• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.185-190
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• 2003

Synchronizer ring performance is strictly required in order to extend manual transmission oil drain interval. Zn type additive, which is used as dispersant and anti-wear additive instead of SP additives in manual transmission oil, is applied to improve Synchronizing function and durability. But only Zn type additive is not suitable for high torque transmission because it has not good extreme pressure characteristics. We research on the synchronizer friction and extreme pressure properties in according to change additive types. As a result, it was found that the use of non-active extreme pressure and friction modifier additives has benefit in the improvement of synchronizer friction characteristics and durability.

• Journal of the Korean Society for Precision Engineering
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• v.5 no.2
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• pp.33-42
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• 1988

In a large scale oil hydraulic system having repeatedly operated actuator, such as a large scale forging press, pressure surges often due to the recombination of oil column in a return line attached to the downstream side of a directional control valve. Expecially, the pressure surges appear very severe ones at a certain valve operating frequency. These pressure surges restrict the operating frequency of the hydraulic system. But related reports on the above mentioned phenomenon are rarely to be found. In this study, therefore, the authors investigate the exact reason why such severe pressure surges occur at a certain range of valve operating frequency. The study is performed by experiment and numerical computation on the relationship between pressure surges and valve operating frequency.

• Journal of Mechanical Science and Technology
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• v.19 no.12
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• pp.2179-2186
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• 2005

The lubrication modes of line contact between the vane and the camring in an oil hydraulic vane pump have been investigated. First, variations of the radial acting force of a vane were calculated from previously measured results of the dynamic internal pressure in four chambers surrounding a vane. Next, distinctions of the lubrication modes were made using Hooke's chart, which represents an improvement over Johnson's chart. Finally, the influence of boundary conditions in the lubrication region on fluid film lubrication was examined by calculating film pressure distributions. The results show that the lubrication modes of the vane tip are a rigid-variable viscosity region. This region discharges pressure higher than 7 MPa, and exerts a great influence on oil film pressure in the large arc section due to the Piezo-viscous effect.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1989.11a
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• pp.94-99
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• 1989

This paper analyzes file stiffness, damping coefficient, friction force and flow coefficient of externally pressurized oil journal beating, including the effect of journal rotation according to the Sommerfeld number. This paper assumed that the oil in the whole pocket has constant pressure, and that the oil in the whole bearing region has constant viscosity, temperature and density. Reynolds equation is derived from Nuvier - Stokes equation and continuity equation. And solved bearing pressure by ADI method for whole bearing region and fitted with out flow rate of pocket region. The model for numerical simulation is hydro - static oil journal bearing for high-speed, high-accuracy lathe spindle.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.111-119
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• 2002

• Tribology and Lubricants
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• v.22 no.1
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• pp.47-52
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• 2006

It is very important to control pressure and flow rate distribution on each component of engine lubrication network. Sometimes many kinds of orifice are used to control flow rate in the hydraulic lubrication field. In this study orifices were adopted on the lubrication network to control oil flow rate distribution. And unsteady transient flow network analysis was carried out to find out the effects of orifices on the engine oil circuit system.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.2
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• pp.141-149
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• 2009

The oil pan is an important factor for the noise behavior of the engine system. In this paper a new Magnesium oil pan was designed and analyzed to replace the current Aluminium oil pan. Dynamic stiffness and sound pressure level of the newly designed Mg oil pan were compared with the AI oil pan using the finite element method. NVH characteristics of the Mg oil pan is slightly insufficient when we changed the material of the oil pan from Al to Mg without modifying the design. Some design modifications of the Mg oil pan resulted in equal or superior characteristics compared to the Al oil pan. New ribs were added to stiffen the structure of the Mg oil pan. Thickness of thin plate area was increased to reduce the radiated noise. Through the changes of shape, higher dynamic stiffness than the current Al oil pan were achieved. Results of frequency response analysis show that we can reduce the sound pressure level of the oil pan if we increase the thickness of the thin plate area. It is shown that the new Mg oil pan could reduce the weight of the engine system and improve NVH quality of an automobile.

• Geomechanics and Engineering
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• v.7 no.4
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• pp.403-430
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• 2014

Shale gas formations exhibit strong mechanical and strength anisotropies. Thus, it is necessary to study the effect of anisotropy on the hydraulic fracture initiation pressure. The calculation model for the in-situ stress of the bedding formation is improved according to the effective stress theory. An analytical model of the stresses around wellbore in shale gas reservoirs, in consideration of stratum dip direction, dip angle, and in-situ stress azimuth, has been built. Besides, this work established a calculation model for the stress around the perforation holes. In combination with the tensile failure criterion, a prediction model for the hydraulic fracture initiation pressure in the shale gas reservoirs is put forward. The error between the prediction result and the measured value for the shale gas reservoir in the southern Sichuan Province is only 3.5%. Specifically, effects of factors including elasticity modulus, Poisson's ratio, in-situ stress ratio, tensile strength, perforation angle (the angle between perforation direction and the maximum principal stress) of anisotropic formations on hydraulic fracture initiation pressure have been investigated. The perforation angle has the largest effect on the fracture initiation pressure, followed by the in-situ stress ratio, ratio of tensile strength to pore pressure, and the anisotropy ratio of elasticity moduli as the last. The effect of the anisotropy ratio of the Poisson's ratio on the fracture initiation pressure can be ignored. This study provides a reference for the hydraulic fracturing design in shale gas wells.

• Journal of Mechanical Science and Technology
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• v.18 no.6
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• pp.1019-1025
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• 2004

Pressure variation is one of the major sources on noise emission in the axial type oil piston pumps. Therefore, it is necessary that the pressure variation characteristics of the oil hydraulic piston pumps be clarified to reduce the pump noise. Pressure variations in a cylinder at the discharge region and the pump noise were simultaneously measured with discharge pressures and rotational speeds during the pump working. To investigate the effects of the pre-compression and the V-notch in the valve plate, we used the three types of valve plates. In this research, it is clear that the pressure variation characteristics of axial type oil piston pumps is deeply related to the pre-compression and to the V-notch design in valve plate. Therefore, we could reduce the pump noise by using the appropriate pre-compression angle and the notch design that are between the suction port and the discharge port in valve plate.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.405-406
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• 2002

The main subject of this paper is analyzing the patterns of maximum oil film pressure and the minimum oil film thickness under various pre-conditions of geometric shape as functions of bearing groove and proceeding oil hole in the connecting rod bearing. As the major analytical tool, elastohydrodynamic lubrication analysis has been applied and two-intertwined results of maximum oil film pressure and minimum oil film thickness have been compared and analyzed using EXCITE program. From computed results, the optimal lubrication conditions as geometric shape of bearing groove and the proceeding oil hole have been investigated. This may be useful for the bearing designer as a firm reference.