• Journal of Korean Society of Steel Construction
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• v.16 no.5 s.72
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• pp.555-564
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• 2004

Steel materials, which are normally used in bridge structures, are prone to corrosion and have thin plate structures. Steel bridges that have been damaged through increased vehicle load and corrosion are frequently expected to be strengthened. Repair or strengthening methods generally include cutting, bolting, and welding. The basic characteristics of stress and deformation behavior generated by cutting and welding in the course of the repair work, however, are not yet understood. It is difficult to say whether the safety of the structure after welding conforms with existing safety evaluation methods.Therefore, to gain confidence in the material and to guarantee the safety of the structure after welding, the stress generated by heat, through welding and cutting, was generalized. The effect of additional loads with respect to stress generated by heat was also investigated.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.4
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• pp.365-374
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• 2004

Steel bridges, which have been damaged by load and corrosion, need repair or strengthening. That is a cause of decreasing the durability of structure. In order to solve these problems, welding repair and strengthening methods can be considered. In general, cutting and welding procedure is carried out during the repair welding. Therefore, the investigation of the behavior of residual stress and deformation generated by cutting and welding is very important for safety of structure. Residual stress and deformation produced by gas cutting and arc welding were analyzed using 2D and 3D thermal elasto-plastic FEM. According to the results, the magnitude of temperature was analyzed by 2D-FEM is smaller than that was analyzed using the 3D-FEM at the start and end edge of flange. And the magnitude and distribution of residual stress of perpendicular direction of the cutting line and welding line was analyzed by the 2D-FEM was similar to that was analyzed by 3D-FEM. Therefore, it is possible to predict cutting and welding residual stress by 2D and 3D FEM.

• Proceedings of the KWS Conference
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• 2003.11a
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• pp.36-38
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• 2003

In order to understand the basic knowledge on the model of heat source in hybrid welding, authors have conducted finite element analysis to calculate heat distribution using three heat source models of non-split type and split type(Volume, Volume-Volume, Volume-Surface). From the research result, we can confirm that Volume-Volume heat source of split type is suitable for the analysis of heat distribution.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.162-164
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• 2005

570MPa grade weldable steels were $CO_{2}$ welded with various heat input and interpass temperature using flux cored wires. Effects of heat input and interpass temperature on the strength and toughness of weld metal were investigated and interpreted in terms of microstructural change, recovery of alloying elements, and the amount of reheated weld metal.

• Journal of Welding and Joining
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• v.12 no.3
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• pp.18-25
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• 1994

최근 건축용 강구조물이 초대형화 및 초고층화됨에 따라 용접물량의 급증하고 있으나 3D 직종에 대한 회피현상으로 용접기능자의 감소 및 인건비의 급증 등으로 인하여 건축용 강 구조물 제작시 경쟁력이 갈수록 저하되고 있다. 이에 대한 자구책으로 강 구조물 제작업체에서는 생산 성을 한층 배가 시킬 수 잇는 용접시공 기술을 자체 개발하거나 외부로부터 도입하고 있다. 본 보에서는 당사를 비롯하여 여러 업체에서 최근 개발된 용접기술 특히 대전류 SAW 기법, SESNET 기법 등의 초대입열 용접기술, Metal cored wire나 TIME 기법에 의한 고능률 GMAW 기법 및 Robot 용접 등에 대하여 간략히 기술하였다. 이 용접기술들의 적용에는 대개 고가의 시설투자가 수반되나, 이는 생산성 증가에 따른 원가절감으로 충분히 상쇄될 수 있다. 그러나 상기된 용접기술들의 적용에 대한 성패는 용접장비의 특성, 용접조건의 확립, 모재의 특성 혹은 주변 자동화 기술 및 상호 종속적인 관계에 크게 의존된다. 따라서 가 강 구조물 제작업체에서는 세심한 주위환경 분석을 토대로 각 업체에 가장 합당한 용접기술을 선정 및 적용하여야 하겠다.

• Journal of Welding and Joining
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• v.14 no.6
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• pp.81-92
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• 1996

This study is to compare the weldability of Zircaloy-4 end cap of nuclear fuel pin using by GTA and Nd :YAG LB. The welding parameters which affect bead width and penetration depth have been investigated. The effect of joint geometry of end cap for GTAW and LBW has been studied and optimum conditions of Zircaloy-4 endcap welding have been found. Microstructures and microhardness of GTA and LB welded zones have been also compared.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.165-167
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• 2005

Compared with Inconel 625 (ERNiCrMo-3) weld, Nb-free Alloy 59 (ERNiCrMo-13) weld with 15% Mo showed much higher resistance to hot cracking. Especially in the condition of current 350A and 30CPM of welding speed, no crack was detected at Inconel 625 fillet weld. Furthermore, it was found that the strength of Alloy 59 is sensitive to welding heat input. Up to around 14kJ/cm of heat input, Alloy 59 showed 678N/$mm^{2}$ of ultimate strength and 466N/$mm^{2}$ of yield strength. However, as heat input increased above 14kJ/cm, Alloy 59 weld could not satisfy the weld strength required for European LNG tank.

• Journal of Welding and Joining
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• v.10 no.2
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• pp.32-42
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• 1992

A method of optimization of process parameters in Arc Welding has been discussed in this paper. The method of investigation is based on the numerical calculation of weld bead by a finite element method and non-linear optimization technique is applied to estimated the optimization process parameters from the numerical calculation. The common package program(ANSYS 4.4A) was used to obtain the process parameters for a thin plate arc welding (TIG, CO$_{2}$). The results on some test are satisfactory and the used method of this paper is a useful guide to the optimum welding condition.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.93-101
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• 1987

Residual stresses have remained around welding areas of a steel structure member after welding operation. The major causes to occur these residual stresses are the local heat due to a welding, the heat stresses due to a irregular and rapid cooling condition, the material and rigidity of a steel structure. Ultimatly, these residual stresses have been known to decrease a brittle fracture strength, a fatigue strength, a buckling strength, dynamic properties, and the corrosion resistance of the material. This paper deals with the residual stresses on a steel structure member through experimental studies. SWS 58 plates were welded by the method of X-groove type. These plates were layed on the heat treatment at four different temperatures; $350^{\circ}C$, $500^{\circ}C$, $650^{\circ}C$ and $800^{\circ}C$. The resulting residual Stresses were measured by hole drilling method, and the followings were obtained. The residual stresses on the vicinity of a welding point were relieved most effectively at the temperature of $650^{\circ}C$, and these stresses relieved completly when the ratio of a hole diamerter to a hole depth became unity. Hardness test shows that the higher value of hardness at the heat affected zone dropped to belower as the temperature went up from $350^{\circ}C$ to $800^{\circ}C$. The Welding input heats have not influenced the magnitude of residual stresses at the input heat range between above and below one forth than standard.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.4
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• pp.738-746
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• 1988

Fatigue crack propagation of duplex stainless steel weldments was studied to develop further phenomenological understanding of the influences of welding heat cycle accompanying microstructural changes. Fatigue tests were carried out under constant amplitude of load in air at room temperature. The results showed that the crack propagation rate was different in base metal, heat affected zone and welding line. The crack propagation behavior in each part of duplex stainless steel was strongly dependent on phase ratio(.gamma../.alpha.) and several factors of microstructure also affected this propagation behavior. The fractographic feature in each part of steel were discussed on crack propagation behaviors.