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변철웅 대한용접접합학회 1994 대한용접·접합학회지 Vol.12 No.2
In comparison to the conventional brazing, laser welding of ceramics has advantages of direct bonding without filler material, which causes the thermal stress due to the differences of thermal expansion coefficients. In pulse-mode, laser welding of dispersion ceramic having high thermal resistance is possible at relatively low preheating temperature of $1300^{\circ}C$ In CW-mode, alumina can be welded at high preheating temperature $1500^{\circ}C$ under the condition of low feed rate of 500 mm/min, respectively. Further studies on developing mechanism of pores in the bead during laser welding of ceramics is required.
홍석관,강정진,변철웅,Hong, Seok-Kwan,Kang, Jeong-Jin,Byun, Cheol-Woong 한국레이저가공학회 2008 한국레이저가공학회지 Vol.11 No.3
This study is aimed to analyse the laser glass bonding process numerically. Due to the viscoelastic behaviour of glass, the extremely large deformation of the frit seal is resulted continuously over the transition temperature, so that the thermal boundary condition be changed in the entire calculation process. The commercial FEM algorithm is restrictively able to remesh the large geometrical boundary shape and to adapt the boundary conditions simultaneously. According to our manual adaptation of increasing the laser line intensity to 700 mW/mm, it is possible to estimate the thermal glass bonding process under the fracture stress in principle. But it should be studied further in the case of high laser line intensity.
이상우,신대영,변철웅,Lee, Sang-Woo,Shin, Dae-Young,Byun, Cheol-Woong 한국전산구조공학회 2007 한국전산구조공학회논문집 Vol.20 No.5
소화시스템에 사용되는 고압의 소화가스 저장용기에는 저장용기의 파손을 막아주는 안전밸브가 있다. 이러한 안전밸브의 내부에는 원형 박판의 파열 판이 들어 있는데, 저장용기의 내압이 위험수준에 도달하면 파열 판이 파손하여 내압을 배출하는 역할을 한다. 안전밸브의 설계인자는 파열 판의 두께, 안전밸브의 유로 직경, 플라스틱 패킹 링의 내부 직경 그리고 파열 판을 고정하는 볼트 안쪽의 필렛 반경이 있다. 이중에서 파열 판의 두께는 0.2mm로 고정을 하였다. 요인배치법을 사용하여 주효과를 결정하였고 회귀방정식을 유도하였다. 이러한 회귀방정식은 추후 안전밸브의 설계에 있어서 기초 설계 자료로서 활용할 수 있도록 실험 결과와 비교하여 검증하였다. 검증실험 및 회귀방정식에 의한 결과의 오차는 약 $2{\sim}5%$ 정도인 것을 확인하였다. 그리고 반응표면법을 사용하여 기밀테스트 압력인 25MPa에서 파열할 수 있는 안전밸브의 최적 모델을 결정하였다. High pressure storage of the agent gas in fire suppression system was composed of tank, main valve and safety valve, which prevents the fracture of the high pressure storage. The safety valve has circular thin plate as fracture plate that was destroyed over fracture pressure. When inner pressure of the storage is reached the fracture pressure, the safety valve discharges gas and degrades simultaneously the inner pressure of the storage. There are design variables such as flow path diameter, inner diameter of the plastic packing ring, thickness of plate and fillet radius. In this variables, thickness of plate is set to be a value of 0.2mm. The main effect of variables on the inner pressure, has been decided using factorial design and statistical analysis. Therefore, the relation of variables are expressed by regression equation. It is disclosed results that the difference of fracture pressures between the equation and experiment has $2{\sim}5%$. Finally, using response surface method, the optimal design of the safety valve could be decided with safety pressure of 25MPa, where the fracture occurs on circular thin plate.
양진석(Yang Jin Seok),변철웅(Byun Cheol Woong),신대영(Shin Dae Young) 한국생산제조학회 2007 한국공작기계학회 춘계학술대회논문집 Vol.2007 No.-
Optical absorptance of the plastic material is a critical parameter in the quality of weld seam during the laser plastic welding process, and frequent measurements of this value are required because material properties of the plastics can fluctuate greatly due to the change of the processing parameters such as compound mix and injection molding process variables. Absorptance is usually estimated indirectly by measuring the transmittance and reflectance of the material. Accurate measurement devices based on several principles, spectroscopic apparatus, integrating sphere, calorimetry method, for instance, have been developed and some are commercially available in the market. But these are not adequate for the regular use in the production field. In this work, portable equipment is developed for measuring absorptance with reasonable accuracy, convenience and angle dependent measuring capability. Measuring principle and instrumentation are described, and measurement results of PMMA and ABS plastic materials are presented.