• KSTLE International Journal
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• 제1권2호
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• pp.91-94
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• 2000

The friction and wear behavior of MoS$_2$coatings was investigated using a pin and disk type tester. The experiment was conducted with silicon nitride as the pin material and MoS$_2$-on-bearing steel as the disk material under different operating conditions that included linear sliding velocities within a range of 2266 mm/sec, normal loads varying from 9.829.4 N, corresponding to maximum contact pressures of 1.782.83 Gpa, and high vacuum, medium vacuum, and ambient air atmospheric conditions. The results showed a low friction coefficient far the coating in a high vacuum, plus the friction coefficient and wear volume increased with an increased normal load. Furthermore, under high load conditions, the friction coefficient and wear volume also increased with an increased sliding velocity.

• Tribology and Lubricants
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• 제12권3호
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• pp.48-54
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• 1996

Examined in this paper, is the effect of B$_{4}$C addition on the frictional characteristics of Cu-Sn based sintered friction materials. For the specimens 1wt%, 2wt% and 4wt% of B$_{4}$C were added into the reference material. A pin-on-disk type friction tester was used to,measure the friction torque with respect to the surface temperature and sliding distance. Wear mechanism of each specimen is analyzed in the view point of the oxide film formation. The specimen containing 4wt% of B$_{4}$C showed stable friction and low wear since the oxide film was sustained up to higher surface temperature ranges.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제30회 추계학술대회
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• pp.94-100
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• 1999

The friction and wear behavior of MoS$_2$Coatings were investigated using a pin and disk type tester. The experiment was conducted using silicon nitride as pin material and MoS$_2$-on-bearing steel as disk material under different operating conditions that include linear sliding speeds in the range of 22~66mm/sec, normal loads varying from 9.8~29.4N, corresponding to maximum contact pressure of 1.78~2.830GPa and atmospheric conditions of high vacuum, medium vacuum, ambient air. The results showed that low friction coefficient of the coating has been identified when running in high vacuum and that friction coefficient and wear volume increased with increasing normal load. Also at high load conditions, the friction coefficient and wear volume increased with increasing sliding velocity.

• Tribology and Lubricants
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• 제11권3호
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• pp.11-23
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• 1995

The friction and wear behavior of $Al_{2}O_{3}$, SiC, and $Si_{3}N_{4}$ under the different sliding conditions were investigated. The cylinder-on-disc wear tester was used for a wear test method. Using the servo-motor, the sliding speed did not alternate due to the frictional forces. Three kinds of loads were selected to watch the variation of the wear rates and the frictional forces under a constant speed. Three kinds of sliding conditions were used to see the effects of the oxidation and the abrasion. The dominant wear mechanisms of $Al_{2}O_{3}$ were the abrasion and the formation of transfer layers. The abrasion has a great effect on the wear of SiC. The wear of $Si_{3}N_{4}$ was due to the asperity-failure and the oxidation. Also, the wear rate of each ceramic is shown to be related to the frictional power provided to the tribological system.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제30회 추계학술대회
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• pp.219-224
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• 1999

The effects of solid lubricants on wear and friction characteristics of friction materials were studied using a pad-on-disk type friction tester. Friction materials with ten formulations containing different relative amounts of solid lubricants(graphite, MoS$_2$and Sb$_2$S$_3$) were investigated. Results of this work showed that each formulation with different relative amounts of the lubricants had unique friction characteristics. At low brake temperatures, friction materials containing rich graphite showed a small amount of $\mu$ change during sliding. At elevated temperatures, on the other hand, friction materials with rich Sb$_2$S$_3$and graphite showed smaller $\mu$ changes suggesting complementary lubrication of Sb$_2$S$_3$and graphite during sliding. However, the friction materials with rich Sb$_2$S$_3$showed a large amount of wear.

• Elastomers and Composites
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• 제36권2호
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• pp.121-129
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• 2001

다양한 조건 하에서 고무판의 마찰계수를 폭정하기 위하여 수직하중, 미끄럼속도, 경도, 윤활 조건 및 고무판 두께 등을 변화시켜가면서 시험을 실시하였다. 시험에 사용된 고무판의 재질은 천연고무이며, 상대 부품은 강구를 사용하였다. 수직하중과 미끄럼속도는 마찰계수에 현저한 영향을 미치지 않았으며, 고무판의 경도가 높아지고 고무판의 두께가 얇아질수록 마찰계수는 감소하였다. 무윤활 시 마찰계수는 큰 편차를 보였으나, 오일 윤활인 경우 다른 조건에 관계없이 안정된 값을 나타내었다.

• Tribology and Lubricants
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• 제34권6호
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• pp.318-324
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• 2018

This study aims to visualize the friction and wear behaviors of metal coatings in real time. The main mechanism of wear is identified by observing all the processes in which wear occurs. The friction coefficients of the moments are monitored to confirm the relationship between the friction and wear characteristics of the coating. Thin Ag coatings, which are several hundred nanometers in thickness, are prepared by depositing Ag atoms on silicon substrates through a sputtering method. A pin-on-disk-type tribo-tester is installed inside a scanning electron microscope (SEM) to evaluate the friction and wear characteristics of the Ag coating. A fine diamond pin is brought into contact with the Ag coating surface, and a load of 20 mN is applied. The contact pressure is calculated to be approximately 15 GPa. The moments of wear caused by the sliding motion are visualized, and the changes in the friction characteristics according to each step of wear generation are monitored. The Ag coating can be confirmed to exhibit a wear phenomenon by gradually peeling off the surface of the coating on observing the friction and wear characteristics of the coating in real time inside the SEM. This can be explained by a typical plowing-type wear mechanism.

• Tribology and Lubricants
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• 제17권4호
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• pp.267-275
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• 2001

Friction and wear properties of brake friction materials containing different metal fibers (Al, Cu or Steel fibers) were investigated. Based on a simple experimental formulation, friction materials with the same amount of metal fibers were tested using a pad-on-disk type friction tester. Two different materials (gray cast iron and aluminum metal matrix composite (MMC)) were used for disks rubbing against the friction materials. Results front ambient temperature tests revealed that the friction material containing Cu fibers sliding against gray cast iron disk showed a distinct negative $\mu$-v (friction coefficient vs. sliding velocity) relation implying possible stick-slip generation at low speeds. The negative $\mu$- v relation was not observed when the Cu-containing friction materials were rubbed against the Al-MMC counter surface. Elevated temperature tests showed that the friction level and the intensity of friction force oscillation were strongly affected by the thermal conductivity and melting temperature of metallic ingredients of the friction couple. Friction materials slid against cast iron disks exhibited higher friction coefficients than Al-MMC (metal matrix composite) disks during high temperature tests. On the other hand, high temperature test results suggested that copper fibers in the friction material improved fade resistance and that steel fibers were not compatible with Al-MMC disks showing severe material transfer and erratic friction behavior during sliding at elevated temperatures.

• Tribology and Lubricants
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• 제31권4호
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• pp.183-188
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• 2015

This paper presents the experimental effects of lubricant with nanodiamond particles in sliding friction. In order to improve the performance of lubricants many additives are used, such as MoS₂, cadmium chloride, indium, sulfides, and phosphides. These additives are harmful to human health and to the environment, so alternatives are necessary. One such alternative is nanodiamond powder, which has a large surface area. In order to investigate the effect of nanodiamonds in lubricants under sliding friction, they are dispersed in the lubricant at a variety of concentrations (0 wt%, 0.1 wt%, 0.3 wt%, 0.5 wt%, and 1 wt%) using the matrix synthesis method. Friction and wear tests are performed according to the ASTM G99 method using a pin-on-disc tester at room temperature. The specimens used in this experiment are AISI 52100 ball bearings and AISI 1020 steel discs. During the test, lubricant mixed with nanodiamond is supplied constantly to keep the two bodies separated by a lubricant film. To maintain boundary lubrication, the speed is set to 0.18 m/s and a load of 294 N is applied to the disc through the pin. Results are recorded by using workbench software over the test duration of 10 minutes. Experimental results show that when the concentration of nanodiamond increases, the coefficient of friction decreases. However, above a nanodiamond concentration of 0.5 wt%, both the coefficient of friction and wear volume increase. From this experiment, the optimum concentration of nanodiamond showing a minimum coefficient of friction of 0.09 and minimum wear volume of 0.82 nm² was 0.5 wt%.

• Tribology and Lubricants
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• 제25권4호
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• pp.231-235
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• 2009

In this study, the influence of contact pressure on the variation in coefficients of friction between porcine knee joint cartilage and Co-Cr alloy in a repeat pass sliding motion was investigated. Flat-ended cartilage pin specimens(9 mm diameter, 8 mm long) were prepared from porcine(6 months old) knee joints by a drill-type punch. Friction tests were conducted by using a pin-on-disk type friction tester for an hour in PBS lubricated condition under the contact pressures of 0.5, 1 and 2 MPa with 50 mm distance per a cycle at ambient condition. As a result, coefficients of friction increased as the test duration increased for all contact pressures. The maximum coefficients of friction were 0.082, 0.06 and 0.098 for 0.5, 1, and 2 MPa, respectively. It showed that coefficients of friction of porcine knee joint cartilage against Co-Cr alloy depended on the level of contact pressure and related to squeeze film lubrication mechanism.