• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1317-1323
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• 2010

In this study, the weld residual stress distribution at a dissimilar-metal welded plate of low alloy carbon steel and stainless steel, which are widely used in nuclear power plants, was characterized. A plate mock-up with butt welding was fabricated using SA 508 low alloy steel and Type 304 stainless steel plates and the residual stresses were measured by the X-ray diffraction method after electrolytic polishing of the plate specimen. Finite element analysis was carried out in order to simulate the butt welding of dissimilar metal plate, and the calculated weld residual stress distribution was compared with that obtained from the measured data. The characteristics of the three-dimensional residual stress distribution in a butt weld of dissimilar metal plates were investigated by comparing the measured and calculated residual stress data.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.10
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• pp.901-906
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• 2016

The purpose of this study is to improve productivity by implementing one-pass full penetration welding using laser-arc hybrid welding for AH36. On increasing the thickness of the plate, a higher power of laser and arc was required to obtain full penetration. However, increasing the power of heat source caused undercut defects at both ends of the bead. This undercut was prevented by controlling the parameters of welding voltage and pulse correction. Hardness measurement and tensile test were conducted to apprehend the mechanical properties of weld. Also, by carrying out the microstructure observation for laser and arc regions, microstructural properties were understood.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.4
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• pp.517-523
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• 2009

Magnesium alloys have many advantages such as a low density, high strength/weight ratio and well recycle. And joining process is absolutely necessary to expand the field of application of magnesium alloy. The main problems of conventional process such as arc welding for magnesium alloy are the inflammability, a tendency toward crack formation and the appearance of porosity during solidification. Laser welding technology is a promising means for overcoming these difficulties. This study is related to the laser weldability of AZ31 magnesium alloy, an all-purpose wrought alloy with good strength and ductility. The effect of welding conditions on the weldability of butt joints was examined. Also, the mechanical properties of butt welded joints were investigated by tensile test and hardness test.

• Journal of Korean Society of Steel Construction
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• v.14 no.2
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• pp.385-394
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• 2002

Currently, high strength steel is not used for steel bridges in Korea, except for the SM570 high strength steel in very isolated cases. The study aimed to promote the active adaptation of high strength steel for long-span steel bridges. Thus, the fatigue behavior of SM570 and POSTEN80 high strength steel was investigated. For the experimental study, the butt welded joints samples were manufactured. Likewise, regular amplitude tensile fatigue tests were conducted. Test results, e.g., location of fatigue cracks and their propagation were compared with the findings of other researchers. After analyzing the effects of fatigue strength, e.g., static tensile strength and plate thickness of base metal, basic data for fatigue design criteria of SM570 and POSTEN80 high strength steel were presented.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.2021-2026
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• 2013

In this study, the effect on the welding angle distortion was reviewed by carrying out a thermal elastic-plastic analysis while changing the cooling condition(width, length, and distance from weld torch to cooling torch) the back of the welding zone for the butt weld joint. The review results revealed that maximum 57% of reduction in the angle distortion was achieved when the distance between weld torch and cooling tip of 25mm, cooling length of 80mm, and cooling width of 30mm were maintained.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1091-1092
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• 2013

• Proceedings of the Korean Society of Laser Processing Conference
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• 2004.10a
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• pp.78-81
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• 2004

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.4
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• pp.871-877
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• 2008

It is important to investigate the relationship between weld process parameters and weld bead geometry for adaptive arc robot welding. Howeve, it is difficult to predict an exact back-bead owing to gap in process of butt welding. In this paper, the quantitative prediction system to specify the relationship external weld conditions and weld bead geometry was developed to get suitable back-bead in butt welding which is widely applied on industrial field. Multiple regression analysis for the prediction of process parameters was used as the research method. And, the results of the prediction method were compared and analyzed.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1747-1751
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• 2003

The paper shows properties such as vickers hardness, yielding and ultimate stresses for the weld zone of the butt and the lap jointed specimens, and compare maximum loads, stress-strain curves, deformation appearance after guided bending test and fracture appearance for butt and lap jointed specimens. The research in this experiment also shows the weldability of the butt joint specimen is better than that of the lap joint specimen using FSW with $2mm^{t}$ aluminum alloy sheet in milling machine.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2011.06a
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• pp.76-76
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• 2011

선박이나 산업 플랜트에서 파이프 또는 탱크류의 맞대기 용접 시 안정적인 이면비드의 형성은 매우 중요하다. 대부분의 현장에서 파이프 맞대기 초층용접부의 안정적인 이면비드를 형성하기 위해 3mm의 루트갭을 띄우고 루트면이 없는 V-그루브에서 필러를 사용하는 수동 TIG용접을 주로 사용하고 있다. 수동 TIG용접은 고품질의 비드와 우수한 아크안정성, 그리고 용접인자의 제어가 쉽다는 장점이 있다. 그러나 수동 TIG용접은 용접속도가 10cpm정도로 느리기 때문에 GMAW에 비해 생산성이 낮고 작업자의 숙련도에 따라 품질이 변하게 된다. 본 연구에서는 높은 생산성과 기준갭 1.5mm에서 단차의 허용공차를 크게 하기 위해 루트면 3mm를 가지는 U-그루브의 설계를 하였으며, 두꺼운 루트면을 가지는 그루브에서 안정적인 이면비드를 형성시키기 위해 GMAW에서 아크 충격량에 대한 검토를 실시하였다. GMAW의 아크력이 용입에 어떠한 영향을 미치는지 검토하기 위해 수냉되는 동판에 갭을 1.5mm 띄우고 동일한 용착량과 입열량에서 아크력만을 변화시켜 실험하였다. 또한, U-그루브의 루트부를 모델링하여 두께3t의 평판시편을 각각의 갭과 단차 조건에서 실험하였다. 이 때, 기준갭 1.5mm에서 갭에 의해 생기는 단면적을 기준 갭단면적, 갭이 증가함에 따라 증가되는 단면적을 추가 갭단면적, 갭이 감소함에 따라 감소하는 단면적을 감소 갭단면적으로 정의하였다. 용접 중 발생하는 추가, 감소 갭단면적에 대하여 용착량을 50%의 수준으로 증가, 감소 시켰다. 갭에 따라 아크력을 변경하여 실험을 실시하였고 이면비드의 형상을 확인 하였다. 마지막으로 평판 시편의 조건에서 안정적으로 이면비드가 형성된 조건을 pipe U-그루브에 적용하였다. 그 결과 동판에서 용착량과 입열량이 같음에도 불구하고 아크력이 증가함에 따라 용입이 깊어짐을 확인하였다. 또한. 3t 평판시편에서 아크력의 제어를 통해 큰 단차와 갭이 있을 때, 안정적인 이면비드를 얻을 수 있는 조건을 확립하였다. 마지막으로 pipe U-그루브에서 앞선 실험의 용접조건으로 갭과 단차의 변화에 대해 실험을 하였으나, 시험편의 두께차이에 의한 전도 열손실로 인해 이면비드의 형성이 어려웠고, 아크 충격량의 증가를 통해 이러한 문제를 해결하였다.