• 한국기계가공학회지
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• 제18권5호
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• pp.103-109
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• 2019

The pressure reducing valve for water is controlled by the load of the compression spring and the force of the fluid acting on the diaphragm of the stem. Repeated upward and downward reciprocation of the pressure-reducing valve stem damages the diaphragm, resulting in leakage. In this study, we designed a stem without a diaphragm and adjusted the stiffness of the compressing spring. In order to select the spring stiffness, springs offering a stiffness of -20%, -10%, 0%, and 10% with respect to the stiffness of the compression spring attached to the existing pressure reducing valve stiffness. A prototype for the pressure reducing valve was fabricated and the pressure change was evaluated for the target static pressure (6 bar) by testing the pressure characteristics after mounting the modified stem and each compression spring. Evaluation of the pressure characteristics was carried out using ASSE 1003 and KS B 6153. In addition, the flow rates were compared by internal flow analysis of the conventional pressure reducing valve and the pressure reducing valve using the modified stems, and the flow analysis was performed using Solidworks flow simulation 2018. The spring stiffness was constantly discharged at the target static pressure of 3.793 kgf/mm, and the flow rate was increased by about 15% compared with the conventional pressure reducing valve.

• 한국압력기기공학회 논문집
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• 제12권1호
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• pp.115-125
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• 2016

The prototype SFR has currently been under design by KAERI. The size of its major components is much larger than that of APR1400 and high temperature materials are applied for it. The increased size of components and those specific materials effect on material procurement, manufacturing process and fabrication facilities. The manufacturing methods are studied for Reactor Vessel/Guard Vessel, Control Rod Drive Mechanism, Heat Exchanger, Primary Pump, Reactor Vessel Internals, Steam Generator and In-Vessel Transfer Machine. The proper manufacturing methods are suggested for each component including side forging technology for ultra large forgings of Reactor Vessel to minimize the weld seams on which In-service Inspection should be conducted.

• 대한인간공학회지
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• 제21권2호
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• pp.71-86
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• 2002

This study's purpose is to gain basic data for the factory automation of manufacturing custom-made girdles. For this study , obese women in their 30s and 40s was experimented through direct measuring and by the 3D scanner, by means of which the proportions of the subject's body was measured. Based upon the results of this experiment, individually designed girdles were made. In order to gain the basic data for the factory automation of manufacturing custom-made girdles, the patterns and the clothing pressure and the feeling of wearing such girdles were analyzed. This study can be summarized as follows: The material properties and the designs of existing functional girdles in the market were studied thoroughly, and the subject were required to wear those existing girdles. On the basis of this result, the experimental girdles were designed and produced which could serve well the subject's intension. The experimental girdles were of the basic long-type in order to apply to all sorts of girdles, and they were produced according to the style and pattern of the existing grading system. The second experiment was conducted by applying the subject's body measurements. Due to the elasticity of the material, in girdles the smaller measurements were to be used in this second experiment were: 80% of waist size, 84% of the hip and 85% of the thigh. To determine the length of the girdles, the same measurements were applied. The test results of the feeling of wearing the experimental girdles showed that the second, custom-made experimental girdles were better. According to the test results of the clothing pressure, the second experimental girdles(custom-made girdles) marked the higher pressure than the first on every part of the body, especially on the hips and thighs. Thus, it can be said that the second experimental girdles are better than the first in lifting up the hips. It is expected that the design methods developed in this study can be utilized as basic resources for the factory automation system of manufacturing custom-made girdles.

• 한국생산제조학회지
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• 제21권4호
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• pp.563-569
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• 2012

In the semiconductor and display device production processes, the handling of sensitive objects needs new carrying technology. Floating carrying motion is a practical alternative solution for non-contact handling of parts and substrates. This paper presents a study of through paths inside the air pressure pick-up head to generate the floating motion. The air motion by conceptual designed paths inside the head gradually develops positive pressure and vacuum between narrow objects. Positive pressure occurs through the head tip before discharging outside of the head. Negative pressure is developed by evacuating the inside head bottom as result of the radial flow connecting the vertical through-holes. The numerical analysis was done to figure out the stable levitation caused by the two acting forces between surfaces. In comparing with the standard case that the levitation gap gets 0.7-0.9 mm, it confirms the suggested head characteristics to show floating capacity in accordance with the head size, number of through-hole, and locations of through-hole in succession of conceptual design for a prototype.

• 한국기계가공학회지
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• 제10권4호
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• pp.64-69
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• 2011

Magnesium alloy has been known as lightweight material in automobile and electronic industry with aluminum alloy, titanium alloy and plastic material. Friction welding is useful to join different kinds of metals and nonferrous metals they are difficult to be joined by such as gas welding, resistance welding and electronic beam welding. In this study, friction welding was performed to investigate optimization process of Mg alloy with a 20mm diameter solid bar. For that, the orthogonal array $(L_{9}(3^{4}))$ was used that contained four factors and each factor had three levels. Control factors were heating pressure, heating time, upsetting pressure and upsetting time. Also tensile tests were carried out to measure mechanical properties for welded conditions. The levels of heating pressure and upsetting pressure used were 15, 25, 35MPa, and 30, 50, 70MPa, respectively. In addition those of heating time and upsetting time were 0.5, 1, 1.5 sec and 3, 4, 5 sec., respectively, rotating speed of 2000rpm. From the experimental results, optimization condition was estimated as follows; heating pressure=35MPa, upsetting pressure=70MPa, heating time=1.5sec, upsetting time=3sec.

• 한국생산제조학회지
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• 제9권1호
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• pp.88-95
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• 2000

In this paper, an expansion-resonator type pulsation attenuator is proposed to absorb and attenuate flow an pressure ripple with high frequencies generated from hydraulic control systems. The basic principle of a pulsation attenuator proposed here is applied to propagation, reflection, absorption of pressure waves at the cross section of discontinuity and resonance in the pipeline. It has advantage of the compact size and high degree fo freedom for installation in hydraulic systems. The design scheme based on distributed parameter pipeline system with dissipative viscous compressible model is developed. To investigate the reduction of flow and pressure ripple with high frequencies produced by swash plate type axial piston pump, two kinds of attenuators are manufactured. It is experimently confirmed that the spectral intensity of flow and pressure ripple with high frequencies from the pump are reduced up to about 20$^{\circ}$~30dB by using attenuators proposed here. The calculated results were in good agreement with the measured values. From there sults of this study, it is shown that an expansion-resonator type pulsation attenuator is effective in a wide frequency ranges to attenuate the flow and pressure ripple from hydraulic components.

• 한국기계가공학회지
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• 제17권4호
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• pp.150-159
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• 2018

The present research deals with a finite element analysis and fatigue evaluation of a steam separator of a high-pressure evaporator for the Heat Recovery Steam Generator (HRSG). The fatigue during the expected life of the HRSG was evaluated according to the ASME Boiler and Pressure Vessel Code Section VIII Division 2 (ASME Code). First, based on the eight transient operating conditions prescribed for the HRSG, temperature distribution of the steam separator was analyzed by a transient thermal analysis. Results of the thermal analysis were used as a thermal load for the structural analysis and used to determine the mean cycle temperature. Next, a structural analysis for the transient conditions was carried out with the thermal load, steam pressure, and nozzle load. The maximum stress location was found to be the riser nozzle bore, and hence fatigue was evaluated at that location, as per ASME Code. As a result, the cumulative usage factor was calculated as 0.00072 (much less than 1). In conclusion, the steam separator was found to be safe from fatigue failure during the expected life.

• 한국정밀공학회지
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• 제34권4호
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• pp.247-251
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• 2017

Titanium alloy has been widely used in the aerospace industry because of its high strength and good corrosion resistance. During cutting, the low thermal conductivity and high chemical reactivity of titanium generate a high cutting temperature and accelerates tool wear. To improve cutting tool life, cryogenic machining by using a liquid nitrogen (LN2) jet is suggested. In cryogenic jet cooling, evaporation of LN2 in the tank and transfer tube could cause pressure fluctuation and change the cooling rate. In this work, cooling uniformity is investigated in terms of liquid nitrogen jet pressure in cryogenic jet cooling during titanium alloy turning. Fluctuation of jet spraying pressure causes tool temperature to fluctuate. It is possible to suppress the fluctuation of the jet pressure and improve cooling by using a phase separator. Measuring tool temperature shows that consistent LN2 jet pressure improves cryogenic cooling uniformity.

• 한국생산제조학회지
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• 제22권3_1spc호
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• pp.551-557
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• 2013

The heat transfer performance and pressure drop characteristics of brazed-plate heat exchangers with 20 and 30 plates were experimentally measured and analyzed in this study. The mass flow rates of the heat exchangers with 20 and 30 plates were fixed at 0.6 and 0.9 kg/s for the low temperature side, respectively. The mass flow rate for the high temperature side was controlled from 0.2 kg/s to 1.2 kg/s. The inlet temperatures for the high and low temperature sides were $10^{\circ}C$ and $7^{\circ}C$, respectively. The heat transfer characteristics were not influenced by the number of plates. The pressure drop at the heat exchanger with 30 plates was slightly higher than that with 20 plates. The values calculated from the correlations based on gasket plate heat exchangers were compared with the experimental results. It was found that the predicted Nusselt numbers for the gasket plate heat exchangers were about 5% to 20% lower than the measured Nusselt numbers for the brazed plate heat exchangers. However, a pressure drop comparison showed that the calculated pressure drops at the gasket plate heat exchangers were less than half of the measured pressure drops at the brazed plate heat exchangers.

• 한국생산제조학회지
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• 제21권1호
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• pp.1-6
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• 2012

This paper presents a stress safety of a composite pressure cylinder for a hydrogen gas vehicle. The composite pressure cylinder in which is composed of an aluminum liner and carbon fiber wound layers contains 104 liter hydrogen gas, and is compressed by a filling pressure of 70 MPa. The FEM computed results are analyzed based on the US DOT-CFFC basic requirement for a hydrogen gas cylinder and KS B ISO specification. The FEM results indicate that the stress, 255.2 MPa of an aluminum liner is sufficiently low compared with that of 272 MPa, which is 95% level of a yield stress for aluminum. Also, the composite layers in which are wound on the surface of an aluminum cylinder are safe because the stress ratios from 3.46 to 3.57 in hoop and helical directions are above 2.4 for a minimum safety level. The proposed composite pressure cylinder wound by carbon fibers is useful for 70 MPa hydrogen gas vehicles.