• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.3
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• pp.46-54
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• 1993

In order to develop a fuel-efficient gasoline engine oil, an experimental study was conducted using an engine dynamometer, a passenger car and the SRV machine. Oil samples with different viscosity were prepared by adding several friction modifiers to select the best one and also to investigate the effect of the viscosity grade. From the study, we have developed engine oils which result in good fuel economy. The viscosity grade of 7.5W/30 was best among the oils investigated with respect to fuel economy and a fatty amine type friction modifier had the good fuel-economy property.

• KSTLE International Journal
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• v.9 no.1_2
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• pp.10-12
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• 2008

Silicon micro-patterns were fabricated on Si (100) wafers using photolithography and DRIE (Deep Reactive Ion Etching) fabrication techniques. The patterned shapes included micro-pillars and micro-channels. After the fabrication of the patterns, the patterned surfaces were chemically modified by coating Z-DOL (perfluoropolyether, PFPE) thin films. The surfaces were then evaluated for their micro-friction behavior in comparison with those of bare Si (100) flat, Z-DOL coated Si (100) flat and uncoated Si patterns. Experimental results showed that the chemically treated (Z-DOL coated) patterned surfaces exhibited the lowest values of coefficient of friction when compared to the rest of the test materials. The results indicate that a combination of both the topographical and chemical modification is very effective in reducing the friction property. Combined surface treatments such as these could be useful for tribological applications in miniaturized devices such as Micro/Nano-Electro-Mechanical-Systems (MEMS/NEMS).

• Tribology and Lubricants
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• v.12 no.2
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• pp.32-40
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• 1996

The tribological role of copper alloy fine particles in an additive is not well known compared to solid lubricants such as $MoS_{2}$ and PTFE. In this experimental investigation, a series of friction and wear test was undertaken to gain a better understanding of an additive containing copper alloy fine particles and to identify the effectiveness of copper alloy particles in improving tribological performance of the lubricant. Friction and wear of specimens under lubricated contact condition were studied and the worn surfaces were characterized by AES (Auger Electron Spectroscopy), SEM (Scanning Electron Microscopy) and optical microscopy. It was revealed that a copper-contained layer was formed and this layer resulted in considerable reduction in both friction and wear due to its lubricity and anti-wear property. The analysis of worn surface revealed that copper of the fine alloy particles in the additive helps healing the worn surface by plating and filling wear pits.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.3083-3093
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• 1993

Friction and wear at ceramic coated surfaces of aluminum alloy were experimentally studied using a Ring-on-Block wear test machine. Ceramic materials coated on aluminum alloy surfaces were WC, CrC, $Al_{2}O_{3}$ by a plasma spray; and $Al_{2}O_{3}$,$Al_{2}SiO_{5}$, $Na_{2}B_{4}O_{7}$,$Na_{4}P_{2}O_{7}$, and $Al_{2}O_{3}-ZrO_{2}$ composite coating by an Anodic Spark Depositon. They were tested under the sliding wet contact and compared with aluminum alloys and steels. Test results showed that ceramic coated surfaces, in general, have better anti-wear property than those of aluminum alloys due to increase in the surface hardness ; however, they also showed higher coefficients of friction and changes in wear mechanisms, resulting in brittle fractures.

• Journal of the Korean Society of Safety
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• v.18 no.2
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• pp.1-5
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• 2003

By using an approach developed to determine the torque-tension relationship for bolted joints, frictional properties of several typical bolted joints were studied experimentally. The specific property by bolted joints certify that the most significant influence of materials and bearing surface condition. Experiments on thread friction shows that prevailing torque nuts with distorted threads provide benefit for preventing self-loosening of the nut. Repeated tightening-loosening generally increases frictions in a bolted joint. It was noted that the data scatter of the experimental results of frictions in a belted joint may overshadow the influence of size. speed, and contact positions. The results from the experimental investigation will help to better design bolted joints.

• Journal of Power System Engineering
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• v.18 no.6
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• pp.174-179
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• 2014

The wear behavior of epoxy matrix composites filled with nano sized silica particles is discussed in this paper. Especially, the variation of the coefficient of friction and the specific wear rate under the various applied load and sliding velocity were investigated for these materials. Wear tests of pin-on-disc mode were carried out and followed by scanning electron microscope observations. The presence of silica filler in epoxy composites was demonstrated significant influence on the friction and wear behavior of epoxy nanocomposites. With the incorporation of silica filler into the epoxy matrix, reduction of the coefficient of friction and specific wear rate were identified. Wear mechanism was discussed by analyzing the worn surface by scanning electron microscope as well.

• KSTLE International Journal
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• v.8 no.2
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• pp.26-28
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• 2007

Si(100) surfaces were topographically modified i.e. the surfaces were patterned at micro-scale using photolithography and DRIE (Deep Reactive Ion Etching) fabrication techniques. The patterned shapes included micro-pillars and microchannels. After the fabrication of the patterns, the patterned surfaces were chemically modified by coating a thin DLC film. The surfaces were then evaluated for their friction behavior at micro-scale in comparison with those of bare Si(100) flat, DLC coated Si(100) flat and uncoated patterned surfaces. Experimental results showed that the chemically treated (DLC coated) patterned surfaces exhibited the lowest values of coefficient of friction when compared to the rest of the surfaces. This indicates that a combination of both the topographical and chemical modification is very effective in reducing the friction property. Combined surface treatments such as these could be useful for tribological applications in miniaturized devices such as Micro-Electro-Mechanical-Systems (MEMS).

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.465-472
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• 2003

The main concept of base isolation system is to reduce the member forces by decreasing the earthquake forces transmitted to superstructure instead of the conventional techniques of strengthening the structural members. There are two important advantages in friction pendulum systems. The functions of carrying the vertical load and of providing horizontal stiffness are effectively separated. This results in a more stable system that eliminates the need of a fail-safe mechanism. Friction pendulum systems are less sensitive to variations in the frequency content of ground excitation and tend to limit the intensity of the farce imparted to the superstructure. This study investigates the friction coefficients on the FPS test specimens according to the velocity, bearing pressure and test waveform.

• Tribology and Lubricants
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• v.17 no.5
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• pp.386-390
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• 2001

Monolayers such as self-assembled monolayer (SAM) have received considerable attention to reduce stiction and friction in micro-devices and microelectromechanical systems (MEMS). Various organic molecular films were investigated to obtain better understanding of their tribological behaviors and adhesion property. The organic molecular films studied in this work are: epoxysilane SAMs, octadecyltricholosilane (OST), multi-layers composed of epoxysilane SAMs, poly[styrene-b-(ethylene-co-butylene)-b-styrene](SEBS) and compound of epoxy resin and poly (paraphenylene)(EP/PPP). The pull-off forces of these films were also obtained from force-distance curves measured in static mode of operation of atomic force microscope(AFM). Tribological tests were conducted with a ball-on-flat reciprocating friction tester. The OST showed the lowest pull-off force, indicating its low adhesion property. It was revealed that, the OST, EP/PPP and the multi-layer of epoxysilane SAMs, SEBS and EP/PPP exhibited good tribological properties at the lower load (0.3 N) whereas the OST showed best performance at the higher load (1.8 N).

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.326-330
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• 2005

Aircraft composite structure with honeycomb core experiences core crush problem in manufacturing. To prevent core crush additional processes are needed such as core stabilization and prepreg material tie-down and this is the cause of increasing cost. Recent study shows that high friction prepreg prevent core crush without additional process. This paper presents the analysis of high frictional material which attracts lots of interests through physical property, mechanical property and microscopic