• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.803-807
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• 2000

This paper deals wi th the establishment of the method of non-contact surface roughness measurement by developed system. One of the most Important factor of determinating quality of a produced manufacture is surface roughness The tendency of manufacturing method is changing from small amount manufactures / high-volume production to large amount manufactures / low volume production, and the study of reducing time for surface roughness measurement has been actively investigated The non-contact surface roughness method by using laser which is different from contact method has been only used to the polished surface, so new surface roughness measurement method was adopted by virtue of Fraunhofer diffraction in the periodic surface for on-the-machine. in this paper, we establish the method of non-contact surface roughness measurement which can reduce measuring time in the periodic surface

• Tribology and Lubricants
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• v.16 no.6
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• pp.455-460
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• 2000

The real area of contacts, average film thickness, mean real pressure, and mean hydrodynamic pressure are investigated numerically in this study, especially for the parallel thrust bearing. Model surface is generated numerically with given autocorrelation function and some surface profile parameters. Then the average Reynolds equation contained flow factors and contact factor is applied to predict the effects of surface roughness in mixed lubrication regimes. In this equation, flow factors are defined as correction terms to smooth out high frequency surface roughness and contact factor is introduced to relieve from obtaining the average film thickness. Therefore the computation time to obtain barh h can be reduced.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.827-831
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• 1997

Conductive veramic matrix composite(CMC) workpiece of TiC 33%/Al /sab 2/O /sab 3/ 66% Y /sab 2/ O /sab 3/ was machined by die sinking electrical discharge machining(EDM) according to different pulse duration and suty factor for reverse polarity of electrode. Material removal rate(MRR) was examined by process under various operating conditions. The surface morphology was evaluated by surface roughness values and scanning electron microscopy(SEM) research. The more MRR was obtained according to increase pulse duration and duty factor. Also the maximum surface roughness(Rmax) of EDMed surface was slightly changed with increased pulse duration and duty factor. The SEM photographs of EDMed surface showed wide recast wide recast distribution region of melting materials in purse duration 0.130(ms) than 0.048(ms).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.3-7
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• 1996

Metal Matrix Composite(MMC) material of 30% SiC particulate based on A1 matrix was machined by drilling and Electrical Discharge Machining (EDM) processes. When drilling process was executed, surface fracture due to brittle property near the bottom was found. It was also found the possiblity of difficult shape of EDM process for MMC material, but few the research about basic EDM characteristics. Material Removal Rate(MRR) was examined for different conditions and the surface morphology was evaluated by roughness values and Scanning Electron Microscopy(SEM) research. The higher the current is, the more MRR was obtained but the higher MRR was showed around 0.45 duty factor. The average roughness of EDMed surface was slightly changed with increased pulse current and increases with duty factor. The SEM photographs of EDMed surface showed recast region after melting.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.5
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• pp.587-592
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• 1999

The combined effects of radius ratio and roughness pitch ratio on the turbulent fluid flow characteristics of the fully developed flow in the annullar tubes with rib-roughened core walls were determined for Reynolds number ranging from 12,000 to 66,000. To understand the underlying physical phenomena responsible for friction factor enhancement, measurements of velocity profiles and zero shear stress and maximum velocity positions were combined to propose the friction factor correlation. Friction factors were found to be a function of the roughness pitch ratio and radius ratio.

• Journal of Welding and Joining
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• v.19 no.3
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• pp.298-304
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• 2001

Turbine blade is subject to force of three types ; the torsional force by torsional mount, the centrifugal force by the rotation of rotor and the cyclic bending force by steam pressure. The cyclic bending force was a main factor on fatigue strength. SEM fractography in root of turbine blade showed micro-clack width was not dependent on stress intensity factor range. Especially, fatigue did not exist on SEM photograph in root of turbine blade. To clear out the fracture mechanism of turbine blade, nanofractography was needed on 3-dimensional crack initiation and crack growth with high magnification. Fatigue striation partially existed on AFM photograph in root of turbine blade. Therefore, to find a fracture mechanism of the torsion-mounted blade in nuclear power plant, the relation between stress intensity factor range and surface roughness measured by AFM was estimated, and then the load amplitude ΔP applied to turbine blade was predicted exactly by root mean square roughness.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.170-177
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• 2001

Turbine blade is subject to torsional load by torsion-mount, centrifugal load by rotation of rotor and repeated bending load by steam pressure. Turbine with partially cracked blade has normal working condition at initial repair time but vibratory working condition at middle repair time due to crack growth. Finite element analysis on turbine blade indicates that repeated bending load out of all loads is the most important factor on fatigue strength of turbine blade. Therefore, this study shows root mean square roughness has linear relation with stress intensity factor range in 12% Cr steel and can predict loading condition of fractured turbine blade.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.2
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• pp.181-187
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• 2009

In this study, a runoff hydrograph and runoff volume were calculated by using the kinetic wave theory for small urban watersheds based on the concept of low impact development(LID), and the effective imperviousness was estimated based on these calculations. The degree of sensitivity of the effective imperviousness of small watersheds to the impervious to pervious area ratio, infiltration capability, watershed slope, roughness coefficient and surface storage depth was then analyzed. From this analysis, the following conclusions were obtained: The effective imperviousness and paved area reduction factor decreased as the infiltration capability of pervious area increased. As the slope of watersheds becomes sharper, the effective imperviousness and the paved area reduction factor display an increasing trend. As the roughness coefficient of impervious areas increases, the effective imperviousness and the paved area reduction factor tend to increase. As the storage depth increases, the effective imperviousness and the paved area reduction factor show an upward trend, but the increase is minimal. Under the conditions of this study, it was found that the effective imperviousness is most sensitive to watershed slope, followed by infiltration capability and roughness coefficient, which affect the sensitivity of the effective imperviousness at a similar level, and the storage depth was found to have little influence on the effective imperviousness.

• Journal of the korean Society of Automotive Engineers
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• v.9 no.5
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• pp.57-65
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• 1987

The surface rolling method which is one of the plastic deformation processes increases the surface roughness with reduction of diameter and hardness. In this study, three NACHI 6000 ZZ bearing were used for surface rolling tool on a mild steel The following results have been obtained with the mild steel. 1) The load is major factor in getting fine surface roughness of roller finishing after grinding The optimal surface roughness of SS41 steel can be obtained at the contact pressure of 210 kgf/cm$^{2}$. 2) At the contact pressure range of 200kgf/cm$^{2}$-210kgf/cm$^{2}$ for optimal surface roughness, The surface hardness increased to Hv200-Hv240 from Hv 125 before surface rolling. 3) Within the diameter variation of 13 .mu.m the surface roughness and the surface hardness were increased, but out of variation of 14.mu.m. The surface roughness become worse and the surface hardness was increased.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1205-1210
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• 2005

The behavior of rock mass and solute(e.g. groundwater, radioactivity) flow in fractured rock can be directly influenced by joint roughness. The characteristics of joint roughness is also a main factor for the rock classification(e.g. RMR, Q system) which is usually used in tunnel design. Nevertheless, most of JRC estimation has been carried out only by the examination with the naked eye. This JRC estimation has a lack of objectivity because each investigator judges JRC by his subjective opinion. Therefore, it will be desirable that the assessment of JRC is performed by a numerical analysis which can give a quantitative value corresponding to the characteristics of a roughness curve. Meanwhile, roughness curves for joint surfaces which are observed in drill cores have been obtained only along linear profiles. Although roughness curves are measured in the same joint surface, they can frequently show diverse aspects in a standpoint of roughness characteristics. If roughness curves can be measured along the elliptical circumferences of joint surfaces from core scanning images or Televiewer images, they will certainly be more comprehensive than those measured along linear profiles for roughness characteristics of joint surfaces. This study is focus on dealing with (1) extracting automatically roughness curves from core scan image or Televiewer image, (2) improving the accuracy of quantitative assessment of JRC using fractal dimension concept.