가 발생되므로 이에 대한 분석이 필요하다. WTF가 발생하는 구간의 수위는 하류수위보다 높아지기 때문에 하천 설계 시 하천 접합부의 조건(구수부지설치, 제방설치 등)에 따라 wave의 높이가 설계의 중요 인자로 고려되어야 할 것이다. WTF는 지금까지의 계단형 낙차공 설계 시 고려되지 못한 부분으로서 차후에 계단형 구조물 또는 계단식 변형 구조물 설계 시 주요 자료로 활용 될 것이다.

• The Journal of Korean Institute for Practical Engineering Education
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• v.3 no.1
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• pp.45-50
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• 2011

Despite the highly sophisticated development of finite element analysis, a finite element model for structural dynamic analysis can be inaccurate or even incorrect due to the difficulties of correct modelling, uncertainties on the finite element input data and geometrical oversimplification, while the modal data extracted from measurement are supposed to be correct, even though incomplete. The assumption that the test results represent the true dynamic behaviour of the structure, however, may not be correct because of various measurement errors. The measurement errors are investigated and their effects on estimated frequency response functions(FRFs) are also investigated.

• Journal of Korean Association for Spatial Structures
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• v.6 no.1 s.19
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• pp.75-82
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• 2006

The single layer latticed dome is very sensitive on the slenderness ratio and half open angle of the elements, load condition, and the connection type because it is organized by a lot of thin elements, so we have to use the geometrically nonlinear buckling load when the buckling of the structures is analyzed. But, it is very difficult to design the single layer latticed domes considered all renditions. Therefore the purpose of this paper is to propose the appropriate design method of the single layer latticed dome considered the geometrically nonlinear buckling load in base of the linear buckling load by the eigenvalue analysis.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.1
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• pp.73-80
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• 2005

Injection molding is the most widely used process for the industrial forming of plastic articles. During an injection molding process of composites, the fiber-matrix separation and fiber orientation are caused by the flow of molten polymer/fiber mixture. As a result, the product tends to be nonhomogeneous and anisotropic. Hence, it is very important to clarify the relations between separation orientation and injection molding conditions. So far, there is no research on the measurement of fiber orientation using image processing. In this study, the effects of fiber content ratio and molding condition on the fiber orientation-angle distributions are studied experimentally. Using the image processing method, the fiber orientation distribution of welding parts in injection-molded products is assessed. And the effects of fiber content and injection mold shapes on the fiber orientation in case of fiber reinforced polymeric composites are studied experimentally.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.9
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• pp.829-836
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• 2009

3-Dimensional flow which is represented by horseshoe vortex is generated as a type of secondary flow about the main flow. As well, it causes the flow loss. The present study deals with the leading edge fence shape on a wing-body junction to decrease a horseshoe vortex, one of the main factors to generate the secondary flow losses. The shape of leading-edge fence was optimized with the design variables of the installed height, length, width, and thickness of the fence as the design variables. Approximate optimization design method is used as the optimization. The study was investigated using $FLUENT^{TM}$ and $iSIGHT^{TM}$. Total pressure coefficient of the optimized design case was decreased about 7.5 % compare to the baseline case.

• Journal of Welding and Joining
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• v.19 no.1
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• pp.49-57
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• 2001

In this study, the residual stress fields of multi-pass welded were analyzed by FEA under various geometrical conditions. In order to estimate the effects of pipe geometries on residual stress distribution, welding processes of each model were performed under the same heat cycles. And then, the influence of cutting off the weld bead on the residual stress redistribution was also estimated. From the results, in the range of t/D=0.05, axial residual stresses on the outer surface of the welded pipe were linearly decreased with pipe diameter increase. On the other hand, hoop residual stresses were not influenced by them. And both axial and hoop residual stresses on the outer surface of the welded pipe were increased with pipe diameter increase. But, when t/D was smaller than 0.05, they were converged in the nearly same value. The maximum residual stresses were generated at around HAZ. It in therefore necessary to consider them in welding design, strength evaluation, and analysis of fracture characteristics.

• Korean Journal of Materials Research
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• v.10 no.8
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• pp.532-539
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• 2000

Co-0.5C-(15~20)Cr-20Ni-8W-(2~7)Fe alloy bond in diamond-impregnated abrasive tool was synthesized by ball-milling and mechanical alloying process. When the powders were mechanical alloyed for 6h, micro-welding in most metal powders was observed irrespective of addition of stearic acid. Without stearic acid in metal powders, partial-ly coarse powders were obtained, which could be unfaverable to the densification of composite of composite powders. The hot-pressed compacts showed rupture strength of 1100MPa and hardness of about $46H_{RC}$, respectively.

• Journal of Welding and Joining
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• v.17 no.6
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• pp.53-61
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• 1999

The use of thick plate in increasing in recent years due to the rapid expansion of chemical plants, nuclear plants, ships and other industrial plants. Welding is the most popular joining techniques employed in manufacturing industrial machineries and structures. Normally, Groove shapes are prepared according to appropriate rules and regulations such as KS, JIS, AWS, LR, DNV and etc. for various thicknesses of plate. However those groove angles tend to be too large. As a result of large groove angle, residual stress, deformation of material and strength reduction is obtained. Therefore, the reliability and safety of structures and machinery tend to be decreasing. Therefore, in this paper, theoretical as well as experimental study are carried out to find optimum groove shapes for T-welded joint of mild steel. The test specimen are made in same condition with simulation model. Welding residual stresses measurement by sectional cutting method. ⅰ) The mechanical difference for change the thickness of plate and groove angle are not appeared. ⅱ) In a mechanical point of view minimum preparation angle(40°) is more suitable than maximum groove angle(60℃). ⅲ) The measurement value and distribution of welding residual stresses are not effected largely by groove angle. It is mechanical restraint that mainly affect welding residual stresses distribution. In mechanical point of view minimum groove angle is more suitable than maximum groove angle. Therefore, it is appropriate to minimize the size of groove shape in strength and safety.

• Journal of Welding and Joining
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• v.29 no.4
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• pp.67-72
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• 2011

The proportion of the welding in the production process of machinery, buildings and marine structures is increasing and the joining are mainly conducted by butt and fillet weld. In the case of fillet weld, the shape of structures is complicated depending on the constraint on the geometry of the structures, therefore, the full penetration is mostly difficult. Accordingly, it is necessary to establish safe and economical criteria of design of the structures through the strength based on the penetration state of the fillet weld. Patterns of fatigue failure in cruciform fillet weld jont appear in the form of the root, toe and mixed failure. In the case of toe and mixed failure, the fatigue strength is higher than root failure. Therefore, we have to make the enough depth of penetration or perform the welding work through improving the fatigue strength of cruciform joints in welded structures. So it is necessary to optimize the penetrated depth in the range of the possible mixed failure and find the way in the cost-effective design to lessen the amount of the welding work.