• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.3
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• pp.1253-1258
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• 2014

The tribological properties of TiC, TiN and TiC/TiN coatings on steels prepared by the cathodic-arc (CA) ion plating technique were investigated. Experiments were carried out on a tribo-test machine using a Falex journal V block system. The friction and wear characteristics of the coatings were determined by varying the applied load and sliding speed. The TiC, TiN and TiC/TiN coatings markedly increased the tribological characteristics of the surface. As far as a single layer coating was concerned, TiN goes better results than TiC. However, the TiC/TiN multilayer coating performed better than either single layer coating. The major factor in the improved performance of the multilayer coating was the role of TiC in improving the adhesion between the external TiN layer and the substrate steel.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.109-116
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• 2001

In this study, the effects of oxide layer formed on the contact parts of TiN coated ball and steel disk in sliding are investigated. Also wear mechanism to form the oxide layer and the characteristics of the oxide layer formation are investigated. AIS152100 steel ball is used for the substrate of coated ball specimens. Two types of coated ball specimens were prepared by depositing TiN coating with 1 and 4um in coating thickness. AISI1045 steel is used for the disk type counter-body. To investigate the effect of oxide layer on the contact parts of the two materials, the tests were performed both in ambient for forming oxide layer on the contact parts and in nitride environment to avoid oxidation. And to study the effects of surface roughness of counter-body, TiN coating thickness and contact load of sliding test on the characteristics of oxide layer formation on counter-body, various tests were carried out. From the results, the friction characteristics between the two materials was predominated by iron oxide layer that formed on wear track on counter-body and this layer caused the high friction. And the formation rate of the oxide layer on wear track increased as the real contact area between the two materials increased as the contact load increased, the TiN coating thickness decreased and the surface of counter-body smoothened.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.4
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• pp.67-73
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• 2014

The dry sliding wear behavior of graphite that is used as the sealing material to cut off hot gas was evaluated as a function of applied load, sliding speed and temperature. The reciprocating wear tests were carried out at room temperature and elevated temperatures. An attempt has been made to develop a mathematical model by response surface methodology and an analysis of variance technique was applied to confirm the validity of the developed model. Also, the wear mechanism was compared through the observation of the worn surface by SEM analysis.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.5
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• pp.113-120
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• 2013

Graphite is commonly used as a solid lubricant leading to low friction coefficient and abrasion. In this study, wear behavior of sealing graphite(HK-6) at elevated temperature was evaluated. Reciprocating wear test was carried out as wear occurred graphite as a seal(HK-6) is positioned between the liner and driving shaft. Variables which are temperature, sliding speed and contact load are set. This study suggest optimized environment conditions through the wear properties of graphite.

• Journal of the Korean Society for Railway
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• v.18 no.5
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• pp.410-418
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• 2015

A slider of the pantograph undergoes uneven and abnormal wear due to sliding contact with the catenary. In the case of rain, the loss of lubricant increases the frictional resistance for the reciprocating motion between the catenary and the slider, accelerating local wear. The slider in the winter should have good wear resistance, which can be achieved through alloy design. Uneven and abnormal wear were not observed in the results of a driving test using a wear resistant slider. It was found that the increased density of the slider enhanced the corrosive effects of Fe-Ti, preventing the occurrence of abnormal wear by maintaining the wear and arc resistance in the rainy season. Also, mechanical and electrical wear did not affect the composition of the slider, and this improved the wear resistance. Inaddition, the slider was applied to an entire train and was tested during driving; ananalysis of the correlation of the catenary was performed, including during the rainy season and the winter season.

• Journal of the Korean Institute of Gas
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• v.12 no.2
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• pp.7-11
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• 2008

This paper presents the experimental results on the oil leakage characteristics of stem seals depending on the driving distance in LPG vehicle. The increased speeds of the camshaft and oil temperatures do not affect to the oil leakage of the seals because of the low level of driving distances less than 40,000 km. But the increased driving distance over 50,000 km to 100,000 km shows a rapid deteriorating the sealing performance, which may increase the oil leakage through the rubbing surfaces between the poppet valves and stem seals. In this result, the stem seal may be exchanged about the driving distance of 50,000 km to 60,000 km with a currently used stem seal in LPG car. Thus, the stem seal for a poppet valve should be resigned for the increased durability and long life.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.5
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• pp.30-36
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• 2018

Automotive fuel efficiency regulations and air pollution control are hot issues of recent years in the automotive industry. To solve these regulation problems, many studies are continuing to improve the transmission efficiency of transmissions. Tapered roller bearings are useful to improve the transmission efficiency in the recent automobile parts. The frictional losses in the tapered roller bearings are mainly composed of the rolling friction and the sliding friction, and are dependent upon the load, the lubrication, the rotation speed of bearings, and etc. In this paper, the operating conditions of the transmission are defined and then the power losses of each bearing are calculated. In addition, improvement options are suggested after identifying the design factors influenced much by the improvement effect of power loss under the operating conditions of each bearing. We compare the power losses of the entire transmission system due to bearing improvements by comparing the friction losses between the original design and the improved design. Lastly, it is shown that the calculated power losses are valid by comparing the test values and the theoretical values for the frictional torque characteristics of the original and improved bearings.

• Tribology and Lubricants
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• v.39 no.6
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• pp.235-243
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• 2023

This paper presents the fabrication process of water-lubricated plastic bearings. Plastic bearings require good mechanical properties and tribological properties as well as elasticity and shock resistance, especially when lubricated in dirty water conditions. In this study, sleeve-type plastic bearings are produced by winding a prepreg sheet, which primary contains nitrile rubber (NBR)-modified epoxy, self-lubricating fillers, and various types of lattice-structured reinforcing fibers such as carbon, Aramid, and polyethylene terephthalate. A thermosetting epoxy is chemically modified with NBR to impart elasticity and low-friction characteristics in water conditions. Experimental investigations are conducted to examine the mechanical and tribological characteristics of the developed bearing materials, and the results are compared with the characteristics of a commercial plastic bearing (Thordon SXL), well known as a water-lubricated bearing. A Thordon bearing (mainly composed of polyurethane) exhibits an extremely low load-bearing capacity and is thus only suitable for medium loading (1~10MPa). The tribological characteristics of the test materials are evaluated through Falex block-on-ring (LFW-1) friction and wear tests. The results indicate that friction exhibited by the carbon-fiber-reinforced NBR-10wt.%-modified epoxy composite material, incorporated with the addition of 20wt.% UHMWPE and 6wt.% paraffin wax, is lower than that of the Thorden bearings, whereas its wear resistance surpass that of Thorden ones. Because of these features, the load carrying capacity of the fabricated composite (>10MPa) is higher than that of the Thorden bearings. These results confirm the applicability of water-lubricated plastic bearing materials developed in this study.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.2
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• pp.276-285
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• 2012

The objective of this research is to develop the coating technique by a porous self-fluxing alloy for improving the mechanical properties of run-out table roller surface with the hot rolling. To enhance the durability of run-out table roller with the hot rolling, the high hardness of roller surface should be maintained at high temperatures, and the improvement of wear resistance, corrosion resistance, heat resistance, burn resistance and adhesion resistance should be maintained. In order to be able to transport reliably a hot rolled steel sheet, also, the appropriate friction coefficient on the roller surface should be maintained and the slip between roller and steel should not occur. In this study, the wear resistance of roller increases after the self-fluxing alloy is changed to a cermet by adding the tungsten carbide(WC), and the coefficient of friction increases and the ability of grip is improved because the porosities are made by coating with fine iron powder on the roller surface. As a result, it is found that the ability of grip between the steel and the roller coated by a porous self-fluxing alloy contained to 5 ~ 10 wt% of Fe in the coating layer is improved compared to the roller coated by Ni-Cr. This is because the porosities are made after Fe contained in the roller is partially alloyed by heating with a furnace in the fusing process and the rest is eliminated by oxidation and dissolution.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.1
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• pp.145-159
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• 2004

A mathematical model and its computer solution program were proposed to analyze the motion of contact lenses which are being subject to lid-blinking. The equation was derived by incorporating an acceleration induced lid's force exerting on the contact lens, the viscous damping resistance in the tear layer beneath the lens and the sliding frictional force between the lid and the contact lens surface into the formulation of differential equation describing the vibration. The model predicts the time-dependent displacement from the equilibrium postion during/after the blinking. During the blinking, as the time for the completion of one cycle of blinking decreases the off-the-equilibrium displacement of contact lens increases while the decrease of diameter in the contact cause the opposite effect. It is found that lid pressure exerting on the lens cause an insignificant lens displacement from the equilibrium position. After blinking the frequency of damped oscillation of contact lens decreases as the diameter of lens increases, due to the incresed surface while the reduced blinking time does not cause a significant frequency change. This is because that driving force for the contact lens movement posterior to blinking is the capillary-induced force not the lid force.