• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1390-1393
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• 2003

Work factor approach is conveniently used in metal fracture mechanics to determine fracture toughness from a single fracture test. In this work, we investigated the applicability of the work factor approach in order to determine fracture toughness of thick graphite/epoxy composites in the hydrostatic pressure environment from a single fracture test. The effect of hydrostatic pressure on the elastic work factor was studied, The stacking sequence used was multi-directional, [0$^{\circ}$/${\pm}$45$^{\circ}$/90$^{\circ}$]. The hydrostatic pressures applied were 0.1 MPa, 100 MPa, 200 MPa, and 300 MPa. The results showed that the elastic work factor was not affected by the hydrostatic pressure, The elastic work factor decreased in a linear fashion with crack length.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1087-1091
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• 2004

In this study, the ultra precision centerless grinder for ferrule grinding was designed. The centerless grinder is composed of the high damping concrete bed, grinding wheel spindle unit, regulating wheel spindle unit, feeding table and dressing unit. For a newly developed centerless grinder, hydrostatic system with high precision feeding and high stiffness was proposed. The grinding and regulating wheel spindle units were composed of hydrostatic spindle and feeding table was hydrostatic table. The prototype of hydrostatic table was manufactured and tested.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.406-409
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• 2004

In this study, we investigated compressive characteristics of seawater-absorbed carbon-epoxy composite under hydrostatic pressure environment. The hydrostatic pressures applied were 0.1 MPa, 100 MPa, 200 MPa, and 270 MPa. The results showed that the compressive elastic modulus increased about 10 % as the hydrostatic pressure increased from 0.1 MPa to 200 MPa. The modulus increased 2.3 % more as the pressure increased to 270 MPa. Fracture strength and fracture strain increased with pressure in a linear fashion. Fracture strength increased 28 % and fracture strain increased 8.5 % as the hydrostatic pressure increased from 0.1 MPa to 270 MPa.

• Journal of Power System Engineering
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• v.15 no.5
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• pp.5-9
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• 2011

The hydraulic piston using a hydrostatic bearing has been used widely due to its satisfying performance at very high pressurized circumstance and relative higher power density in comparison to conventional one. For high pressurization, enhanced efficiency and long durability of the hydraulic piston, the design of hydrostatic bearing is at issue, which is installed between piston shoe and swash plate. The performance of the hydrostatic bearing is influenced significantly by the assembly of the piston shoe consisting of circular land and recess. In this study, to estimate the performance of the hydrostatic bearing, the characteristics for lubrication of the assembly of the piston shoe were investigated by measuring a leakage rate of hydraulic fluid under an experimental condition, where a rotating velocity of the piston, hydraulic pressure and temperature of the hydraulic fluid were changed systematically. In addition, a film thickness of the hydraulic fluid on the piston shoe was measured and compared to theoretical one.

• International Journal of Precision Engineering and Manufacturing
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• v.4 no.2
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• pp.57-63
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• 2003

A new method using a transfer function was proposed in the previous paper for analyzing motion errors of hydrostatic tables. The calculated motion errors by the new method, named as the transfer (unction method (TFM), were compared with the results by the conventional multi pad method, and the validity of the proposed method was theoretically verified. In this paper, the relationship between rail form error and motion errors of a hydrostatic table is examined theoretically in order to comprehand so-called 'the averaging effect of an oil film', and the characteristics of the motion errors in a hydrostatic table is tested. The tested hydrostatic table has three single-side pads in the vertical direction and three pairs of double-sides pads in the horizontal direction. The motion errors are tested for three rails which have different form errors. The experimental results are compared with the theoretical results calculated by the TFM, and both results show good agreement. From the results, it is shown that the TFM is very effective to analyze the motion errors of hydrostatic tables.

• The International Journal of Costume Culture
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• v.4 no.3
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• pp.241-248
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• 2001

Re water resistance of shell fabrics intended for we in outdoor apparel was measured using three different standard test methods, ASTM D 751, hydrostatic resistance, procedure A(Mullen test -- with and without a fabric support) and Procedure B (Hydrostatic head test). A database of information on their water resistance performance was created. The data collected with different methods were correlated and the advantages and disadvantages of each method were compared. The Mullen test with a support appears to give higher and more favorable water resistance values on shell fabrics preventing fabric rupture during the test. The hydrostatic head test gave lower hydrostatic pressure values than those measured on the two Mullen tests. The Mullen test is recommended for testing the water resistance of fabrics that high a relatively high water resistance because the Mullen tester applies a wide range of pressure. The hydrostatic head test is recommended for testing the fabrics that have relatively low water resistance. The area of the fabric sample that is in contact with the water is smaller in the Mullen test, so higher pressure levels can be reached and more samples should probably be tested to get a representative value for each fabric types. Furthermore, the hydrostatic head test was deemed more repeatable than the Mullen tests in his study.

• Transactions of The Korea Fluid Power Systems Society
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• v.7 no.3
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• pp.7-12
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• 2010

In the case of hydraulic piston motor, hydrostatic bearing is designed to be adapted the hydrostatic bearing for the relative lubrication in the structural design. It's available to make it highly efficient and that's why it's widely used. The thing which largely influence the high pressure, the high efficiency, and the life is the hydrostatic bearing between a shoe and a swash plate. In this study, with the most general "hydrostatic bearing shoe" that has one recess as the subject of this research, I designed and made the 4 kind of piston shoe that have different orifice diameter each other, and studied the features of the hydrostatic bearing by observing the change of the leakage flow rate, the torque and the volumetric efficiency through experiments on the changes of the pressure & the speed of the revolution. As a result, the bigger diameter of the orifice, the less torque. And with an increase of the orifice diameter under the high pressure, the leakage flow rate decreased remarkably. Also it was observed the leakage flow rate increased linearly according to the increase of the supply pressure.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.1
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• pp.96-100
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• 2011

The hydrostatic bearings have a relatively small run-out comparing to its shape error by fluid film effect in hydrostatic state as like pneumatic bearing and have a high stiffness, load capacity and damping characteristics. As there is no maintenance and semipermanent in these bearing type, it has been usually adopted as main spindle bearing for grinding machine. In this thesis, to develop hydrostatic bearing for high speed spindle, the cooler setting temperature, bearing clearance and nozzle pressure of belt-driven hydrostatic bearing are investigated. The bearing temperature is decreased, as the cooler setting temperature is lower, nozzle pressure is higher and bearing clearance is wider. The front temperature of bearing is nearly $8^{\circ}C$ higher than the rear one up to 13,000 rpm of spindle revolution. The thermal deflection of X-axis is ${\pm}16\;{\mu}m$ in range of 12,000 rpm-13,000 rpm. Therefore, it is conformed that the built-in motor hydrostatic bearing can be used to high speed spindle.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.712-717
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• 2000

Hydrostatic bearings have been applied to high precision machine tools and instruments, because the bearing has high stiffness, high damping and excellent straightness. This paper treats a procedure for designing a high precision press with linear hydrostatic bearings.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.438-441
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• 2004

In this study, we investigated compressive characteristics of seawater-absorbed carbon-epoxy composite under hydrostatic pressure environment. The hydrostatic pressures applied were 0.1 MPa, 100 MPa, 200 MPa, and 270 MPa. The results showed that the compressive elastic modulus increased about 10 ％ as the hydrostatic pressure increased from 0.1 MPa to 200 MPa. The modulus increased 2.3 ％ more as the pressure increased to 270 MPa. Fracture strength and fracture strain increased with pressure in a linear fashion. Fracture strength increased 28 ％ and fracture strain increased 8.5 ％ as the hydrostatic pressure increased from 0.1 MPa to 270 MPa.