• Journal of the Korean Society for Heat Treatment
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• v.8 no.3
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• pp.182-186
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• 1995

SCM440, which is widely used as the diesel engine piston of vessel, has been hardened by a $CO_2$ laser with the wavelength of $10.6{\mu}m$. Laser hardening experiment has been carried out for the condition of a laser power 1kW, the travel speed between 0.4 and 1.5m/min, and a rectangular-Gaussian beam. Residual stress has been measured by using middle point technique of half value width of X-ray diffraction method. It was found that the compressive residual stress with the range between 400 and 600MHz has distributed in the laser hardening zones and the tensile residual stress between 100 and 200MHz has distributed in the boundary of hardening zones.

• 한국연소학회:학술대회논문집
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• 2002.06a
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• pp.33-38
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• 2002

An optical single cylinder diesel engine equipped with a common-rail injection system has been built to investigate diesel combustion and emission characteristics. Three optical widows (piston crown quartz for bottom view of the cylinder, upper piston quartz for allowing laser sheet and liner quartz for side view) have been placed in the optical engine to visualize spray characteristics and combustion process inside the cylinder. Before doing further research using various optical diagnostics with the optical engine, fundamental combustion experiments and flame visualization incorporating a high speed motion analyser have been carried out with a wide range of engine operating conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.3
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• pp.1-8
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• 2001

The flow field inside a cylinder of four-valve Sl engine was investigated quantitatively using a three-dimensional Laser Doppler Velocimetry system, to determine how stroke changes affect the flow field. The purpose of this work was to develop quantitative methods which correlate in-cylinder flows to engine performance. For this study, the sane intake manifold, engine head, cylinder, and the piston were used to examine the flow characteristics in different strokes. Quantification of the flow field was done by calculating three major parameters which are believed to adequately characterize in cylinder motion. These quantities were TKE, tumble and swirl ratios. The LDV results reveal that flow patterns are similar, the flow velocities scale with piston speed but another parameters such as TKE, and tumble and swirl numbers are not the same for different stroke systems.

• Transactions of Materials Processing
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• v.10 no.3
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• pp.223-234
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• 2001

The characteristics of thixoforming process can decrease liquid segregation because of the improvement in fluidity in a globular microstructure state and utilizes flow without an air entrapment. Therefore, in order to obtain the sound parts of metal matrix composites by using thixoforming process which has co-existing solidus-liquidus phase, it is very important to design a die shape property and to obtain the fabrication conditions which affect the unifomity of the solid fraction on unfilling state and various defects throughout the fabricated parts. The die designs and fabrication conditions to obtain the good piston part are proposed for thixoforging process of metal matrix composites. When reheated metal matrix composites billets were transferred to the closed die gate, thixoforging were carried out under the various pressure(60, 80, 100MPa) with controled forging speed. The mechanical properties such as hardness and tensile strength for thixoforged parts have been investigated after T6 heat treatment.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1215-1220
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• 2008

The aim of this paper is to perform a finite element analysis that will have the ability to predict the seal performance characteristics, such as deformation, contact load and friction and also is to provide a means of potential seal designs, which can reduce the time and cost of designing the performance of the seal. The material property tests of elastomer seal are performed to obtain the hyperelastic properties and The Mooney-Rivlin constants are determined from these test results. A 2D modelling of the seal cross section is performed to simulate the contact behavior between the seal on the piston and the cylinder bore under operation conditions. The deformation behavior, contact load and friction of an elastomer seal is analyzed by a finite element method which performs three analytic phases of interference fit, the variations of pneumatic pressure and piston movement under the operational conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.111-119
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• 1997

The operating characteristics of the check valve in the clutch piston of an automatic transmission have a great effect on the shifting performance. This paper addresses the modeling, dynamic analysis, and optimization of the check valve. It was found that the vortex causes a pressure drop, which is related to the rotating speed of the clutch piston, oil volume discharged from the check valve, and valve geometry. Maximizing the oil volume discharged, geometry of the check valve is optimized. The results can be used to design an improved check valve which provides a suitable oil pressure curves for achieving smoother shifting.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.2
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• pp.129-136
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• 2010

Axial piston pumps have been widely used as power sources for hydraulic systems, but studies on the fluid flow within the pump have been usually performed using 1-D analysis because of the difficulties in considering the fluid compressibility, high-speed revolution, variation of the flow rate, and complicated geometry. The goal of this study was to understand the hydraulic fluid flow within axial piston pumps by using the 3-D numerical method and the process of generating discharge pressure ripples. To improve the convergence and robustness of the simulation model, a grid system was constructed with hexahedron-type grids around the valve plate. Furthermore, we employed an empirical formula to describe the relationship between the oil density and pressure. The CFD (computational fluid dynamics) results compared well with the experimental data.

• International Journal of Automotive Technology
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• v.7 no.5
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• pp.585-593
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• 2006

The effect of the shape of the side wall on vaporization and fuel mixture were investigated for the impinging spray of a direct injection(DI) gasoline engine under a variety of conditions using the LIEF technique. The characteristics of the impinging spray were investigated under various configurations of piston cavities. To simulate the effect of piston cavity configurations and injection timing in an actual DI gasoline engine, the parameters were horizontal distance from the spray axis to side wall and vertical distance from nozzle tip to impingement plate. Prior to investigating the side wall effect, experiments on free and impinging sprays for flat plates were conducted and these results were compared with those of the side wall impinging spray. For each condition, the impingement plate was located at three different vertical distances(Z=46.7, 58.4, and 70 mm) below the injector tip and the rectangular side wall was installed at three different radial distances(R=15, 20, and 25 mm) from the spray axis. Radial propagation velocity from spray axis along impinging plate became higher with increasing ambient temperature. When the ambient pressure was increased, propagation speed reduced. High ambient pressures tended to prevent the impinging spray from the propagating radially and kept the fuel concentration higher near the spray axis. Regardless of ambient pressure and temperature fully developed vortices were generated near the side wall with nearly identical distributions, however there were discrepancies in the early development process. A relationship between the impingement distance(Z) and the distance from the side wall to the spray axis(R) was demonstrated in this study when R=20 and 25 mm and Z=46.7 and 58.4 mm. Fuel recirculation was achieved by adequate side wall distance. Fuel mixture stratification, an adequate piston cavity with a shorter impingement distance from the injector tip to the piston head should be required in the central direct injection system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2424-2429
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• 2015

In an oil hydraulic piston pump, the cylinder block and valve plate in high speed relative sliding motion have the characteristics which should be extremely controlled for the optimization of leakage and friction losses, and pressure-resistance design of them is very important for high pressure performance. But the studies on the stress analysis of those parts have not been performed briskly. Therefore, in this paper, the stress and displacement distributions of the cylinder block and valve plate in the oil hydraulic piston pump with a swash plate type are discussed through the static stress analysis using CATIA V5. The stress and displacement of the cylinder block are more influenced by the axial pressure than by the radial pressure, and are larger by approximately 66% and 30%, respectively. The results show that a review of the material and shape of the valve plate is required.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.6
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• pp.24-30
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• 2013

This paper studies the comparative analysis on two different internal cushion devices (the types of needle and relief valve) used to absorb the energy which is generated when the pneumatic cylinder moves with the load at meter-out speed control system. The effect at varying the piston velocity under same driving condition is mainly investigated. The simulation results on pressure in the cushion chamber and the dynamic behavior of the relief valve type cushion device are compared with the needle valve type. Design and performance are improved with the cushion configuration of better quality at high-speed pneumatic cylinder. Based on the relation between absorbed energy and impact energy at cushion process, cushion performance at pneumatic cylinder is evaluated.