• 비파괴검사학회지
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• 제21권1호
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• pp.46-53
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• 2001

음향방출 신호를 이용하여 분류기를 설계하는 과정에서의 특징값 선택법에 관해 연구하였다. 분류기는 역전파법을 이용한 신경망 분류기를 사용하였다. Fisher's criterion, class mean scatter criterion, eigenvector analysis와 함께 본 논문에서 새로 제안하는 특징값 공간에서의 특징값 좌표사이의 차이를 이용하는 2-D criterion, 3-D criterion을 이용해서 특징값을 선택하고 각각에 대해 분류기를 설계하여, 인식률과 수렴속도를 비교하였다. 분류를 위한 자료를 얻기 위하여 용접부 결함시편과 로터리 압축기 금속 접촉부 결함시편을 사용하였다. 인식률 면에서 2-D criterion과 3-D criterion이 우수한 결과를 나타내었다.

• 한국정보통신학회논문지
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• 제26권4호
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• pp.556-561
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• 2022

본 논문에서는 선박 용접공정에 사용되는 장비에 전력선통신 기술을 접목하고 금속블록을 통신매체로 사용하는 블록매체통신시스템을 제시한다. 여기서는 디지털 피더와 금속블록을 지지하는 핀지그에 유도성 커플러를 설치하고, 피더에 연결된 용접건에서 발생되는 전류에 정보신호를 더하여 금속블록에 인가함으로써 작업이 시작되면 현장에서 발생되는 정보를 상황실 서버에 실시간 전송한다. 현장시험 결과, 제시된 블록매체통신시스템의 송신부에서 전송된 데이터는 상황실 서버컴퓨터에 정확하게 수신되는 것을 확인하였다. 따라서 제시된 시스템은 기존 용접공정에 대한 변경 없이 구축이 가능하므로 향후 조선소 스마트 팩토리화를 통한 조선산업의 경쟁력 강화에 도움이 될 것으로 기대된다. 또한 전자파 차폐 환경이나 밀폐된 공간에서 작업자에게 발생할 수 있는 응급상황에 신속한 대처가 가능하므로 산업재해 예방효과도 클 것으로 사료된다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1560-1565
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• 2005

Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and deep penetration. The thermal cycles associated with laser welding are generally much faster than those involved in conventional arc welding processes, leading to a rather small weld zone. Experiments are performed for 304 stainless steel plates changing several process parameters such as laser power, welding speed, shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between the similar and dissimilar plates, etc. The following conclusions can be drawn that laser power and welding speed have a pronounced effect on size and shape of the fusion zone. Increase in welding speed resulted in an increase in weld depth/ aspect ratio and hence a decrease in the fusion zone size. The penetration depth increased with the increase in laser power.

• 한국정밀공학회지
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• 제23권3호
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• pp.47-55
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• 2006

Laser welding of dissimilar metals has been widely used to improve a wear resistance and a corrosion resistance of the industrial parts. The objective of this research is to investigate the influence of the process parameters, such as the welding for SM45C and STS304 with CW Nd:YAG lasers. The bead-on-plate welding tests are carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the dissimilar welding, the welding quality of the cut section, stress-strain behavior and the hardness of the welded metal are investigated. From the results of the investigation, it has been shown that the optimal voiding condition without defects in the vicinity of the welded area and with a good welding quality is 1600W of the laser power, 0.85m/min of welding speed and $4{\ell}/min$ of pressure for shielding gas.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.17-18
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• 2006

Laser welding of metals has been widely used to improve a wear resistance and a corrosion resistance of the industrial parts. The objective of this research works is to investigate the influence of the process parameters, such as the welding for metals with CW Nd:YAG lasers. The bead-on-plate welding tests are carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the butt welding, the welding quality of the cut section, stain-stress behavior and the hardness of the welded part are investigated. From the results of the investigation, it has been shown that the optimal welding condition without defects in the vicinity of the welded area and with a good welding quality is 1400W of the laser power, 0.8m/min, 0.9m/min of welding speed and $4{\ell}$ in of pressure for shielding gas.

• 한국자동차공학회논문집
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• 제17권3호
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• pp.35-44
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• 2009

The purpose of this paper is to describe experimental results about the T-joint welding of the high power continuous wave (CW) fiber laser for SAPH steel plate for seat frame of car. The seat rail is a part of seat frame of cars. The assembling method is mostly fix up using a bolt and nut. But this assembling method has many demerits in productivity such as increasing work process and material cost. This paper presents an experimental study about Laser T-Joint weldability of seat rail. Laser welding has many advantages in lightness and saving material costs of seat frame. The laser beam was moved along the work pieces by six axis robot with process optical fiber. The laser beam is focused with a welding head within incident angle $15{\sim}45^{\circ}$ for the purpose of the T-joint welding through two side full penetration. The range of the root gap size is less than ${\leq}0.4mm$. Optical microscopy SEM were performed to observe the micro structures and determine the structures of welded zone.

• 전자공학회논문지 IE
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• 제48권1호
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• pp.16-24
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• 2011

본 논문에서는 트림 T형 용접너트 생산 시스템 중 불량품을 자동으로 선별할 수 있는 자동 선별기를 비전 검사기를 사용하여 개발하였다. 카메라로부터 입력되는 영상 신호에 대해 히스토그램을 활용한 경계 판별 및 나사산 검출, 이진 모폴로지 연산(Binary morphology operation)을 활용한 얼룩 검출 등의 기법을 활용하였다. 기존의 검사기나 육안 검사에서 불가능하였던 수치 검사를 0.1mm의 정밀도로 검사할 수 있도록 하였으며, 이를 통해 제조단가를 25% 절감하고 생산성을 330% 이상 향상시킬 수 있었다.

• 한국가스학회지
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• 제12권2호
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• pp.53-56
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• 2008

용접 부위의 결함을 비파괴적으로 탐지하기 위하여 홀센서에 의해 누설자속을 측정할 수 있는 시스템과 4 종류의 용접결함을 갖는 기준시편을 제작하였다. 제작한 시스템으로 시편에 생성시킨 4 종류의 결함에서 누설된 자속을 측정하였고, 신호의 피크-피크 크기와 피크-피크 간의 간격에서 결함의 종류를 구분할 수 있는 가능성을 확인하였다.

• Journal of Welding and Joining
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• 제30권4호
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• pp.24-30
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• 2012

Laser welding by fiber laser accompanied by a lot of spatter and humping bead. This is because the deep and narrow keyhole usually form due to high beam quality. So the weld bead is formed defects, because the plasma jet with a high vapor pressure make the molten pool on keyhole wall scattered. For such a reason, unstable behavior of keyhole is difficult to monitor laser welding by using the laser induced plasma. Mostly, fiber laser welding of thick plates most be influenced by this effect. Therefore, fiber laser welding has been difficult to apply the sole. Thus, laser welding monitoring based on plasma measurements have much difficulty in measurements and analysis of signal. In this study, influence of the plasma emission signal according to welding speed and laser power in fiber laser welding analysed by using RMS and FFT analysis. We can verify that RMS value of the plasma emission signal changes with welding parameters in fiber laser welding, and aspect ratio greater than 1, the peak of FFT frequency had been moved in accordance with welding parameter.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.203-208
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• 2004

The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and deep penetration. Welding characteristics of Inconel 600 Alloy using a continuous wave Nd:YAG laser are experimentally investigated. The major process parameters studied in the present laser welding experiment were position of focus, laser power, travel speed. The gap and offset maintained as small as possible. Optical microscope were used to investigate the microstructures of the welded zone. The follow conclusions can be drawn the laser power and travel speed have a pronounced effect the fusion zone size and shape.