• 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 Automotive Engineers
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• v.8 no.5
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• pp.114-120
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• 2000

Friction forces of piston rings for a typical SI engine were independently measured while excluding the effects of cylinder pressure, oil starvation and piston secondary motion using a floating liner system. Friction patterns, represented by 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(mid-stroke and dead centers). The modes were identified on the Stribeck diagram of the dimensionless bearing parameter and friction coefficients which were evaluated at the mid-stroke and at the dead centers. And the frictional modes were estimated to the full operation range. The compression rings behave in the mode where hydrodynamic lubrication is dominant at the mid-stroke and mixed lubrication is dominant at the dead centers under steady operating conditions. However, the oil control ring behave in the mode where mixed lubrication is dominant throughout the entire stroke.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.3
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• pp.1-12
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• 1994

A model engine having a flat cylinder head and a piston face and an off-center intake valve is investigated in this analysis. Calculation domain is confined to the half of the cylinder with swirl free inlet velocity condition. Due to the absence of measured inlet conditions, the inlet flowrates during induction period are calculated from overall mass and energy conservation requirements. Finite difference equation for velocity and pressure were solved by modified SIMPLER algorithm, standard k-$\varepsilon$turbulence model and hybrid scheme. From the result of prediction, dimensionless velocity distribution and turbulence intensities are investigated at each crank angle.

• Elastomers and Composites
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• v.30 no.3
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• pp.235-246
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• 1995

When an O-ring is installed in a high fluid pressure device, a section of the O-ring is extruded into the piston-cylinder clearance gap. Any tendency towards extrusion will induce wear in dynamic applications, leading to premature failure of the seal. In this study, the mechanism of initial extrusion of the O-ring was studied, 1.e., how much amount of the O-ring will be extruded into the clearance gap at a certain pressure. The relationship between extrusion depth and a clearance gap or fluid pressure were studied by finite element analysis (FEA). After that, Salita's experimental data were analyzed. The result is that Initial extrusion depth for an O-ring into a clearance gap was 1.11 times the product of dimensionless pressure difference $(p-p_1)/E$ and clearance gap c. The required pressure $p_1$ for zero extrusion depth was found to decrease logarithmically with increasing clearance gap.

• Wind and Structures
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• v.29 no.6
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• pp.457-469
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• 2019

In this paper, a numerical solution is presented for supersonic flutter analysis of cantilever non-symmetric functionally graded (FG) sandwich plates. The plate is considered to be composed of two different functionally graded face sheets and an isotropic homogeneous core made of ceramic. Based on the first order shear deformation theory (FSDT) and linear piston theory, the set of governing equations and boundary conditions are derived. Dimensionless form of the governing equations and boundary conditions are derived and solved numerically using generalized differential quadrature method (GDQM) and critical velocity and flutter frequencies are calculated. For various values of the yaw angle, effect of different parameters like aspect ratio, thickness of the plate, power law indices and thickness of the core on the flutter boundaries are investigated. Numerical examples show that wings and tail fins with larger length and shorter width are more stable in supersonic flights. It is concluded for FG sandwich plates made of Al-Al₂O₃ that increase in volume fraction of ceramic (Al₂O₃) increases aeroelastic stability of the plate. Presented study confirms that improvement of aeroelastic behavior and weight of wings and tail fins of aircrafts are not consistent items. It is shown that value of the critical yaw angle depends on aspect ratio of the plate and other parameters including thickness and variation of properties have no considerable effect on it. Results of this paper can be used in design and analysis of wing and tail fin of supersonic airplanes.