• Proceedings of the KSME Conference
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• 2002.08a
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• pp.671-674
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• 2002

Pressure compensating temperature control valve(TCV) is one of the important control devices, which is used to maintain the constant temperature of working fluid in power and chemical plants. The ratio of cylinder hole diameters of inlet and outlet is the main design parameters of TCV. So this needs to be investigated to improve the function of control of temperature and void fraction. In this study, numerical analysis is carried out with various ratios of cylinder hole diameters of the inlet and outlet in the TCV. Especial1y, the distribution of the static pressure Is investigated to calculate the new coefficient($C_{\upsilon}$) and resistance coefficient(K). The governing equations are derived from making using of three-dimensional Naver-Stokes equations with standard $k-{\varepsilon}$ turbulence model and SIMPLE algorithm. Using a commercial code, PHOENICS, pressure and flow fields in TCV are calculated with different inlet and outlet diameters of the cylinder hole for cold and hot water passages.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.10a
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• pp.37-42
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• 1997

This paper describes result of experiment of parameters affecting the micro hole drilling time, kind of assisting gas and it's pressure. The result reveals that parameter value of 0.08J, 20Hz, dwell time of 300 microseconds can be a good machining condition to make micro hole diameter range of 50-70${\mu}{\textrm}{m}$, Assistant gas such air, O2, Ar, N2 was adapted. Assistant gas of air makes heat affected zone enlarge due to burning of material, also it makes hole irregular and damage because of refusion stick to caused by chemical reaction with Al2O3 ceramic material. O2(99.9%) has good characteristic to get good drilling and smooth surface on pressure of 0.2kgf/$\textrm{cm}^2$, but it is expensive. Ar, N2 makes material burn and crack severely and proved to be an appropriate but, Ar was better than N2.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.5
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• pp.88-93
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• 2012

This paper describes the machinability of the sintered carbide and tool-die steel(STD-11) by electric discharge drilling with various tubular electrodes which have multi-holes. Various types of electrode which have different diameters and materials are used with the application of continuous direct current and axial electrode feed. Inner part of electrodes are inserted with smaller tubes or Y-channel or bar. In ED-Drilling, the dielectric flushed down the interior of the rotating tube electrode, in order to remove machining debris from the hole. As result of experiments, the bigger the diameter of the electrode is, the lower the material removal rate is. Machinability of copper electrode is higher than that of brass. In machining of sintered carbide, to use oil is better than distilled water as dielectric.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.181-182
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• 2006

When a water jet is injected on the body surface, the pressure and shear stress on the surface are important physical parameters in determining the body surface wash out and physical stimulus. We used the force plate in order to measure the surface average pressure for different nozzle types and distances between a nozzle and a plate. We used the nozzles with a hole dimeter of 1.8, 2.9, 3.2mm, and the shower heads with 10 holes (hole diameter, 1mm) and 20 holes (hole diameter, 1mm). The distances between a nozzle and a plate was 10, 20, 30, 40cm. The results showed that the surface forces were not affected by the distances between a nozzle and a plate. Further numerical studies will be performed to predict wall shear stress based on the measured pressure data.

• Journal of Mechanical Science and Technology
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• v.14 no.10
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• pp.1021-1027
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• 2000

In this study, fatigue tests were performed to examine the effects of micro drill hole on fatigue limit of as cast and austempered ductile cast iron (ADI) using the rotary bending fatigue tester. As results, micro drill holes ($diameter{\leq}0.4mm$) did not influence the fatigue limit of ADI, compared to annealed ductile cast iron; the critical defect size of crack initiation, in ADI was larger than as cast. If the ${\sqrt{area}}$ of micro drill hole and graphite nodule in ADI are comparable, crack initiates at the graphite nodule. When the ruggedness developes through austempering treatment process, microstructure on crack initiation at micro drill hole is tougher than that of as cast ductile cast iron.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.213-216
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• 2001

A micro hole punching system was developed and micro holes of 100m in diameter were successfully made on brass sheets of loom in thickness. A micro punch made of tungsten carbide was designed to withstand the punch load, considering the buckling and the bending moment due to possible misalignment error. The punch was fabricated by the grinding process with diamond wheel. The die was designed considering the punch load and fabricated by micro electrodischarge machining process. In this system the stripper is designed to guide punch tip to minimize the possible misalignment. The punch was installed on a vertical stepper and the die was mounted on an X-Y translation unit. The precision motion controller controlled all motions of the micro hole punching system. In this study technical difficulties and solutions in the micro hole punching process were also discussed.

• Laser Solutions
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• v.6 no.1
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• pp.9-16
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• 2003

Micromachining using the DPSS 3rd Harmonic Laser (355nm) has outstanding advantages as a UV source in comparison with Excimer lasers in various aspects such as maintenance cost, maskless machining, high repetition rate and so on. It also has the greater absorptivity of many materials in contrast to other IR sources. In this paper, the process for micro-drilling of blind hole in Cu/PI/Cu substrate with the DPSS UV laser and the scanning device is investigated by the experimental methods. It is known that there is a large gap between the ablation threshold of copper and that of PI. We use the Archimedes spiral path for the blind hole with different energy densities to ablate the different material. Finally, the blind via hole of diameter 100$\mu\textrm{m}$ and 50$\mu\textrm{m}$ was drilled.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.5
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• pp.7-12
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• 2017

It is assumed that the buckling and cutting conditions depending on the slenderness ratio will affect the machining quality of the rotary boring tool mounted on a milling machine. In this study, the boring cutter was designed and fabricated to precisely create the Ø30 hole. Through the performance evaluation, the accuracy of the hole according to the slenderness ratio and cutting conditions was analyzed, and the following conclusions were obtained. The higher the RPM, the smaller the change in the working diameter, and the smaller the hole. Next, the smaller the slenderness ratio, the smaller the change in straightness due to the change in cutting conditions. Finally, the slenderness ratio also affects the tendency for changes in the concentricity. The larger the slenderness ratio, the more sensitive the concentricity to changes in cutting conditions.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1052-1058
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• 2003

The possibility of micro/nano machining through electro-chemical process is discussed in this research. Electro-chemical dissolution region is localized within 1 ${\mu}m$ by applying ultra short pulses with tens of nanosecond duration. The effects of voltage, pulse duration, and pulse frequency on the localization distance are investigated. Localization distance can be manipulated by controlling the voltage and pulse duration, and various hole shapes are produced including stepped holes and taper free hole. High quality micro-hole with 8 ${\mu}m$ diameter with 20 ${\mu}m$ depth and micro-groove with 9 ${\mu}m$ width with 10 ${\mu}m$ depth are machined on 304 stainless steel.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.2
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• pp.80-86
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• 2002

A fuel injection system has an important role in the performance and emission gas in a diesel engine. In this paper, an experimental study has been performed to verify the effect of the performance and the emission gas with the factors such as diameters of an injection nozzle hole, diameters of an injection pipe, and injection timing in the fuel injection system. We have obtained the results that the fuel consumption ratio is reduced and NOx concentration is increased as the smaller diameter of injection nozz1e hole, the smaller diameter of injection pipe, and more advanced injection timing. They show that optimizing the factors of fuel injection system is significant to enhance the performance of the engine system and consumption ratio of fuel, smoke, and NOx.