• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.413-414
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• 2008

Abstract should be in English. The leaning angle optimization of turbine blade using the genetic algorithm was conducted in this paper. The calculation CFD technique was based upon the Diagonalized Alternating Directional Implicit scheme(DADI) with algebraic turbulencemodeling. The leaning angle of VKI turbine blade was represented using B-spline curve. The control points are the design variable. Genetic algorithm was taken into account as an optimization tool. The objective was to minimize the total pressure loss. The optimized final geometry shows the better aerodynamic performance compared with the initial turbine blade.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.4
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• pp.50-55
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• 2008

CNC wire bending machines are used in industries to make a type variety of wire products such as long links. The machines have a long arm device to rotate in order to remove forming errors by flexibility of wire. Generally, the machines which constructed servo motors in the arm have the rotating range of the arm under 360 degree because the servo motors connect with fixed control devices on frame by many cables. The rotating angle under 360 degree limits working speed and forming geometry. Therefore this study developed a gear train to drive a parts in arm and to be independent on arm rotation movement. The developed gear train can transfer four movements to four components in arm and is consists parallel of four pairs of satellite gear trains. This study constructed the CNC wire bending machine with the developed gear train and verified that the gear train could drive internal components independently on arm rotation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.8
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• pp.1259-1265
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• 2003

We present a new post-fabrication frequency tuning method for laterally driven electrostatic microresonators using a DC-biased electrostatic comb array of linearly varied finger-length. The electrostatic tuning force and the equivalent stiffness, adjusted by the DC-biased tuning-comb array, have been formulated as functions of geometry and DC tuning voltage. A set of frequency-turnable microresonators has been designed and fabricated by 4-mask surface-micromachining process. The resonant frequency of the microfabricated microresonator has been measured for a varying tuning voltage at the reduced pressure of 1 torr. The maximum 3.3% reduction of the resonant frequency is achieved at the tuning voltage increase of 20V.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1419-1424
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• 2003

Impact analysis of TFT-LCD module is very complicated because the structure is assisted with thin, small and non-uniform geometry. Especially, finite element modeling is more difficult and need time-consuming efforts. In this study, we developed LCD Impact Analysis System (LIAS) for the purpose of reducing the analysis time without accuracy reduction. This system contains pre-meshing data, material database, shock condition, auto-reporting etc. PATRAN and DYNA3D is used for meshing and solving. Previously, we performed impact test and reviewed the accuracy of analysis results. Simply we can control design parameters, the procedure such as meshing, running and reporting which are partially auto-prepared. By adopting proposed system, it is expected to achieve efficient impact analysis of LCD module.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.235.2-235.2
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• 2014

Plasma hardly grows in low pressure because of lack of collision. Especially, in extremely low pressure like 1 mTorr, the experiment scale is far larger than mean free path therefore plasma is hardly generated in such low pressure. But low pressure plasma has useful properties like low damage or fine sputtering process because it has typically low electron density. In here, thermal electron is used to make breakdown in low pressure easily and cylindrical geometry is used to help discharge easily. And we changed magnetic field strength to control electron density or temperature. In low pressure, density and temperature behavior is very interesting so its characteristics are examined here.

• The KSFM Journal of Fluid Machinery
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• v.8 no.4 s.31
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• pp.7-13
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• 2005

Although the globe is the most typical valve to control high pressure drop in piping system, it is very hard to figure out the characteristics of flow field in the globe valve caused by its complex geometry, So there is very few studies to find out flow characteristics of globe valve. In this study numerical analysis for flow field in the globe valve is carried out using the FLUENT code which is commercial CFD program. Pressure drop through the globe valve is also measured to verify the results come from numerical analysis. Comparing experiment with numerical analysis, two results are very close to each other.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2002.07a
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• pp.133-155
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• 2002

1. Quasicrystalline powders shows exotic physical and mechanical p properties 2. Applications: structural application: strengthening particles for composites C Coating application: wear resistance, low friction coefficient 3. For thermal spaying: material loss during process should be c considered to control chemical composition of deposit 4. Friction coefficient is strongly dependent on contact geometry F Friction coefficient from pin on plate: 0.1-0.2 Friction coe야icient from flat on plate: about 0.46. 5. Quasicrystalline materials show lower friction coefficient but higher w wear rate than corresponding values of $Cr_20_3$ coated layer. 6. Amorphous coating seems to be promising

• Journal of the Korean Society for Precision Engineering
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• v.26 no.4
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• pp.55-63
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• 2009

This paper reports on the theoretical and experimental study of the pressure ripples in a pressure unbalanced type vane pump which have widespread use in industry. Because they can infinitely vary the volume of the fluid pumped in the system by a control. Pressure ripples occur due to the flow ripples induced by geometry of side plate, leakage flow, reverse flow from the outlet volume produced by pressure difference between pumping chamber and outlet volume when the pumping chamber connected with the outlet volume. In this paper, we measured the pressure variation of a pumping chamber, reaction force on a cam ring, the mathematical model for analyzing the pressure ripples which included vane detachment and fluid inertia effects in notch area has been presented, and was applied to predict the level and the wave form of the pressure ripples according to operating conditions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.301-304
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• 2004

Friction welding was used to weld the turbine wheel and shaft and have a good welding quality. Friction welding was conducted an the two dissimilar material, Nimonic 80A and SNCrW. The control of friction welding process parameter such as flywheel energy, interface temperature, amount of upset have an effect on the mechanical properties of the welded joint. FE simulation can be a useful tool to optimize the weld geometry and process parameters. Flash shape and thickness weld is consistent with the simulated results. Process analysis was performed by the commercial code DEFORM 2D. Mechanical property of weld joints was evaluated by microstructure, chemical component, tensile, impact, hardness test so on.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.10
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• pp.200-207
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• 2001

Burrs farmed in drilling are classified into three types, no burr, burrs with cap, teared burr. To control burr size in drilling, the second type burrs with cap are to be formed because it is small and uniform. It is necessary to understand the mechanism of cap formation to derive the burr formation into second type burr with cap. In several materials. second type burrs are formed in drilling by changing cutting conditions. It is observed that cap is formed as a result of the plastic deformation along the outside of exit hope. According to the tension behavior of the material in concentrated region between hole and drill outside edge, the geometry of burr with cap is determined. Simplified 2D FEM analysis shows good prediction for burr formation.