• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1996년도 특별강연 및 추계학술발표 개요집
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• pp.102-104
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• 1996

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1999년도 특별강연 및 추계학술발표대회 개요집
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• pp.146-149
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• 1999

To develope the high speed gas cutting tip, consists of 3 pieces, supersonic axisymmetric jets issuing from various kinds of nozzles with a throat diameter of a few milimeters were experimentally investigated. The nozzle inlet pressure was varied from 4 to 8 kgf/$\textrm{cm}^2$. The parameters in nozzle design were throat diameter, throat length, taper angle, outlet diameter. The total pressure variation was measured by the pilot tube, 0.5mm outer diameter, along the center of the free stream jet. Also color Shilieren system was used to visualize the flowfield.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.88-93
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• 2008

Weld overlay is one of the residual stress mitigation method which arrest crack. An overlay weld sued in this manner is termed a preemptive weld overlay(PWOL). PWOL was good for distribution of residual stress of dissimilar metal weld(DMW) by previous research. Because range of overlay welding is wide relatively, residual stress distribution on PWR is affected by welding sequence. In order to examine the effect of welding sequence, PWOL was applied to a specific DMW of KORI nuclear power plant by finite element analysis method. As a result, the welding direction that from nozzle to pipe is better good for residual stress distribution on PWR.

• 한국레이저가공학회지
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• 제2권3호
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• pp.11-18
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• 1999

This paper describes the weldability of carbon steel and stainless steel using 5㎾ $CO_2$ laser system with nearly multi-mode beam and a parabolic focusing mirror. In the laser welding of steels, major welding parameters are focal point, travel speed, beam power, shield gas and gap tolerance, etc.. Two kinds of gases(Ar, He) were used as a assist gas and supplied through the external nozzle. It is very important for optimum condition to remove plasma plume which absorbs laser beam and to obtain deep penetration and sound weld bead. Bead-on-plate welding tests were carried out for the experiments. Penetration data were obtained with various welding parameters and the effects of welding parameters were discussed. Butt welding tests were performed with various conditions. Only the optimum laser parameters assured good weld quality As a result of this study, We achieve the fundamental weldabilities using a high power $CO_2$ laser for carbon steel and stainless steel.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 추계학술발표대회 개요집
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• pp.73-75
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• 2004

The purpose of this study is to optimize Nd:YAG laser welding parameters to seaz a Rf source into a Ti micro capsule. Ti tube ends can be sealed as some length of ぉbe end is melted and coalesced. The exact control of the melted length is the most important to get sound sealing. The Nozzle type, tube rotating speed, tilt angle, focal position, pumping voltage, pulse frequency and pulse width were selected as the Nd:YAG laser welding Parameters. These Parameters were optimized by the Taguchi experimental method using 115 orthogonal array. Appearance and cross section of the seated tube ends were examined by SEM.

• 대한기계학회논문집A
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• 제36권6호
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• pp.599-608
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• 2012

일체형 원자로의 안전주입 노즐 이종금속 용접부의 잔류응력에 대한 레이저 피닝의 효과를 고찰하기 위해 상용 프로그램인 ABAQUS를 이용하여 implicit 동적 유한요소 해석을 통해 연구를 수행하였다. implicit 동적 유한요소 해석은 기존의 실험 결과와의 비교에 따르면 레이저 피닝을 통한 잔류응력 이완에 대해 타당하다고 확인된다. 한편 내부 보수용접이 수행된 이종금속 용접부에 대해 해석이 수행되며 그 결과는 축방향 및 원환 잔류응력 모두 내부 보수용접에 기인하여 노즐의 내표면에서 인장임을 나타낸다. 또한 용접 잔류응력 이완에 대한 최대 충격 압력, 압력 지속 시간, 스폿 직경 및 피닝 방향과 같은 여러 변수의 효과를 고찰하기 위해 변수 해석 또한 수행하였다. 결과적으로, 레이저 피닝은 내표면 근처 영역의 잔류응력을 주로 이완시키는 예방정비 효과가 있음을 확인하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.90-95
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• 2004

In this study, we proposed new method to mitigate tensile welding residual stress for preventing PWSCC in CRDM nozzle. Residual stress analysis using finite element method is performed to confirm benefit of the new method. In case of applying existing method, tensile axial residual stress decrease by about 28% and tensile hoop residual stress decrease by about 33%. In case of applying the new method, tensile axial residual stress decrease by about 32% and tensile hoop residual stress decrease by about 43%. Therefore, we conclude the new proposed method is more effective to prevent PWSCC than existing method.

• Nuclear Engineering and Technology
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• 제51권3호
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• pp.776-783
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• 2019

Laser welding is usually a more effective method than electron-beam one since a vacuum chamber is not required. It is important for joining Zr-1%Nb (E110) alloy in a manufacturing process of nuclear fuel rods. In the present work, effect of energy parameters of pulsed laser welding on properties of butt joints of sheets with a thickness of 0.5 mm is investigated. The most efficient combination has been found (8-11 J pulse energy, 10-14 ms pulse duration, 780-810 W peak pulse power, 3 Hz pulse frequency, 1.12 mm/s welding speed). The results show that ultimate strength under static loading can not be used as a quality criterion for zirconium alloys welds. Increased shielding gas flow rate does not allow to protect weld metal totally and contributes to defect formation without using special nozzles. Several types of imperfections of the welds have been found, but the major problem is branching microcracks on the surface of the welds. It is difficult to identify the cause of their appearance without additional research on improving the welding zone protection (gas composition and flow rate as well as nozzle configuration) and studying the hydrogen content in the welds.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.85-87
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• 2008

DMWs are common feature of the PWR in the welded connections between carbon steel and stainless steel piping. The nickel-based weld metal, Alloy 82/182, is used for welding the dissimilar metals and is known to be susceptible to PWSCC. A round-robin program has been implemented to benchmark the numerical simulation of the transient temperature and weld residual stresses in the DMWs. To solve the round-robin problem related to Pressurizer Safety & Relief nozzle, the thermal elasto-plastic analysis is performed in the DMW by using the FEM. The welding includes both the DMW of the nozzle to safe-end and the SMW of the safe-end and piping. Major results of the analyses are discussed: The axial and circumferential residual stresses are found to be -88MPa(225MPa) and -38MPa(293MPa) on the inner surface of the DMW; where the values in parenthesis are the residual stresses after the DMW. Thermo-mechanical interaction by the SMW has a significant effect on the residual stress fields in the DMW.

• 한국산학기술학회논문지
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• 제10권11호
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• pp.3074-3079
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• 2009

지속적인 경제 발전과 인구증가로 인하여 에너지 소비가 급증하게 되면서 에너지의 효율적인 사용이 필요하다. 특히 에너지 손실이 많은 건물의 창호에 단열성능이 좋은 고효율 진공유리 사용이 절실한데 아직 가격 및 성능등의 문제로 보급화가 이루어지지 않고 있다. 따라서, 본 연구에서는 저가의 진공유리 개발을 위한 유리 용접용 토치를 설계 및 제작하였다. 연료는 고밀도 열원인 수소-산소 혼합가스를 사용하였고 주로 토치 형상, 노즐 직경, 노즐 배치 등의 최적화를 수행하였다. 끝으로 개발된 토치를 이용하여 두 장의 유리용접을 성공적으로 수행함으로써 저가의 진공유리 개발 가능성을 확인하였다.