• Tribology and Lubricants
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• v.5 no.1
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• pp.57-63
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• 1989

The soluble Mo-DTP compounds as lubricant additives for reducing friction and wear, increasing loadcarrying capacity, and as antioxidants is very important as a new additive developed in these day. The method of the compounds are described and the composition is analyzed with $^{31}$P NMR spectrometer. The wear test is conducted with 4-ball machine and the debris are analyzed by ferrography. Also the tribological performance of Mo-DTP compounds are compared with Moly Van L and Zn-DTP.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.4
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• pp.6-11
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• 2002

Formability in deep drawing process depends not only on a drawability of workpiece material but also on process conditions such as die punch comer radius, lubricant conditions, punch-die clearance etc. For instance, bending resistance should be reduced by increasing die round appropriately, drawing load should be minimized by improving the lubricant condition between die and material, and blanking load should be increased by selecting a pertinent punch round and by augmenting the friction resistance in punch. In this study, a multi-stage deep drawing process is analyzed using ABAQUS. The effects of formability factors, such as die shoulder radius, punch-die clearance and friction coefficient are investigated, and the results are also discussed in detail.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.269-274
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• 2004

It is important to decide the minimum film thickness and viscosity variations of a multigrade lubricant in the contact surface under the high pressure conditions. By carrying out acceleration, deceleration, and various sliding-rolling ratio movement between two contact bodies, it is experimented that film formation variations in the contact surface are captured with multigrade lubricants in order to exactly investigate the variations of film formations. Optical interference images are continuously captured with high resolution CCD camera during the captured period of acceleration, deceleration. The friction forces between the contacting bodies are also measured simultaneously with the film formation.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.158-163
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• 2003

Several simulation techniques have been developed which are not practical deformation processes but are designed to embody specific tribological aspects. Sliding rolling type friction test machine (Cold rolling tribosimulator) was developed to simulate the tribological phenomena at the roll bite in real mill by laboratory scale. A rolled material is fed at a low speed of Max. 1/20 to that of roll speed, so as to obtain simultaneous plastic deformation in the material during rotation of the rolls in simulator. New cold rolling tribe-simulator is effective for evaluation of the lubricity of lubricant in cold rolling process.

• Journal of the korean Society of Automotive Engineers
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• v.12 no.4
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• pp.56-65
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• 1990

Wet-friction materials have been widely used for clutches and brakes of automotives over past several decades. In order to enhance its performance, its friction behaviour should be fully understood. It is, however, still not at hand and therefore an attempt was made to have some more understanding of friction behaviour of wet-friction materials. Measurements of coefficient of friction were made with the variation of lubricants, lub. temperature, sliding velocity, and contact pressure. In addition, the effects of both the viscosity of lubricants and the porosity of materials on the coefficient of friction were also investigated. It can be concluded that the coefficient of friction is decreased as the concentrations of the resin and inorganic fillers are increased, and it tends to decrease with the increase in the lubricant temperature and sliding velocity.

• Tribology and Lubricants
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• v.19 no.3
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• pp.159-166
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• 2003

This research for replacement of chlorine or sulfur based EP(extreme pressure) -additives which is restricted materials by environmental regulation. The subject of this study is as follows, 4-ball test and friction coefficient test were experimented in accordance with temperature and velocity, compounding with several organic or inorganic metallic elements. After 4-ball test, wear area of steel ball was analysed by SEM-EDX. As the analysis, organic and inorganic elements make a effect for extreme pressure lubricity. It is shown that the friction coefficient of lubricant which includes chlorine or sulfur additives, the scoring phenomenon is found accord-ing to temperature and the scuffing phenomenon at 200$^{\circ}C$. Applying to Na, P, S, Zn, Ca based on inorganic and organic elements, the result showed that friction coefficient is decreased more and more, as increasing temperature of lubricant. The additive based on S, Cl, P elements is effect far extreme pressure in the sample#1 and Na, P, S, Zn, Ca in sample #2. These elements are environmental contaminants and S, Cl based on EP additives which are very popular in domestic industry, when they are properly composed with non-chlorine based on additives and Na, P, S, Zn, Ca organic or inorganic elements. It is showed that lubricity and excellent anti-wear properties.

• Tribology and Lubricants
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• v.36 no.2
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• pp.55-63
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• 2020

Recently, graphene has attracted considerable attention owing to its unique electrical, optical, thermal, and mechanical properties. The broad spectrum of applications from optics, sensors, and electronics to biodevice have been proposed based on these properties. In particular, graphene has been proposed as a protective coating layer and solid lubricant for microdevices and nanodevices because of its high mechanical strength, chemical inertness, and low friction characteristics. During the past decade, extensive efforts have been made to explore the tribological characteristics of graphene under various conditions and to expand its applicability. In addition to the experimental approaches, the molecular simulations performed provide fundamental insights into the friction and wear characteristics of graphene resulting from molecular interactions. This work is a review of the studies conducted over the past decade on the tribological characteristics of graphene using molecular simulation. These studies demonstrate the principal mechanisms of the superlubricity of graphene and help clarify the influences of surface conditions on tribological behavior. In particular, the investigation of the effects of the number of layers, strength of adhesion to the substrate, surface roughness, and commensurability provides deeper insights into the tribological characteristics of graphene. These fundamental understandings can help elucidate the feasibility of graphene as a protective coating layer and solid lubricant for microdevices and nanodevices.

• Journal of Mechanical Science and Technology
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• v.17 no.9
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• pp.1276-1286
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• 2003

The performance of porous bearing under different lubricants and lubricating conditions was experimentally investigated in this study. In order to carry out the experiments, a new test rig was designed to determine the tribological properties of based sintered bronze journal bearings that were manufactured by powder metallurgy (P/M) techniques. To determine the effects of lubricating conditions with and without oil supplement (OS) on the tribological characteristics of these bearings under static loading and periodic loadings, some experiments were carried out using different lubricants. In the tests, pure base oil (SAE 20W50), two fully formulated commercial engine oils (SAE20W50) and lubricating oils with commercial additive concentration ratio of 3％ were used. The worn surfaces of test bearings were examined using optical microscopy. Experimental results showed that the change in friction coefficient was more stable and in smaller magnitude under static loading than that of periodic loading. In addition, the friction coefficient and the wear rate conducted with base oil resulted in higher values than those of fully formulated oils with and without OS lubricating conditions. The experimental results obtained in this study indicated that the correct selection of lubricant and suitable running conditions were very important on the tribological characteristics of porous bearings.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.78-87
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• 2001

The friction and wear behaviors of WC/C multilayer coating were investigated by using a pin on disk type tester. The experiment was conducted by using silicon nitride (S $i_{3}$ $N_{4}$) as a pin material and WC/C multilayer coating on bearing steel (STB2) as a disk material, under various environments that are atmospheric conditions of high vacuum( 1,3$\times$10$^{-4}$ Pa), medium vacuum( 1.3$\times$10$^{-l}$Pa). ambient air( 10$^{5}$ pa)(3 types) and relative humidity(2~98%) conditions. The results showed that WC/C coating fracture was suddenly increased with increasing degree of vacuum, because of high adhesion. So, WC/C coating could not be displayed their ability as solid lubricant. WC/C coating could be displayed better abilitv as solid lubricant with increasing relative humidity. because of oxide film, size and shape of wear debris. The friction coefficient and specific wear rate became better about RH 50%.%.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.16-21
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• 2002

Generally, Oxidization film are generated by friction and wear in lubricant oil. It is effect that the heat and pressure act on contact area. Because the electrons movement progress the oxidization, if the electrons movement be regulated, the thickness of oxidization film can be regulated and friction characteristics can be improved. But electronic current can deteriorate friction characteristics, so various characteristics must be investigated on transforming of electronic current. Therefor, using the Norton equation, short current were transformed between ball and disk. Also, an experiment was carried out using ball on disk type tester. So, we studied up on effect of current for friction characteristics.