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초내열합금 wide-gap 브레이징부의 미세조직 및 기계적 성질 변화에 미치는 첨가금속분말의 영향
김용환,권숙인,변재원,이원식,Kim Y. H.,Kwun S. I.,Byeon J. W.,Lee W. S. 한국재료학회 2005 한국재료학회지 Vol.15 No.6
The effect of IN738 additive powder on microstructure and mechanical properties of the wide-gap region brazed with BNi-3 filler metal powder was investigated. The wide-gap brazing was conducted in a vacuum of $2\times10^{-5}torr\;at\;1200^{\circ}C$ with various powder mixing ratios of additive to filler powders. The microstructures of the wide-gap brazed region were analyzed by SEM and AES. The region brazed with only BNi-3 filler metal powder had a microstructure consisted of proeutectic, binary eutectic and ternary eutectic structure, while that brazed with a mixture of IN738 additive powder and BNi-3 filler metal powder had a microstructure consisted of IN738 additive powder, binary eutectic of $Ni_3B-Ni$ solid solution and (Cr, W)B. The fracture strength of the wide-gap brazed region was about 680 MPa regardless of the additive powder mixing ratios. Cracks were initiated at the (Cr, W)B and binary eutectic of $Ni_3B-Ni$ solid solution, and propagated through them in the wide-gap brazed region, which lowered the fracture strength of the region.
Mg 합금의 온간 Hole Flange 성형에 대한 수치적 연구
김용환(Y.H.Kim),이현영(H.Y.Lee) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
Warm hole-flanging process for Mg alloy with considering heat transfer among die, blank, blank holder and punch was simulated by finit element method(FEM) to investigate the improvement of hole flangeability and temperature distribution of AZ31 Mg alloy sheet. In this model, both die and blank holder were heated to blank temperature while the punch was kept at room temperature(20℃). The temperature of the blank if the range of 200~400℃ and the room temperature. The simulation results were compared to those obtained from the same model without considering heat transfer. Through the study, the effect of various process variable on the flangeavbility of Mg alloy will be investigated.
적응적 요소 재구성을 이용한 타이어 트레드 성형의 유한 요소 해석
김용환(Y.H.Kim),이현영(H.Y.Lee),류민영(M.Y.Lyu) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
Automobile tire has very complicated shape and is composed of rubber, steel cord and ply cord. Tread pattern of tire is very essential for the basic characteristics of tire, such as braking, acceleration and comfortableness. Tire components such as tread, sidewall, and apex are prepared by forcing uncured rubber compound through an extruder to shape during curing process. Because of its complexity of shape, adaptive mesh refinement was used for the analysis of tire tread. Effects of forming variables were evaluated.