• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.53-57
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• 1998

In order to investigate the effects of the variables during the stamping process upon the side wall curl behavior, experiments and finite element analyses were done using a 90 degree draw-bending test. The variables considered were the die radius, the forming speed, the restraint force, the lubrication and the sheet grade. The experiments and simulation conditions were selected according to the design of experiment (DOE) approach. The effects of the restraint force, the lubrication and the forming speed were the same for both high strength and mild steels, but the effects of the die radius on the side wall curl were dependent on the magnitude of the die radius and the sheet grade. A straight side wall was observed for both high strength and mild steels when the die radius was about 2∼3 times of the sheet thickness. It was recommended that the restraint force, the forming speed and the friction be increased in order to reduce the side wall curl.

• Journal of computational fluids engineering
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• v.18 no.2
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• pp.99-108
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• 2013

The standard drag force and virtual mass force, which exert to the primary flow direction, are generally considered in two-phase analysis computational codes. In this paper, the lift force, wall lubrication force, and turbulent dispersion force including turbulence models, which are essential for a computational multi-fluid dynamics model and play an important role in motion perpendicular to the primary flow direction, were introduced and verified with conceptual problems.

• Journal of the korean Society of Automotive Engineers
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• v.11 no.4
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• pp.35-42
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• 1989

The major purpose of this paper is a study on the effect of die profile radius on the formability of spring-type blankholder system in deep drawing process. By drawing the various materials, formability is studied by means of checking the drawing force, blankholding force variation, limiting drawing ratio and wall wrinkling phenomenon. As the die profile radius increases, the maximum drawing force and maximum blankholding force decrease regardless of lubrication condition. Because better lubrication induces blankholding force to rise, spring type blankholder system is better to protect flange wrinkling phenomenon than constant pressure type. And wall wrinkling phenomenon was not detected in experimental die radius range, so the Miyakawa's upper wrinkling limit is understimated in case of material tested.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.7
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• pp.1138-1145
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• 2003

In this paper, a study on the dynamic behavior and lubrication characteristics of a reciprocating compression mechanism used in small refrigeration compressor is performed. In the problem formulation of the compressor dynamics, the viscous frictional force between piston and cylinder wall is considered in order to determine the coupled dynamic behaviors of piston and crankshaft. The solutions of the equations of motion of the reciprocating mechanism along with the time dependent Reynolds equations for the lubricating film between piston and cylinder wall and oil films of the journal bearings are obtained simultaneously. The hydrodynamic forces of journal bearings are calculated using finite bearing model and Gumbel boundary condition. And, a Newton-Raphson procedure was employed in solving the nonlinear equations of piston and crankshaft. The results explored the effects of design parameters on the stability and lubrication characteristics of the compression mechanism.

• Tribology and Lubricants
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• v.30 no.2
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• pp.116-123
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• 2014

The objective of this study is to model and simulate the nonlinear lubrication performance of the sliding part between the piston and cylinder wall in a hydrostatic swash-plate-type axial piston pump. A numerical algorithm is developed that facilitates simultaneous calculation of the rotating body motion and fluid film pressure to observe the fluid film geometry and power loss. It is assumed that solid asperity contact, so-called mixed lubrication in this study, invariably occurs in the swash-plate-type axial piston pump, which produces a higher lateral moment on the pistons than other types of hydrostatic machines. Two comparative mixed lubrication models, rigid and elastic, are used to determine the reaction force and sliding friction. The rigid model does not allow any elastic deformation in the partial lubrication area. The patch shapes, reactive forces, and virtual local elastic deformation in the partial lubrication area are obtained in the elastic contact model using a simple Hertz contact theory. The calculation results show that a higher reaction force and friction loss are obtained in the rigid model, indicating that solid deformation is a significant factor on the lubrication characteristics of the reciprocating piston part.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.3
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• pp.94-104
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• 1994

In order to improve engine performance and its reliability it is very important to find the friction force between piston-ring assembly and cylinder wall in engine operating conditions. A new system was developed for the piston-ring assembly friction force measurement. This system had a relatively high fundamental frequency at 884 Hz and a fine resolution of 0.5N in friction force measurement. Comparing with existing floating liner systems this systems required small installation space and at the same time alleviated the system noise problem induced by the thrust and slap impulse forces.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.3
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• pp.56-64
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• 2000

A friction force measurement system using the floating liner method was developed to study the frictional behavior of piston rings. The measurement system was carefully designed to control the effect of the piston secondary motion and the temperature of cylinder wall and oil. The friction force between the barrel shaped piston ring and the cylinder liner, was measured under the condition of flooded oil supply. The measured friction forces were classified into five frictional modes with regard to the combination of predominant lubrication regimes(boundary, mixed and hydrodynamic lubrication) and stroke regions(midstroke and dead centers). The modes could be identified on the Stribeck diagram of the friction coefficients and the dimensionless number of ㎼/p, where the friction coefficients are evaluated at near the midstroke and dead centers.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1510-1519
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• 1994

It is important to understand the friction characteristics between piston-ring assembly and cylinder wall for the friction loss reduction as well as the solution of problem such as scuffing wear and oil consumption. A new system was developed for the piston-ring assembly friction force measurement. This system was applied to the friction force measurement to find its functional relationship with variables such as engine speed, oil viscosity, and engine load. The friction mean effective pressure(fmep) was found to have a linear relationship with$(\vpsilon{U})^{0.42}$ under motering and with$(\vpsilon{U})^{0.45}$ under firing operations, where $\vpsilon$ is the kinematic oil viscosity and U is mean piston speed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.356-363
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• 2001

Piston seal is a device designed to prevent leakage in split connecctions or between relatively moving part. Contact force, critical pressure at which extrusion occurs, leakage rate, fluid film thickness and friction force have been analyzed for some design parameter such as clearance between cylinder wall piston, depth of rectangular groove and pressure of sealed hydraulic fluid. In this paper, we analyze displacement and stress of Wearing by finite element analysis to understand Contact Behaviour Characters.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.10
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• pp.1251-1256
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• 2014

The use of lubrication oil is of many purposes and one among them is to drive the engine mounted on a ship. Hence the supply of clean lubrication oil is important. And an oil purifier is one of key components in marine diesel engines. At present, the element type full-flow oil filter has been widely used for cleaning the engine oil. The self-driven centrifugal oil purifier is a device which is used to remove the impurities in lubrication oil using a jet flow. The flow characteristics and the physical behaviors of particles in this self-driven oil purifier were investigated numerically and the filtration efficiencies were evaluated. For calculations, a Computational Fluid Dynamics method is used and the Shear Stress Transport turbulence model has been adopted. The Multi Frames of Reference method is used to consider the rotating effect of the flows. The influence of centrifugal forcehas been numerically investigatedto improve filtration efficiency of tiny particles. As a result of this research, it was found that the particle filtration efficiency using the only center axis rotating and outer wall rotating system are higher than that of the fully rotating system in the self-driven oil purifier.