• Proceedings of the KWS Conference
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• 2001.05a
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• pp.75-78
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• 2001

• Journal of the Korean Society for Railway
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• v.12 no.4
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• pp.512-517
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• 2009

Extruded aluminium panels have been widely used for railway vehicle structures because -of their light specific weight and other merits. In the past, GMAW (Gas Metal Arc Welding) and GTAW (Gas Tungsten Arc Welding) were mainly used to join aluminium panels. But recently friction stir welding (FSW) is widely used due to its lots of advantage. In this study aluminium A6005 which is used for car body structures was chosen. The influences of main parameters on mechanical properties such as: pin (tool) rotating speed, pin transition speed, shoulder, diameter, pin length and tilting angle were examined. Optical microscope and scanning electron microscope (SEM) observation, micro hardness tests, and tensile tests were carried out.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.4
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• pp.515-522
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• 2021

In this paper, we present and analyze a method of applying a machine learning to ultrasonic test signals for constant monitoring of the welding faults in a tubular steel tower. For the machine learning, feature selection based on genetic algorithm and fault signal classification using a support vector machine have been used. In the feature selection, the peak value, histogram lower bound, and normal negative log-likelihood from 30 features are selected. Those features clearly indicate the difference of signals according to the depth of faults. In addition, as a result of applying the selected features to the support vector machine, it has been possible to perfectly distinguish between the regions with and without faults. Hence, it is expected that the results of this study will be useful in the development of an early detection system for fault growth based on ultrasonic signals and in the energy transmission related industries in the future.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.50-50
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• 2009

본 연구에서는 차체 부품의 경량소재 대체에 따른 Panel Assembly Rear Seat Back 부품 제작에 최신 저입열 미그용접공정을 적용한 TWB(Tailor Welded Blank) 공정기술을 확보하기 위해 최적 용접조건 도출에 관한 연구를 진행하였다. 용접 후 성형이 이뤄지는 제조공정의 특성 상 성형강도에 중점을 둔 실험을 진행하였으며, 이를 위해 각 와이어에 따른 용접부의 기계/금속학적 특성이 평가되었다. 대상 시편은 6천계열 열처리형 합금이며, 두께는 각각 1.6t, 1.4t로 이를 맞대기 용접 후 그 특성을 평가하였다. 용접은 저입열 GMA용접 공법 중 하나인 CMT 용접법(Cold Metal Transfer)을 사용하였으며, 평가 대상 와이어로는 4043, 4047, 5183 및 5356이 사용되었다. 특성평가는 마크로 및 마이크로 조직, 경도, 인장강도, 기공 및 결함, 성형강도 등에 대해 이뤄졌으며, 희석된 와이어의 조성이 용접부 특성에 미치는 영향에 대해서도 검토되었다. 실험 결과, 5천계열 와이어가 성형강도에 비교적 더 강인한 결과를 나타냈으며 성형강도는 용접조건 및 초기 갭에 대한 영향은 받았으나, 비드형상과 강도간의 연관성은 찾을 수 없었다. 이에 따라 TWB 적용을 위한 와이어로는 5356이 가장 우수한 것으로 판명되었다.

• Journal of Welding and Joining
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• v.21 no.1
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• pp.60-65
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• 2003

At present. welding of most pipes with large diameter is carried out by the manual process. Automation of the welding process is necessary f3r the sake of consistent weld quality and improvement in productivity. In this study, two vision sensors, based on the optical triangulation, were used to obtain the information for seam tracking and detecting the weld defects. Through utilization of the vision sensors, noises were removed, images and 3D information obtained and positions of the feature points detected. The aforementioned process provided the seam and leg position data, calculated the magnitude of the gap, fillet area and leg length and judged the weld defects by ISO 5817. Noises in the images were removed by using the gradient values of the laser stripe's coordinates and various feature points were detected by using an algorithm based on the iterative polygon approximation method. Since the process time is very important, all the aforementioned processes should be conducted during welding.

• Journal of Welding and Joining
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• v.15 no.1
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• pp.36-45
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• 1997

용접 구조물에 대한 프로세스 제어를 위하여 매우 효과적인 수단이 될 수 있는 SYSWELD 소프트웨어의 이론적인 개념 및 응용 기술에 대하여 소개하였다. 전술한 바와 같이 SYSWELD는 일반적으로 알려져 있는 범용 열 및 구조해석 상용 Code와는 달리 야금학적 이론이 접목되므로써 이전에는 고려하기 곤란했던 제어 인자들에 대하여 보다 정확한 정보를 얻을 수 있기 때문에 용접 프로세스 분야에 매우 적합한 시뮬레이션 Code라고 판단된다. 이와 같이 수치해석 기술을 응용함으로써 연구기관에서는 제반 현상들에 대하여 실험적인 접근방법보다 보다 효과적으로 이해할 수 있게 되어 궁극적으로 이론적 발전 및 실용화를 이룰 수 있으며, 또한 산업체에서는 현업에서 발생하는 결함의 제어 및 구조물이나 프로세스의 최적 설계 방안을 수립하는 일이 가능하기 때문에, 현재 용접 분야에 대한 컴퓨터 시뮬레이션 응용 기술에 대하여 관심이 집중되고 있다. 이에 당사는 SYSWELD를 비롯하여 공학 분야의 유용한 상용 Code에대한 공급 및 기술 지원 뿐만 아니라 엔지니어링 능력을 갖추고 이와 같은 추세에 부응하고자 하는 노력중에 있는 바, 용접 시뮬레이션 응용 기술에 대한 현황을 소개하고자 하였으므로 참고가 되기를 바란다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.5
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• pp.129-136
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• 2012

On this study, $CO_2$ gas, net of Ar gas, and mixed gas in solid wire(AWS ER 70S-6) and flux cored wire(AWS E71T-1) were used to weld on Mild steel(SS400). After the progress, the status changes of the welds in Mild steel(SS400) were investigated with compositional changes. For stable experiments, welding was conducted using the automatic feeder. Radiation testing, hardness testing, chemical composition analysis and penetrated cross-section were measured. Through these experiments, shapes of penetrated cross-section, chemical composition changes, and weld defects according to the variation of welding gas were known. Weld defects and weld cross-sectional shapes by the variation of the welding voltage were also detected.

• 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 the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.434-441
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• 2016

Friction Stir Welding (FSW) is a solid-state joining process involving the frictional heat between the materials and tools. The amount of heat conducted into the workpiece determines the quality of the welded zone. Excessive heat input is the cause of oxides and porosity defects, and insufficient heat input can cause problems, such as tunnel defects. Therefore, analyzing the temperature history and distribution at the center of the Friction Stir Welded zone is very important. In this study, the temperature distribution of the friction stir welding region of an AZ61 magnesium alloy was investigated. To achieve this goal, the temperature and metal flow was predicted using the finite element method. In FE analysis, the welding tool was simplified and the friction condition was optimized. Moreover, the temperature measuring test at the center of the welding region was performed to verify the FE results. In this study, the tool rotation speed was a more dominant factor than the welding speed. In addition, the predicted temperature at the center of the welding region showed good agreement with the measurement results within the error range of 5.4% - 7.7%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.278-284
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• 2017

In this study, the heat input conditions suitable for the AZ61 magnesium alloy were derived by controlling the welding speed at a constant rotational speed. In addition, from an economic point of view, industry demands higher welding speeds. Therefore,the effects of the welding speed were studied. The rotational speed applied was 800rpm, and the welding speed was varied from 100 to 500mm/min to evaluate the behavior of the welded regions. Tensile and hardness tests were conducted to examine the mechanical properties. Optical microscopy was used to observe the microstructure and soundness of the welded regions. Defects were observed at the welded region when the welding speed was more than400mm/min. As the welding speed increased, the grain size of the stir zone decreased and the hardness tended to increase proportionally. When the rotational speed was 800 rpm and the welding speed was 200mm/min and 300mm/min, there wereno defects in the welded region and excellent mechanical properties were recorded. In addition, the joint efficiencies were 100.5% and 101.2%, respectively, and the ultimate tensile strength was similar to that of the base metal. Fracture of the tensile specimen occurred between the advancing side and stir zone, and the fracture location coincided with the region where the hardness decreased temporarily.