• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.06a
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• pp.42-47
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• 2000

The friction and lubrication characteristics of joint cartilage were investigated using the metatarso-phalangeal joint cartilage of rabbit against rotating stainless steel disk. Friction tests were conducted by dry and bovine serum lubricated sliding at room and body temperatures. For the dry sliding tests, low friction coefficient of 0.1-0.15 was observed at the early period of test, and then the friction coefficient increased as a test continued. With increasing applied load the early period of low friction lengthens. For the lubricated sliding tests, the coefficient of friction decreased as the applied load increased. And also the coefficient of friction decreased continuously to 0.07 as the test duration increases. These results can be interpreted that the squeeze or weeping lubrication mechanism dominates the friction and lubrication characteristics in the joint cartilage of rabbit.

• Journal of Industrial Technology
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• v.28 no.A
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• pp.195-198
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• 2008

Graphite and $MoS_2$ were added respectively to the Cu/Sn bond materials of the same composition as a lubricant in order to find out the effect of lubricants on the mechanical properties and the increase in density of the sintered products for microblades. The addition of $MoS_2$ as a lubricant was more beneficial to strength, fracture toughness, and hardness as well as densification than graphite. $MoS_2$ seemed to be more effective in reducing the friction between the metallic powders and die wall during hot pressing process. Due to the better wettability of MoS2 with bond metal alloy, less amount of interfacial defects which is detrimental to mechanical properties use observed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.244-247
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• 2001

Lubricanting characteristics in the warm forging have influence on forgeability of products. but Research on deformation characteristic of warm forging on the lubricant and lubricating method lack. This paper deform a bevel gear by warm forging and evaluate deformation loads and quality of products by each lubricants and lubricating method using oil-based lubricants(Soy, Oildag) and water-based lubricants(Deltaforge $\#31$, Renite S-26-X, Deltaglaze $\#151$). In conclusion, the less a deformation load by lubricants the more improvement a quality of product in manufacture of a bevel gear and water-based lubricants in the warm forging reduce a deformation load and improve a quality of products. Especially, Deltaforge $\31$ have excellent characteristic in the warm forging.

• Tribology and Lubricants
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• v.25 no.5
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• pp.335-341
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• 2009

Elastohydrodynamic lubrication (EHL) analysis shows that film thickness is very flat in the contact area and pressure distribution is somehow similar to that of Hertzian contact pressure except the outlet region with pressure spike. These typical patterns of EHL film thickness and pressure are the cases under the steady contact conditions of applied loads and speeds. However, many engineering contacts are rather under the conditions of varying loads and contact speeds, and therefore the predictions for endurance life and performance of machine elements with steady EHL analysis are not suitable in many occasions. This study shows the differences in film thickness formation and pressure distribution between steady and transient contact conditions in several contact cases.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1993.04a
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• pp.70-79
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• 1993

세라믹은 금속에 비해서 밀도가 낮고, 내마멸성이 우수하고, 열팽창계수가 작고, 높은 온도범위에 걸쳐서 안정성과 경도를 유지함으로 기계구조용재료로서 유망시 되고 있다. 앞으로 세라믹부품에 대한 수요는 더욱 증가하리라고 예상하고 있으며, 세라믹의 응용이 시도되고 있는 부품은 더욱 다양화되어가고 있는 추세이다. 그러나, 세라믹재료에 관한 신뢰할만한 데이터베이스는 확립되지 못한 상태이고, 트라이보시스템에 관한 수명예측과 설계를 위한 기초 자료도 확립하지 못한 상태에 있다. 세라믹재료에 관한 수명예측과 설계를 위해서는 세라믹재료의 트라이보시스템(tribosystem)에서의 마멸기구의 규명과 마멸율을 평가할 수 있는 마멸식을 구하는 것이 가장 기본적인 과제라 할 수 잇다. 따라서 본 연구에서는 최신 기법에 의해서 제조된 HIP제 질화규소와 지르코니아를 실험재료로 하여 무윤활하에서의 미끄럼 마찰$\cdot$마멸실험을 수행하여 마찰$\cdot$마멸특성을 규명하고, SEM을 이용한 마멸면의 미시적 관찰을 통해서 세라믹의 마멸기구를 조사하여 세라믹마멸기구의 마멸모델을 제히하고자 한다. 제시된 마멸모델에 파괴역학을 도입하여 이론해석과 고찰을 수행하여 보다 실용적인 세라믹의 마멸율을 평가할 수 있는 새료운 무차원파라메타를 제안하고자 한다.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.105-110
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• 2002

The use of microporous polymer lubricants (MPLs) can eliminate the storage, sealing, and pumping problems associated with liquid lubricants, This paper discusses the use of MPLs for a component as rolling-element bearings. An MPL composed of 40% HDPE and 60% ester oil was synthesized and the MPL was applied to a ball bearing. The MPL ball bearing, filled with the MPL instead of the usual grease pack, tested and compared with the usual grease sealed ball bearing. The MPL applied to a ball bearing showed lubricant properties as good as usual grease, and showed higher performance in bearing oil leakage test, rotating torque test and thermal test at high speed running than usual grease.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.185-192
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• 2002

This paper focused on the dynamic behavior of camshaft in a direct acting type valve train system. To investigate camshaft behavior, transient vibration analysis is performed by using the transfer matrix method. The camshaft is treated as lumped mass system supported by spring and damper. Front the presented analytical model, we could predict dynamic behavior of camshaft, shaft locus within bearing and bearing load. The presented mode and results will be very helpful to design the optimal camshaft and valve train system.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.156-161
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• 2002

Results of theoretical investigations on acoustical properties of hydrodynamic proceeding bearings are presented. Nonlinear analysis of rotor bearing system including rotor imbalance is performed in order to obtain acoustical properties of hydrodynamic proceeding bearings. Furthermore, a cavitation algorithm, implementing the Jakobsson-Floberg-Olsson boundary condition, is adopted to predict cavitation regions in a fluid film. Acoustical properties of hydrodynamic proceeding bearings are identified through frequency analysis of pressure fluctuation calculated from the nonlinear transient analysis. The results show that the acoustical frequency spectra of hydrodynamic proceeding bearings are pure tone spectra, containing the frequency of the shaft rotation and its super-harmonics. The analysis also shows that the super-harmonics are predominant at neighborhood of the fluid film reformation and rupture regions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.6 s.177
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• pp.1520-1528
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• 2000

This study presents a method for determining bearing stiffness and damping coefficients of air-lubricated slider bearing, and shows influences of air-bearing surface geometry(recess depth, crown an d pivot location) on flying attitude and dynamic characteristics. To derive the dynamic lubrication equation, the perturbation method is applied to the generalized lubrication equation which based on linearized Boltzmann equation. The generalized lubrication equation and the dynamic lubrication equation are converted to a control volume formulation, and then, the static and dynamic pressure distributions are calculated by finite difference method. The recess depth and crown of the slider show significantly influence on flying attitude and dynamic characteristics comparing with those of pivot location.

• Tribology and Lubricants
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• v.21 no.6
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• pp.263-267
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• 2005

The tribological performance of multi-walled carbon nanotubes (MWNT) in mineral oils is investigated at ambient temperature. The frictional forces, wear amounts and cycles to scuffing of the oils with nanotubes and without those were measured using the ball-on-disk tester. It was found that there were little differences in the frictional forces and wear amounts of two oils. However, the scuffing times of oils with nanotubes were much longer than those of oils without nanotubes in sliding tests. The nanotubes were very effective on maintaining the oil gap and protecting the surfaces in boundary lubricated sliding.