• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.446-454
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• 2011

The noise of the subway has become a social issue and includes very complex reasons. The friction between rail and train wheel is the most important reason of the noise. In this study, we developed MFI(Multi Fluid Injection) System which sprays the mixed fluid(water, anticorrosive and lubricant) on the rail when the train is approaching to reduce the friction. To verify the system's effect, we measured the internal and external noise of the running train. The measured and analyzed results show that MFI system reduce the noise of the running subway.

• 한국정밀공학회지
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• 제14권4호
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• pp.56-63
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• 1997

Sealing of lubricant-air mixture in the high performance machining center is one of most the important characteristics to carry out enhanced lubrication. High speed spindle requires non-contact type of sealing mechanism. Evaluating an optimum seal design to minimize leakage is concerned in the aspect of flow control. Effect of geometry and leakage path are evaluated according to variation of sealing geometry. Velocity, pressure, turbulence intensity of profile is calculated to find more efficient geometry and variables. This offers a methodological way of enhancement seal design for high speed spindle. The working fluid is regarded as two phases that are mixed flow of oil phase and air phase. It is more reasonable to simulate an oil jet or oil mist type high speed spindle lubrication. Turbulence and compressible flow model are used to evaluate a flow characteristic. This paper considers a design effect of sealing capability of non- contact type seals for high speed spindle and analyzes leakage characteristics to minimize a leakage 7 on the same sealing area.

• 동력기계공학회지
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• 제15권6호
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• pp.41-46
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• 2011

Refrigerant oil reduces friction between piston and cylinder of compressor and is normally hard to mix or dissolve in refrigerant. Oil separator deprives refrigerating oil from mixed solution of refrigerant and refrigerant oil. Sometimes much machine oil is carried into an evaporator and is applied to surface of the evaporator, and then disturbs heat transfer through it. Well-made oil separator helps refrigerating system stable and evaporator sustain full capacity. In this paper, new oil separate with different way to structure is suggested and tested. As result the new separates is 13% higher at 0C with 10% mixture and 6% higher at 0C with 20% mixture.

• KSTLE International Journal
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• 제10권1_2호
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• pp.43-47
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• 2009

Influences of carbonaceous ingredient as a solid lubricant in automotive friction materials on friction properties were studied. Three types of carbonaceous ingredients such as natural graphite, artificial graphite, and cokes were mixed using a constrained mixture design. A 1/5 scale brake dynamometer was used to obtain tribological properties. Results showed that cokes substantially increased the friction coefficient, and natural graphite effectively reduced stick-slip phenomena. This significant difference was attributed to the formation of the friction film on the brake pad which was shown to be strongly dependent on the graphite types. The different crystal structures of the carbonaceous solid lubricants played a significant role in the formation of friction film at the interface.

• Tribology and Lubricants
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• 제24권5호
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• pp.264-268
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• 2008

A large number of additives have been used with the efforts of improving the performance of lubricants used along with the development of internal combustion engine. In this study, nano-sized graphite was used as liquid-lubricant additive. In order to disperse graphite into oil, we esterified the nano-carbon manufactured by our company with various types of alcohol. After measuring the anti-wear in accordance with the types of alcohol and added concentration, it has been found that its anti-wear/friction decrease has been improved in case of adding 0.1% of the sample composed with C12/14 mixed alcohol & hexadecanol.

• 한국결정성장학회지
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• 제16권3호
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• pp.121-126
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• 2006

HVOF thermal spray coating of Co-alloy T800 is progressively replacing the classical hard coatings such as chrome plating because of the very toxic $Cr^{6+}$ ion known as carcinogen causing lung cancer. For the study of the possibility of replacing of chrome plating, the wear properties of HVOF Co-alloy T800 coatings are investigated using the reciprocating sliding tester both at room and at an elevated temperature of $1000^{\circ}F\;(538^{\circ}C)$. The possibility as durability improvement coating is studied for the application to the high speed spindles vulnerable to frictional heat and wear. Wear mechanisms at the reciprocating sliding wear test are studied for the application to the systems similar to the sliding test such as high speed spindles. Wear debris and frictional coefficients of T800 coatings both at room and at an elevated temperature of $1000^{\circ}F\;(538^{\circ}C)$ are drastically reduced compared to those of non-coated surface of parent substrate Inconel 718. This study shows that the coating is recommendable for the durability improvement coatings on the surfaces vulnerable to frictional heat. The sliding surfaces are weared by the mixed mechanisms such as oxidative wear, abrasion by the sliding ball slurry erosion by the mixture of solid particles and small drops of the melts and semi-melts of the attrited particles cavitation by the relative motions among the coating, sliding ball, the melts and semi-melts. and corrosive wear. The oxide particles and the melts and semi-melts play roles as solid and liquid lubricant reducing the wear and friction coefficient.

• 한국전산구조공학회논문집
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• 제15권1호
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• pp.155-164
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• 2002

저널과의 마찰과 마멸을 줄이기 위하여 저널베어링이 사용된다. 저널베어링은 유체 윤활 상대에서 사용되나, 압력이 지나치게 높거나 회전 속도가 작아지면 탄성 유체 윤활 상태의 유막이 파괴되어 접촉부의 돌기가 접촉되는 경계 윤활 상태가 된다. 따라서 혼합 윤활 상태가 되면 저널베어링의 마멸량이 증가하게 된다 본 논문은 마멸율을 최소화함으로 저널베어링의 수명을 연장하는 최적설계를 수행하였다 목적 함수로 혼합 윤활 영역에서 적용되는 마멸을 함수를 사용하였고, 저널베어링 설계에서 고려할 성능 인자들인 마찰 손실, 안정 한계 속도, 유막 파라미터 등을 제약 함수로 사용하였다. 저널베어링 형상을 나타내는 베어링 반경, 축 반경, 베어링 폭 등에서 본 연구는 베어링 반경을 설계 변수로 하였다. 정식화한 설계인자를 이용하여 저널베어링의 최적 설계를 순차 이차 계획법인 PLBA알고리즘을 사용하여 수행하였다.

• Tribology and Lubricants
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• 제34권5호
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• pp.191-196
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• 2018

Bunker C is used in heavy-lift ships, furnaces, and boilers for generating heat, and power. Bunker C has only four regulations for quality standards and is rarely inspected in Korea. For these reasons, other oils such as used lubricant oil are commonly blended with Bunker C. This illegal mixture of fuel can damage the boilers, engines and affect the environment adversely. In this study, we investigate the fuel properties and perform atomic analysis of illegal Bunker C blended with used lube oil. The test results show that higher quantities of used lube oil in Bunker C have higher flash points, total acid numbers, copper corruption, solid contamination, and metal components. Further, increasing quantities of used lube oil in Bunker C cause lower viscosity, sulfur, and V content. However, adequate sample (approximately 1 L) is needed to evaluate presence of adulterants in Bunker C, we attempted the SIMDIST analysis. In the SIMDIST chromatogram, the used engine oils are detected for longer retention times than Bunker C owing to the high boiling point. We also quantitatively analyzed the lube oil content using SIMDIST.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2010년도 춘계학술발표대회
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• pp.41.2-41.2
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• 2010

In this work, HAp-(t-ZrO2) ceramic composites of biomimic artificial bone were fabricated by multi-extrusion process in order to replace nature bone. HAp-(t-ZrO2) and graphite powders were mixed separately with ethylene vinyl acetate (EVA) and stearic acid using shear mixer. Extruded HAp-(t-ZrO2) filaments and carbon filaments were arranged in the die to fabricate the first pass filament. The first pass filaments were arranged in the same die with a central carbon core for making the space for spongy bone. Burning out and sintering processes were performed to remove the binder and lubricant. The microstructure channel diameter was researched around $300{\mu}m$. Microstructure analysis was carried out by OM, SEM, and $\mu$-CT. Compressive strength was investigated for the artificial bone. Some preliminary bio-compatibility test was evaluated.

• Tribology and Lubricants
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• 제11권5호
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• pp.136-143
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• 1995

The effect of additive chemistry on the serface fatigue of gears was investigated using the FZG gear tester and fluids based on an API GL-5 grade oil. Surface fatigue lives were determined as a function of load and additive chemistry. At 1.52 GPa, the removal of the primary extreme pressure additive (EP) from the fully formulated gear oil decreased the fatigue life of gears slightly (4%), however, the removal of the primary antiwear additive (AW) decreased the fatigue life of gears significantly (83%). At 1.86 GPa, the removal of the EP additive from the fully formulated gear oil decresed the gear fatigue life 27%, however, the removal of the primary AW additive decreased the fatigue life of gears significantly (75%). Micropitting was the dominant surface morphology in the dedendum of gears tested With two oils at load stage: one using the complete additive package, and a second where the EP additive has been removed. However, spalling is the primary failure mode of gears tested without an AW additive independent of whether an EP agent was present. Surface analysis of pinion gears showed the formation of a mixed phosphate/phosphite-oxide layer on the surface of gears tested with fluids containing an AW. Formation of this layer seems to be key to long fatigue life.