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신현명(Hyun Myung Shin),이영민(Young Min Lee),최해운(Hae Woon Choi) 한국생산제조학회 2012 한국생산제조학회지 Vol.21 No.3
A femtosecond laser with 775nm central wavelength and 150 fs of temporal pulse width was used for multi layered glass cutting applications. Ultrashort pulse was effectively used for clean glass cutting with 50μm depth and minimum cutting width. Laser beam was split to two stages and focused on the top surfaces of each layer. Ablation threshold of used glass was measured to be 2.59J/㎠. In experiments, 200mW laser power and 1mm/s scanning speed was used for preliminary experiment. Air gap was the major defect occurring parameter and laser power was less sensitive to glass cutting in the experiment. The maximum cutting speed was measured to be 60mm/min with 2kHz, however, Maximum 3m/min cutting speed can be achievable with a commercially available laser with 100kHz.
히트파이프 히트싱크에서 평판 휜-관으로 구성된 공기유동 냉각채널의 대류 열전달 특성에 관한 수치해석
김성훈,신현명,김철주,Kim Sung-Hoon,Shin Hyun-Myung,Kim Chul-Ju 한국마린엔지니어링학회 2005 한국마린엔지니어링학회지 Vol.29 No.8
A study on convective cooling characteristics has been done in the channels with heat pipes and associated Plane fins Analysis with FLUENT V5.0 lies its Purpose on the possible enhancement of heat transfer capability between an existing three in-line arrayed heatpipes and an extending four in-line arrayed heatpipes with increasing channel width. Numerical analysis is limited to the laminar flow in an isolated flow channel by employing cyclic boundary conditions for calculation purposes. Friction factors for three and four in-line arrayed heatpipes are compared with experimental results. In addition, temperature behavior at the plate fin for the three in-line arrayed heatpipes is compared with experiment. Friction factors and overall channel heat transfer coefficients (and/or Nusselt numbers) are presented as a function of Reynolds number. An increase of number of heatpipes and channel width reults in a decrease of the friction factor and doesn't not result in an increase of heat transfer performance. However. considering the 25$\%$ increase of heat load accompanies with maximum 8$^{\circ}C$ rise of average temperature of heat pipes, the four in-line array with the increase of channel width of heat pipe heat sink can be considered appropriate.
발전용 증기터빈 밸브 케이싱의 유한요소해석과 주조결함 평가 방법
이부윤,김원진,신현명,Lee Boo-Youn,Kim Won-Jin,Shin Hyun-Myung 한국마린엔지니어링학회 2005 한국마린엔지니어링학회지 Vol.29 No.5
Stresses of main stop valve and control valve casings for the steam turbines of power plants are analyzed by the finite element method. The stress intensity is obtained to check the results on the basis of the design criteria of ASME boiler and pressure vessel code. To verify accuracy of the finite element analysis. analyzed stresses are compared with those measured during the hydrostatic pressure test. Stress category drawings. which play an important role in evaluating casting defects, are produced from the analysis results, and important points in casting of the valve casings are discussed in terms of the stress category.
논문 : 하이브리드 용접방식을 이용한 박판 및 후판용접공정
최해운(Hae Woon Choi),신현명(Hyun Myung Shin),임문혁(Moon Hyuk Im) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
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 at almost triple the travel speed of the un-assisted GMAW process. A square-butt joint in 15㎜ 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.
펨토초레이저를 이용한 알루미늄 성형다이의 미세가공에 관한 연구
최해운(Hae Woon Choi),신현명(Hyun Myung Shin) Korean Society for Precision Engineering 2009 한국정밀공학회지 Vol.26 No.5
Interface friction in blanking dies, cold forging and extrusion of aluminum alloys is a major cause of inefficient process. This paper describes an investigation of femtosecond laser texturing for reduction of interface friction on sliding surfaces in forming process. Femtosecond direct writing technology was used to fabricate a laser micro-machined die and to create microgroove patterns with varying size and density on metal forming dies. A systematic approach to find the optimum parameters and computer simulation comparison of friction coefficients are provided to study the relation of friction coefficients and die profiles. In metal forming tests, the effectiveness of various laser?machined patterns for enhancing interface lubrication is determined.
이병수(Byoungsoo Lee),신현명(Hyun Myung Shin),허만대(Man-Dae Hur) 한국자동차공학회 2004 한국 자동차공학회논문집 Vol.12 No.4
Three models with various degree-of-freedom for a manual transmission clutch full-size tester have been developed and the models' reliability and accuracy have been verified using the measured data. A simulation study has also been conducted to understand dynamic behavior of the tester. The model for this simulation study includes clutch disk friction and damper dynamics. The developed model is very accurate in terms of maximum torque exerted on the clutch, slip duration and the vibration response except a slight difference compared to the measured data. In a history graph of the clutch torque, the maximum toque response from simulation is flat but the measured is sunken with a noticeable curvature. This phenomenon is found to be irrelevant to the dynamics of the full-size tester but is originated from the characteristics of the clutch itself. Thus, the full-size tester has been proven to be a reliable tester for clutch's power and torque transmission capability. To obtain a better understanding of clutch's characteristics and relationship between full-size tester and other testing methodologies, future research directions have been suggested.
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.