• Journal of Advanced Marine Engineering and Technology
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• 제35권1호
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• pp.75-81
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• 2011

이종합금인 알루미늄 합금 6061-T6와 알루미늄 합금 5083-O의 용접을 위해 마찰교반 용접기술을 사용하였다. 마찰교반 용접된 이종 접합부에 대하여 기계적 특성, 경도 및 조직변화를 관찰하였다. 용접재의 기계적특성은 후진 측에 위치한 알루미늄 합금의 교반영역에 형성되는 미세조직이 주요한 변수로 작용하였다. 이종 알루미늄 합금이 교차한 양파 모양 형상의 얇은 층을 이루었다. 미세조직관찰에서 공구회전방향과 무관하게 이종합금 접합부에 기공이 관찰되지 않았으나 6061-T6 쪽 열영향부 영역에서 결정립 조대화기 뚜렷하였다. 본 논문의 연구결과, 결함이 없는 최상의 용접조건은 Al 6061-T6를 공구 진행방향에 전진 측에, Al 5083-O를 후진 측에 위치하고, 이송속도 124 mm/min, 1250 rpm의 공구의 회전수, 5 mm의 프루브 직경, 4.5 mm의 프루브 길이, 20 mm의 공구어깨, $2^{\circ}$의 공구 경사각 이다. 이때 용접재의 최대인장강도는 231 MPa이였고, 항복강도는 121 MPa을 나타내었다.

• Journal of Advanced Marine Engineering and Technology
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• 제26권4호
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• pp.464-471
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• 2002

Porosity formation in partial penetration welds by high power lasers is a serious problem in industry. There are two main causes that induce porosity formation. One form of porosity is due to gases (e.g. hydrogen, oxygen) dissolving into the weld pool because of the high temperature and then the rapid solidification traps gases as a bubble in the weld metal. The second problem is voids formed by the keyhole collapsing due to unstable keyhole fluid dynamics. The voids that form at the bottom of the keyhole are relatively large and irregular in shape compared to the gas bubbles; this void formation is the primary concern in this paper. The reduction of voids formed by keyhole collapse is achieved by improving the stability of keyhole. Two methods to improve keyhole stability are discussed in this paper: pulse modulation and beam incident angle. Pulse modulation of the laser beam was performed between 100 Hz and 500 Hz to find out the optimum frequency for the keyhole dynamics. The incident beam angle changed the impact angle of the laser beam to the work surface in a range of 0 to 25 degrees. Glycerin in a semi-solidified state is used as a medium for performing the welding because its transparency allows of visualization of the keyhole.

• 해양환경안전학회지
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• 제12권2호
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• pp.151-155
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• 2006

용접은 가장 널리 사용되는 금속접합기술이며 조선, 자동차, 항공, 플랜트설비 등 산업현장의 여러 분야에서 활용되고 있는 근대산업의 기본적인 생산기술이다. 그러나 용접작업 자체가 강한 빛과 전류, 유해가스등을 발생하고 있으며, 다품종 소량 생산하는 작업장에서는 규격화된 물건을 만들어 내는 제조업에 비해서 자동화가 어렵다. 따라서 범용적으로 모든 형태의 용접할 부위인 용접선을 검출하여 자동으로 용접하기란 상당히 어려우며, 본 논문에서는 삼각파 형태의 굴곡을 가진 용접선을 검출하고자 스트레인게이지를 응용한 센서를 이용하였고, 이를 직선구동이 가능한 반자동 캐리지에 탑재하여 용접선을 자동으로 추적하여 용접하는 실험을 제안하였다. 캐리지는 직선 전진만 하고 있더라도 굴곡이 있는 용접선을 자동으로 검출하여 용접이 가능하도록 하였다.

• Journal of Welding and Joining
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• 제16권6호
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• pp.68-76
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• 1998

A CCD camera with a laser stripe was applied to realized the automatic weld seam tracking. The 3-dimensional information obtained from the vision system made it possible to generate the weld torch path. The adaptive Hough transformation was used to extract laser stripes an to obtain specific weld points. It takes relatively long time to process image on-line control using the basic control using the basic Hough transformation, but it has a tendency of robustness over the noises such as spatter. For this reason, it was complemented with adaptive Hough transformation to have an on-line processing ability for scanning specific weld points. The dead zone, where the sensing of weld line is impossible, was eliminated by rotating the camera with its rotating axis centered at the weld torch. When weld lines were detected, the camera angle was controlled in order to get the minimum image data for sensing of weld lines. Consequently, the image processing time was reduced.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.1278-1280
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• 2004

In this paper, we propose a new diagnosis method of DC/DC converter aging. The method is based on the variations of parasitic resistor for the aging process. We apply an on-line diagnosis of DC/DC converter because the observation is not a device, but a system. This study proposes a method of DC/DC converter diagnosis by analyzing the variations of model on the variations of parasitic resistor.

• 한국산학기술학회논문지
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• 제18권5호
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• pp.278-284
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• 2017

본 연구에서는 일정한 회전 속도에서 용접 속도를 제어하여 AZ61 마그네슘 합금에 적합한 입열량 조건을 도출하였다. 또한 산업적 측면에서는 더 빠른 용접 속도가 요구되기 때문에 용접 속도에 따른 효과를 연구하였다. 회전 속도 변수는 800rpm으로 일정하게 적용하였고, 용접 속도는 100 - 500mm/min 으로 변화시켜 용접부의 거동을 관찰 및 평가하였다. 기계적 물성 평가를 위하여 인장 및 경도 시험을 수행하였으며, 미세구조 관찰과 용접부의 건정성을 판단하기 위하여 광학현미경을 사용하였다. 용접 속도가 400mm/min 이상 적용되었을 때 용접부 내부에서 결함이 관찰되었다. 용접 속도가 증가할수록 교반부의 결정립 크기는 작아졌으며, 경도 또한 비례 증가하는 경향을 보였다. 회전속도 800rpm, 용접 속도 200mm/min과 300mm/min 일 때, 용접부 내 외부 적으로 결함이 없었으며, 우수한 기계적 물성이 기록되었다. 이때, 접합 효율은 각각 100.5%, 101.2%이었고, 최대인장강도가 모재의 강도와 유사하였다. 인장 시편의 파괴는 시편의 전진측과 교반부 사이에서 발생하였으며, 이는 횡단면부 경도 분포에서 경도가 일시적으로 감소하는 위치와 일치하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제33권1호
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• pp.104-111
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• 2009

This paper shows the behaviors of macro- and micro-structures and mechanical properties for specimen's welding region welded by FSW. according to welding conditions with 5mm thickness aluminum 5083O alloy plate. It apparently results in defect-free weld zone in case traverse speed was changed to 32 mm/min under conditions of anti-clockwise direction and tool rotation speed such as 800 and 1250 rpm with tool's pin diameter of 5 ${\Phi}mm$ and shoulder diameter of 20 ${\Phi}mm$, pin length of 4.5 mm and tilting angle of $2^{\circ}$. The ultimate stress of ${\sigma}_T=331$ MPa and the yield point of 147 MPa are obtained at the condition of the travel speed of 32 mm/min with the tool rotation speed of 1250 rpm. There is neither voids nor cracks on bended surface of $180^{\circ}$ after bending test. The improvement of toughness after impact test was found. The lower rotating and traverse speed became, the higher were yield point, maximum stress and elongation(%) with the stresses and the elongation(%) versus the traverse speed diagram. Vickers hardness for cross section of welding zone were also presented. The typical macro-structures such as dynamically recrystallized zone, thermo-mechanically affected zone and heat affected zone and the micro-structures of the transverse cross-section were also showed. However, the author found out that the region of 6mm far away from shoulder circumference was affected by friction heat comprehensively, that is, hardness softened and that part of micro-structures were re-solid-solution or recrystallized, the author also knew that there is no mechanically deformation on heat affected zone but there are the flow of plastic deformation of $45^{\circ}$ direction on thermo-mechanically affected zone and the segregation of Al-Mg on nugget. The solid solution wt(%) of parent material as compared against of friction stir welded zone was comprehensively changed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 심포지엄 논문집 정보 및 제어부문
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• pp.225-227
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• 2008

In this paper, universal wireless remote controllers are proposed. It can be used for general welding power sources. Sometimes, wireless remote controllers for welders are needed because welding torches are far away from welding sources in the case of big ship-building or big tank constructions. In order to use the wireless remote controllers, digital cpu-based welding systems are essential for digital interfaces. But, in this paper, using digital resistors makes wireless remote controllers be easily applied to digital or analog welders. To demonstrate the practical significance of our results, some experimental results are presented.

• 대한예방의학회:학술대회논문집
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• 대한예방의학회 1995년도 제47차 추계 학술대회 연제집
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• pp.251-252
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• 1995

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.1105-1109
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• 1995

A CCD-camera, which is structured with vision system, was used to realize automatic seam-tracking system and 3-D information which is needed to generate torch path, was obtained by using laser-slip beam. To extract laser strip and obtain welding-specific point, Adaptive Hough-transformation was used. Although the basic Hough transformation takes too much time to process image on line, it has a tendency to be robust to the noises as like spatter. For that reson, it was complemented with Adaptive Hough transformation to have an on-line processing ability for scanning a welding-specific point. the dead zone,where the sensing of weld line is impossible, is eliminated by rotating the camera with its rotating axis centered at welding torch. The camera angle is controlled so as to get the minimum image data for the sensing of weld line, hence the image processing time is reduced. The fuzzy controller is adapted to control the camera angle.