• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1999년도 특별강연 및 추계학술발표대회 개요집
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• pp.43-46
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• 1999

It has been suggested that the motivation for automation of welding processes ncludes the replacement and extension of the functions of human operators. Among these types of the welding automation, SAW(Submerged Arc Welding) was prevalently used, because it is highly suited to a wide range of application, especially for the high speed welding. A Significant portion of the total manufacturing time for a pipe fabrication process is spent on the welding following primary machining and fit-up processes. To achieve the reliable weld bead appearance, the automatic seam tracking and adaptive control to fill the groove are urgently needed. This paper proposed the mechanical functions of multi-torches welding system, flux supply and recovery system in conjunction with the complex air pulsing method and various types of methodologies. It was shown that the multi-torches welding system revealed the high welding qualities for the circular and rectangular pipes. In conclusion, the multi-torches welding system developed will contribute the advanced welding technology, welding automation and increment of the market in these areas.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.670-677
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• 2003

Although Gas Tungsten Arc Welding (GTAW or TIG welding) is considered as high quality and precision welding process, it also has demerit of low melting rate. Narrow-gap TIG welding which has narrow joint width reduces the groove volume remarkably, so it could be shorten the welding time and decrease the overall shrinkage in heavy wall pipe welding. Generally Narrow-gap TIG welding is used as orbital welding process, it is important to select the optimum conditions for the automatic control welding This paper looks at the application and metallurgical properties on Narrow-gap TIG welding joint of heavy wall large austenitic stainless steel pipe to determine the deposition efficiency, the resultant shrinkage and fracture toughness. The fracture toughness depends slightly on the welding heat input.

• 대한기계학회논문집A
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• 제34권1호
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• pp.79-83
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• 2010

최근 원자력발전소 배관계의 용접 시 결함 발생의 원인이 되는 용접변형과 용접잔류응력을 감소시키고 용접 효율도 증가시키기 위해 협개선 용접법이 적용되고 있다. 협개선 용접법은 기존 용접법에 비해 상대적으로 입열량이 적고 용접변형과 용접잔류응력도 감소시킬 수 있기 때문에 배관 건전성 관점에서 많은 이점이 있을 수 있다. 그러나 실제 협개선 용접부 결함에 대한 정확한 파괴역학적 분석 등을 위해서는 용접 특성을 고려하여 변형 및 용접잔류응력 특성을 정확하게 예측해야 한다. 따라서 본 논문에서는 협개선 용접부에 대한 상세 2차원 유한요소해석을 수행하여 협개선 용접부의 용접잔류응력 분포를 결정하였으며, 이를 일반적인 용접법에 대한 특성과 비교하였다. 본 논문의 결과는 향후 협개선 용접부의 결함 평가와 용접방법 개선 등을 위해 적용될 수 있다.

• 한국정보통신학회논문지
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• 제6권8호
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• pp.1374-1380
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• 2002

용접을 하는데 있어서 보다 균일한 용접상태를 유지하고, 용접품질의 향상 및 동일시간에 보다 많은 용접을 함으로써 생산성 향상을 위해 로봇의 이용이 점차로 증가하고 있다. 로봇용접의 과정 중 실제 용접을 실시하기 위해 로봇을 움직이기 이전에 용접할 부위의 검출이 선행되어야 하고, 그 검출방법에 있어서 크게 접촉식과 비접촉식의 센서가 활용이 되고 있다. 본 논문에서는 비접촉식 중 비전센서인 레이저 다이오드와 CCD 카메라를 이용하여 CCD 카메라를 거친 영상을 처리하여 용접선을 추적하고 용접을 하도록 하고 있다. 레이저 다이오드를 용접모재와 일정 각도를 가지도록 조사하게 되면 모재표면의 형상에 따라 반사되는 굴곡면이 달라지게 되는데 이 형상이 CCD 카메라를 통해 입력되고, 이 입력된 화상을 이미지 보드와 프로그램을 통하여 분석을 하고, 얻어진 용접선의 화상의 좌표 값을 토대로 로봇을 이동시킴으로써 용접을 하도록 하고 있다. 용접은 실시간으로 이루어짐으로써 생산성 향상에 크게 기여할 수 있다. 또한 모재에 따라 굴곡이 다른 1차원 평면의 용접인 경우는 약간의 프로그램 수정으로 대부분 추적 가능하다는 것을 확인할 수 있었다.

• 한국의학물리학회지:의학물리
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• 제25권2호
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• pp.65-71
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• 2014

A Varian Portal Dosimetry system was compared to an isocentrically mounted MapCHECK 2 diode array for volumetric modulated arc therapy (VMAT) QA. A Varian TrueBeam STx with an aS-1000 digital imaging panel was used to acquire VMAT QA images for 13 plans using four photon energies (6, 8, 10 and 15 MV). The EPID-based QA images were compared to the Portal Dose Image Prediction calculated in the Varian Eclipse treatment planning system (TPS). An isocentrically mounted Sun Nuclear MapCHECK 2 diode array with 5 cm water-equivalent buildup was also used for the VMAT QAs and the measurements were compared to a composite dose plane from the Eclipse TPS. A ${\gamma}$ test was implemented in the Sun Nuclear Patient software with 10% threshold and absolute comparison at 1%/1 mm (dose difference/distance-to-agreement), 2%/2 mm, and 3%/3 mm criteria for both QA methods. The two-tailed paired Student's t-test was employed to analyze the statistical significance at 95% confidence level. The average ${\gamma}$ passing rates were greater than 95% at 3%/3 mm using both methods for all four energies. The differences in the average passing rates between the two methods were within 1.7% and 1.6% of each other when analyzed at 2%/2 mm and 3%/3 mm, respectively. The EPID passing rates were somewhat better than the MapCHECK 2 when analyzed at 1%/1 mm; the difference was lower for 8 MV and 10 MV. However, the differences were not statistically significant for all criteria and energies (p-values >0.05). The EPID-based QA showed large off-axis over-response and dependence of ${\gamma}$ passing rate on energy, while the MapCHECK 2 was susceptible to the MLC tongue-and-groove effect. The two fluence-based QA techniques can be an alternative tool of VMAT QA to each other, if the limitations of each QA method (mechanical sag, detector response, and detector alignment) are carefully considered.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.320-323
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• 2002

This paper presents a new generation of system for pressure vessel and shipbuilding. Typical pressure vessel and ship building weld joint preparations are either traditional V, butt, fillet grooves or have narrow or semi narrow gap profiles. The fillet and U groove are prevalently used in heavy industries and shipbuilding to melt and join the parts. Since the wall thickness can be up to 6" or greater, welds must be made in many layers, each layer containing several passes. However, the welding time for the conventional processes such as SAW(Submerged Arc Welding) and FCAW(Flux Cored Arc Welding) can be many hours. Although SAW and FCAW are normally a mechanized process, pressure vessel and ship structures welding up to now have usually been controlled by a full time operator. The operator has typically been responsible for positioning each individual weld run, for setting weld process parameters, for maintaining flux and wire levels, for removing slag and so on. The aim of the system is to develop a high speed welding system with multitorch for increasing the production speed on the line and to remove the need for the operator so that the system can run automatically for the complete multi-torch multi-layer weld. To achieve this, a laser vision sensor, a rotating torch and an image processing algorithm have been made. Also, the multitorch welding system can be applicable for the fine grained steel because of the high welding speed and lower heat input compare to a conventional welding process.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2001년도 춘계종합학술대회
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• pp.460-464
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• 2001

최근, 아크용접을 하는데 있어서 보다 균일한 용접상태와 용접품질의 향상 및 동일시간에 보다 많은 용접을 함으로써 생산성 향상을 위해 로봇의 이용이 점차로 증가하고 있다. 로봇용접의 과정 중 실제 용접을 실시하기 위해 로봇을 움직이기 이전에 용접할 부위의 검출이 선행되어야 하고, 그 검출방법에 있어서 크게 접촉식과 비접촉식으로 대별된다. 본 논문에서는 비접촉식 중 영상처리센서인 레이저 다이오드와 CCD 카메라를 이용하여 CCD 카메라를 거친 영상을 처리하여 용접선을 추적하고 용접을 하도록 하고 있다. 레이저 다이오드를 용접모재와 어떤 각도를 가지도록 조사하게 되면 모재표면의 형상에 따라 반사되는 굴곡면이 달라지게 되는데 이 형상이 CCD 카메라를 통해 입력되고, 이 입력된 화상을 이미지 보드와 프로그램을 통하여 분석을 하고, 얻어진 용접선의 화상의 좌표 값을 토대로 로봇을 이동시킴으로써 용접을 하도록 하고 있다. 용접은 실시간으로 이루어짐으로써 생산성 향상에 크게 기여할 수 있다. 또한 모재에 따라 굴곡이 다른 1차원 평면의 용접인 경우는 약간의 프로그램 수정으로 대부분 추적 가능하다.

• Journal of Welding and Joining
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• 제24권5호
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• pp.49-56
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• 2006

For laser welding in shipbuilding industry, gap bridging capability is one of the most important characteristics to achieve the high productivity and good weld quality. Recently, laser-GMA hybrid welding process is regarded as a distinctive method to overcome the tight gap tolerance with improving the productivity. In this study, the influence of process parameters on the bead formation was experimentally analyzed and the relationship between the process parameters and geometric imperfections was investigated. It was revealed that undercut, excessive weld metal, excessive penetration and incompletely filled groove were the major geometric imperfections. The optimized wire feeding and arc pressure were necessary to ensure the gap bridging ability. The approach to select the process parameters was conducted for butt welding with up to 2mm joint gap, in which the sound weld beads were generated without changing the welding speed.

• Journal of Welding and Joining
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• 제27권1호
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• pp.95-101
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• 2009

In case of manufacturing the high quality welds or pipeline, the full penetration weld has to be made along the weld joint. Thus the root pass welding is very important and has to be selected carefully. In this study, an experimental method for the selection of optimal welding condition was proposed in the root pass welding which was done along the V-grooved butt weld joint. This method uses the response surface analysis in which the width and height of back bead were chosen as the quality variables of the weld. The overall desirability function, which is the combined desirability function for the two quality variables, was used as the objective function for getting the optimal welding condition. In the experiments, the target values of the back bead width and the height are 6mm and zero respectively for the V-grooved butt weld joint of 8mm thickness mild steel. The optimal welding conditions could predict the back bead profile(bead width and height) as 6.003mm and -0.003mm. From a series of welding test, it was revealed that a uniform and full penetration weld bead can be obtained by adopting the optimal welding condition which was determined according to the method proposed.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.189-192
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• 2006

The purpose of this study is to evaluate the welding distortion at the channel I butt SA weldment. In order to do it, the heat input model for the weldment was defined as combined heat source with the surface heat flux of gaussian mode and volume heat source uniformly distributed within weld groove on the basis of comparing the shapes of molten pool and temperature distribution obtained by FEA and experiment. The arc efficiency of SA welding for 2 dimensional FE analysis was determined as 0.85. The results of welding distortions at the weldment obtained by FEA and heat input conditions proposed have a good agreement with those obtained by experiment. Based on the results, it was suggested that the proper heat input model should be required to evaluate the welding distortion for weldment.