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부도체 방향복사면이 있는 무한 정사각관의 전도-복사열전달
변기홍,임문혁,Byun, Ki-Hong,Im, Moon-Hyuk 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.5
The effects of a directionally emitting and reflecting dielectric surface on the wall heat flux and medium temperature distribution are studied. The system is an infinite square duct enclosing an absorbing and emitting medium. The emissivity and reflectivity of opaque and gray wall vary with direction. Combined effect of conductive and radiative heat transfer is analyzed using finite difference and the direct discrete-ordinates method. The parameters under study are conduction to radiation parameter, optical depth, refractive index ratio. The results with directional and diffuse properties deviate each other when the conduction to radiation parameter is less than around 0.01. The wall heat flux differs fur optical thickness less than around 0.1. However, the medium temperature profiles differ for optical thickness greater than around 1. Deviations from diffuse property calculations are larger for hot wall with directional property than cold wall with directional property. As n increases from 1.5, the trend changes are observed fur refractive index ratio about n=6.10
〈기술논문〉 레진이 피복된 카렌더기의 롤 크라운양(roll crown) 설계에 관한 연구
서홍석(Hong Seok Seo),조순옥(Soon Ok Jo),박대규(Dae Kyu Park),임문혁(Moon Hyuk Im),전두환(Du Hwan Chun) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
A major design parameter of a calender roll for maintaining even contact pressure in the direction of the axis, in fabric processing, is the amount of crown on the roller. The amount of crown is based on experience in the production facility. The contact pressure is affected by the deflection of the roll as well as the deformation caused by the contact. In this study, an experimental apparatus for measuring the contact pressure and the amount of deflection was constructed. Then measurements such as contact width, contact pressure, and deflection caused by the amount of crown and fluctuation of the load were taken. An ANSYS based model was used to determine the amount of crown resulting in an uniform distribution of contact load. Comparison of the results of the model and the experiments were surprisingly close. Through this study, the relationship between the load and amount of crown for obtaining the optimal contact pressure was clarified.
최해운(Hae Woon Choi),신현명(Hyun Myung Shin),임문혁(Moon Hyuk Im) 대한기계학회 2008 大韓機械學會論文集A Vol.32 No.11
An application of innovative laser+GMA hybrid welding process is presented for reducing bead humping defects in high speed welding and increasing side wall fusion in narrow groove welding without torch or wire oscillation. In this hybrid process, the laser heat input is applied adjacent to the weld pool at a relatively low power density to produce a wider, flatter weld bead. In bead on plate in sheet metal gauges, the hybrid process was able to produce hump-free welds from 70ipm (~1780㎜/min) to over 150ipm (~3810㎜/min) of the travel speed compared to the un-assisted GMAW process. A square-butt joint in 15mm A572 Gr50 steel welds was investigated. A square butt joint with a gap of 3.2㎜ was filled with 6 passes. Liquid Nitrogen calorimetry and innovative CO₂ laser reflective optics were also developed to demonstrate the concept of hybrid welding.