• Journal of Welding and Joining
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• v.32 no.4
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• pp.15-19
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• 2014

Additive manufacturing technology is taking great attentions in these days because the term 3D-printing became a hot issue as the next generation manufacturing paradigm. Especially, laser additive manufacturing is at the center of interest thanks to the accuracy compared to other heat sources. In this report, recent papers about laser additive manufacturing are analyzed and reviewed. General technology is specified into three different categories and they are laser sintering, laser melting and laser metal deposition. Similarities and differences are clearly described by detailed technologies and used materials type. Representative application examples are selected then future of this technology is expected through those applications. Additionally, market of laser additive manufacturing systems itself and application fields are also predicted based on present 3D-printing market and technical progressions.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.672-678
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• 1993

The bead shape in high frequency electric resistance (HER) pipe welding gives important information ons judging current welding state. In most manufacturing process, the heat input is controlled by skilled operators observing color and bead shape. We proposed the bead shape monitoring system in HERW pipe process by using structured light beam. We reconstructs 3-D shape of bead from the measured data, and compare this shape with real 3-D shape obtained by coordinate-measuring machine. This experiment results show that the proposed system can monitor the bead shape with good accuracy.

• Journal of Welding and Joining
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• v.21 no.6
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• pp.40-45
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• 2003

Steel members have advantages of resisting torsion and axial compression. In design, residual stresses at the welded joint of T-shape steel pipes are one of the most important points to be considered. In this paper, characteristics of residual stresses of welded joints are clarified by carrying out 3D non-steady heat conduction analysis and 3D thermal elastic-plastic FE-analysis. According to the results, the production mechanism of residual stresses at the welded joint of T-shape steel pipe is clarified. In this paper, circumferential stresses depended on thermal histories but axial and radial stresses were more dependent on geometrical shape than thermal histories. Residual stresses in the axial direction on the lower part of pipe member were tensile, controlled by geometrical shape. However, in case of middle part, residual stresses in all the directions were controlled by thermal histories.

• Journal of Welding and Joining
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• v.34 no.4
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• pp.9-16
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• 2016

Metal parts are produced by conventional methods such as casting, forging and cutting, extrusion, etc. However, nowadays, with additive manufacturing (AM), it is possible to directly commercialize by means of stacking of equipment to the 3D drawing and use of high precision tools such as laser source. Thus, drawing of materials is an important aspect in delivering good products. AM deals with production of lighter aircraft parts and few more three-dimensional molds, it wish to manufacture special medical parts and want to steadily expand the new market area. The cost of related equipment and materials are still expensive and difficult to obtain on a mass production. However, the ability to make changes and lead the innovation in the paradigm of traditional manufacturing process is still effective. In this paper, we introduce metal AM and the principles of the related devices, metal powder production process, and their application.

• Journal of Welding and Joining
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• v.20 no.5
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• pp.78-86
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• 2002

A metallurgical model for the prediction of prior austenite grain size considering the dissolution kinetics of M$_3$C precipitates at the heat affected zone of SA508-cl.3 was proposed. The isothermal kinetics of grain growth and dissolution were respectively described by well-known equation, $dD/dT=M({\Delta}F_{eff})^M$ and Whelan's analytical model. The isothermal grain growth experiments were carried out for measure the kinetic parameters of grain growth. The precipitates of the base metal and the specimens exposed to thermal cycle were examined by TEM-carbon extraction replica method. The model was assessed by the comparison of BUE simulation experiments and showed good consistencies. However, there was no difference between the model considering and ignoring $M_3C$ precipitates. It seems considered that pinning force exerted by $M_3C$ Precipitates was lower than driving force for grain growth due to large size and small fraction of precipitates, and mobility of grain boundary was low in the lower temperature range.

• Journal of Welding and Joining
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• v.31 no.6
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• pp.77-83
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• 2013

3D packaging technology using TSV (Through Silicon Via)has been studied in the recent years to achieve higher performance, lower power consumption and smaller package size because electrical line is shorter electrical resistivity than any other packaging technology. To stack TSV chips vertically, reliable and robust bonding technology is required because mechanical stress and thermal stress cause fracture during the bonding process. Cu pillar/solder ${\mu}$-bump bonding process is usually to interconnect TSV chips vertically although it has weak shape to mechanical stress and thermal stress. In this study, we suggest Insert-Bump (ISB) bonding process newly to stack TSV chips. Through experiments, we tried to find optimal bonding conditions such as bonding temperature and bonding pressure. After ISB bonding, we observed microstructure of bump joint by SEM and then evaluated properties of bump joint by die shear test.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.6
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• pp.821-830
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• 2010

Deck plates and hatch coming of large container carrier and offshore structures are joined by ultra-thick plates whose thickness is more than 60mm. Traditionally FCAW has been used to join the thick plates in butt joint. However, FCAW has been replaced with EGW since the welding efficiency of EGW is higher than that of FCAW. Tandem EGW using two electrodes has been applied to vertical position welding by several shipyards. EGW requires one or two layers of bead whereas FCAW requires more than 20 layers of weld bead in thick welding. However, high welding residual stresses are generated by EGW since it uses higher heat input than FCAW. In the present study, a finite element model is suggested to predict the residual stresses induced by the tandem EGW. Butt specimen of EH40 TMCP shipbuilding steel plates vertical welding was modeled by a three-dimensional model. Residual stresses were measured by X-ray diffraction method and to verify the numerical result. The results show a good agreement with experimental result.

• Journal of Welding and Joining
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• v.11 no.3
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• pp.34-47
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• 1993

Finite element models were developed for thermal and residual stress analysis for the specific welding problems. They were used to evaluate the effectiveness of the various welding heat input models, such as ramp heat input function and lumped pass models. Through the parametric studies, thermal-mechanical modeling sensitivity to the ramp function and lumping techniques was determined by comparing the predicted results with experimental data. The kinetics for residual stress formation during welding can be developed by iteration of various proposed mechanisms in the parametric study. A ramp heat input function was developed to gradually apply the heat flux with variable amplitude to the model. This model was used to avoid numerical convergence problems due to an instantaneous increase in temperature near the fusion zone. Additionally, it enables the model to include the effect of a moving arc in a two-dimensional plane. The ramp function takes into account the variation in the out of plane energy flow in a 2-D model as the arc approaches, travels across, and departs from each plane under investigation. A lumped pass model was developed to reduce the computation cost in the analysis of multipass welds. Several weld passes were assumed as one lumped pass in this model. Recommendations were provided about ramp lumping techniques and the optimum number of weld passes that can be combined into a single thermal input.

• Journal of Welding and Joining
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• v.28 no.2
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• pp.84-90
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• 2010

Fillet welding accounts for about 80% of all constructing process of ship and ocean structure. T-joint is one of the typical shapes which are frequently reported to experience the fatigue damage when the marine structure meets the storm loads. The fatigue damage is affected by the magnitude of residual stresses on the weld. Recently, many shipping registers and design guidances have required that the fatigue strength assessment method should be compensated by the effect of the residual stress in case that the random loading or storm loading is applied to the marine vessels. This study suggests the computational procedure to analyze the residual stresses of T-joint specimen that is frequently reported to get damaged by the storm loading. Experiment by XRD as well as the 3-D computational welding model is presented in order to get the profile of residual stress. Throughout the comparison of experimental result with the computational result, the computational model was validated. Thereafter, characteristics of he residual stresses in the joint are discussed.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.84-84
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• 2009

파이프라인을 건설함에 있어 가장 중요한 기술이 배관 용접기술이다. 즉 파이프와 파이프를 연결하는 작업이 공사 진척도를 결정하기 때문에, 이를 얼마나 경제적으로 신속하게 수행해 나가느냐하는 것은 건설기간 및 건설비용을 결정하는 핵심 요소이다. 가스배관 시공 원주용접 방법은 여러 가지 있는데, 현재 국내에서는 전량 수동용접을 채택하고 있다. 이 방법은 국내 가스배관을 건설한 초기부터 적용해온 것으로 우수한 품질을 확보할 수 있으며, 취약한 국내 자동화기술과 열악한 도로 매설 시공여건에서 적용하기 용이한 방안이다. 그러나 우수한 용접기량을 보유한 용접사가 점차 부족해지고, 배관시공 시간을 단축하고 비용을 줄이기 위한 필요성이 점차 커지면서 이를 해결할 수 있는 기술로서 자동원주용접방안이 있다. 이 기술들은 해외 가스배관에 이미 오래전부터 적용되어 용접부위 신뢰성과 품질 우수성을 확보하고 시공비용절감을 달성하고 있다. 자동용접을 적용하기 위해서는 용접절차를 수립하여 절차인증시험을 수행하고, 기존방안과 동일이상의 품질이 확보되며 효율성을 겸비해야만 한다. 국가 기본에너지의 안정적인 공급을 위해 적기 시공이 필요하고, 1 km당 10 억원 이상이 소요되는 배관시공비용 중 약 1/3이 용접비파괴검사 비용인 점을 감안할 때 품질이 확보되면서 경제적인 시공방안이 있다면 이를 적용하는 것이 국가 산업 경제적 측면에서 필요한 일이다. 이와 관련된 연구에서는 국내 가스배관 원주용접에 적용 가능한 용접공정을 검토하고, 용접절차를 수립하여 절차인증시험을 수행하였으며, 추가로 배관 원주 자동용접부위에 대한 기계적 특성 평가를 실시하였다. 현재 국내 건설여건과 비파괴검사 기준을 만족시키고 안전성과 효율성을 겸비한 방법으로는 초층과 2층은 수동 GTAW를 적용하고 나머지 층은 반자동 FCAW를 적용하는 방안이 적절한 것으로 판단된다. 전 층을 자동 GTAW로 용접하는 방안은 품질은 확보되지만 효율성측면에서 대형배관에는 적용하기 어려울 것으로 보이며, 해외에서 많이 사용되는 자동 GMAW 방안은 국내 비파괴검사기준을 만족시키기 어려워 검토대상에서 제외하였다. 본 논문에서는 두 가지 용접방법에 대한 용접공정개발과정과 원주용접부위 기계적 특성을 검토하여 최적방안을 제시하고자 한다.