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고속 추진체용 Alloy 718 노즐 단조품의 전자빔 용접성 평가
이채훈(C. H. Lee),김정한(J. H. Kim),홍재근(J. K. Hong),염종택(J. T. Yeom),윤종원(J. W. Yoon),박노광(N. K. Park) 한국소성·가공학회 2008 소성가공 : 한국소성가공학회지 Vol.17 No.7
In this study, mechanical properties of Alloy 718 welded after forgings for jet propulsion component was investigated. Hot-forged and machined work-pieces(230mm×70mm×15mm) which have different grain sizes are welded by electron beam welding technique. After welding, the components were solution heat-treated and aged. Samples were sectioned to analyze the microstructural evolution and formation of micro-crack. It was found that HAZ grain boundary liquation crack generally initiates in the coarse grains rather than the fine grains. Needle-like phases with high Nb contents were found at the outer part near the base metal. Vickers hardness and tensile tests were carried out at room temperature and at 649℃. The tensile properties of electron beam welding specimens exhibited around 100MPa and 10% decrease in strength and elongation, respectively.
한승철(Seung Cheol Han),이민근(M.G.Lee),윤종원(J.W.Yoon),한상민(S.M.Han),서용석(Y.S.Suh),강기주(Ki-Ju Kang) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
A periodic cellular metal (PCM) has both load supporting performance and thermal management properties. A few years ago, a new technique for fabricating PCM, known as Wire-woven Bulk Kagome (WBK), was introduced. The WBK has been proved that it has high strength-per-weight. In this work, the buckling responses of two types of WBKcored sandwich panels subjected to in-plane compression were investigated. For both types, the peak loads were governed by macro plastic buckling. Low shear modulus and strength of the WBK core substantially influenced the buckling behaviors of the sandwich panels before and after their peaks. Classical theories, experimental and numerical results were presented. The effects of several factors were analyzed.
Cell size와 방향에 따른 WBK 심재의 압축거동
이정우(Jeong Woo Lee),이민근(Min Geun Lee),강기주(Ki-Ju Kang),윤종원(J.W.Yoon),한상민(S.M.Han),서용석(Y.S.Suh) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
This paper studies the compressive properties of mild steel WBK (Wire-woven Bulk Kagome) cores. To determine stiffness, the average displacements of WBK were measured using the two clip gages. The effects of orientation and cell size on the equivalent strength and equivalent Young’s modulus of WBK for given external dimensions of the specimens are evaluated. The equivalent peak strengths of the WBK cores in y and x-orientations were about 3/4 and 1/2 of that in z-orientation, respectively, and the equivalent Young’s moduli in y and x-orientations were about 5/6 of that in z-orientation.
샌드위치 판재의 굽힘 거동에 미치는 불연속 WBK 심재의 영향
김하라(H.R. Kim),이민근(M.G. Lee),윤종원(J.W. Yoon),한상민(S.M. Han),서용석(Y.S. Suh),강기주(K.J. Kang) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
The bending properties of sandwich panels with discontinuous WBK (Wire-woven Bulk Kagome) cores were investigated. Analytic solutions were derived, and the experimental and numerical results were presented. The analytic solutions provided good estimations of the failure mode, peak load, and bending stiffness in comparison with the experimental results. The strength and stiffness of sandwich panels with discontinuous WBK cores under bending load often substantially deteriorated depending on the gap width between the cores and on the detailed geometry near the gap. The analytic solutions successfully explained how the deterioration of the bending strength or stiffness could be minimized, when two separate sandwich panels or cores are to be joined.
6061 알루미늄 합금 Nd : YAG 레이저 용접의 기계적 성질에 관한 연구 YAG laser welded 6061 aluminum alloy
윤종원,이윤상,이문용,정병훈 한국레이저가공학회 2003 한국레이저가공학회지 Vol.6 No.2
6061 aluminum alloy sheets were I-square butt welded using a continuous wave Nd: YAG laser. Heat inputs were varied from 54.6 to 80 J/mm for butt welding using different sets of the laser power and the weld speed. I-square butt welds were also made with and without Ar shielding gas. The effect of Ar shielding gas and heat input on the mechanical properties and formability was investigated using Vickers hardness, transverse-weld tensile and bulge test. Porosity on the weld beads and sections and hot crack on the fracture surfaces of transverse-weld tensile test specimens were investigated using optical and scanning electron microscopy. The experimental results showed that mechanical properties and formability of 6061 aluminum alloy laser welds were degraded compared to those of base metal. Mechanical properties and formability of 6061 aluminum alloy laser welds were not substantially changed when Ar shielding gas was supplied or heat inputs were varied.
5052 알루미늄 합금 레이저 용접부의 기계적 성질에 관한 연구
윤종원,이윤상,이문용,정병훈 한국레이저가공학회 2003 한국레이저가공학회지 Vol.6 No.1
5052 aluminum alloy sheets of 2mm thickness were butt welded using a continuous wave Nd:YAG laser with and without Ar shielding gas. Vickers hardness, transverse-weld tensile and bulge tests were carried out to investigate the effect of Ar shielding gas on the mechanical properties and formability of laser welds. Porosity in the weld metals was investigated using an optical microscope. Mechanical properties and formability of 5052 aluminum alloy laser welds were degraded compared to those of base metal. However, those properties were improved due to the reduced size and number of porosity when Ar shielding gas was used.