• 한국산업융합학회 논문집
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• 제8권3호
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• pp.135-141
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• 2005

The static friction coefficients of 4 samples against each different temperatures were similar values. Compared against RT, at $80^{\circ}C$ the static friction coefficients decreased from 0.130 to 0.116 that was equal from 88% to 90% of the static friction coefficients respectively. Otherwise the dynamic friction coefficients compared against RT, decreased from 0.138 to 0.088 which was from 71% to 77.5% respectively at $80^{\circ}C$. The noise characteristics were judged by s/d value. And when the s/d value was limited less than 0.8, noise concerns were released. At 3000 engaging cycles the static friction and the dynamic friction coefficient were 0.137 and 0.073 respectively. When plate pressure rose up to $195kg_f/cm^2$, the static friction coefficient decreased from 0.137 to 0.125 but this decreasing could be considered as stable. When speed rose up to 2200rpm, the static friction coefficient decrease from 0.14 to 0.13 but this decreasing could be considered as stable. At 3000 engaging cycles the amount of worn out was 0.04 : the thickness of disc was decrease from 4.72mm to 4.68mm. But regarding the normal operation condition, further more worn-out could not be expected. Therefore concerning worn-out, the basic oil could be considered as appropriate.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제31회 춘계학술대회
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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.

• 대한기계학회논문집A
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• 제27권1호
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• pp.88-93
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• 2003

The aim of this paper is to investigate the friction characteristics of piston assembly, which composed of ring pack and piston skirt. The friction force of piston assembly was measured by using the movable liner in the single cylinder engine, and the various parameters were tested. The friction force was suddenly increased at the expansion stroke due to higher cylinder pressure. The viscous friction was dominant at the mid stroke, but the boundary friction was dominant at the top and bottom dead centers. Through the experiment, we could validate previous theoretical study, and confirm that th e radial clearance and ring tension were very effective to reduce friction loss of piston assembly.

• 한국소음진동공학회논문집
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• 제23권5호
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• pp.423-430
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• 2013

The characteristics of friction noise due to the friction-velocity curve is experimentally investigated through the pin-on-disk setup. The rotation speed of the disk is controlled in order to produce the sliding speed variation. Then, the friction coefficient and the corresponding friction noise are simultaneously measured with respect to the sliding speed between the steel disk and aluminum pin. The experimental results show that the negative friction-velocity slope is essential in generating friction noise.

• Tribology and Lubricants
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• 제15권2호
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• pp.193-198
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• 1999

Applying design methodology, new type friction tester has been developed. Functional analysis has been executed and functional structure were constructed during the conceptual design. Optimal solution has been selected and a proto model has been manufactured according to the conceptual design. Using the tester developed in the laboratory, frictional characteristics of natural rubbers have been experimentally analyzed. Friction coefficient has been calculated from the measured normal force and friction force under various speeds, loads, and temperatures. The corelations between the various operating conditions and friction coefficients have been verified. Especially, drag friction due to the visco-elastic behavior of the rubber has been observed in this analysis.

• Tribology and Lubricants
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• 제17권4호
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• pp.307-311
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• 2001

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.

• Tribology and Lubricants
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• 제13권1호
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• pp.34-41
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• 1997

Frictional behavior of three automotive friction materials (brake pads) containing different amounts of antimony trisulfide ($Sb_2S_3$) and zirconium silicate ($ZRSiO_4$) were investigated using a front brake system. The friction materials were tested on a brake dynamometer (dyno) with gray cast iron rotors. The dynamometer(dyno) test simulated the dragging of a ehicle maintaining 70 km/h and vehicle stops from 100 km/h using 20 different combinations of initial brake temperature (IBT) and input pressure (IP). The results showed a strong influence of the relative amount of $Sb_2S_3$ and $ZrSiO_4$ in friction materials on friction characteristics. Friction stability was improved with the higher concentration of $Sb_2S_3$ in the friction material. Torque variation during drag cycle was increased with an increase of the $ZrSiO_4$ concentration in the friction material. Average friction coefficient and the wear rate of the friction material increased by using more aggressive friction materials containing more $ZrSiO_4$ and less $Sb_2S_3$. Generation of the disk thickness variation (DTV) increased when friction materials with higher concentration of $ZrSiO_4$ were used Careful examination of DTV change showed that aggressiveness of the friction material played an important role in determining torque variation.

• Tribology and Lubricants
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• 제31권2호
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• pp.50-55
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• 2015

This study investigates the effects of a pattern of 200 μm dimples in a hexagonal array on tribological characteristics. A textured surface might reduce the friction coefficient and wear caused by third-body abrasion and thus improve the tribological performance. There are three friction conditions based on the Stribeck curve: boundary friction, mixed friction, and fluid friction conditions. In this experiment, we investigate the friction characteristics by carrying out the friction tests at sliding speeds ranging from 0.06 to 0.34 m/s and normal load ranging from 10 to 100 N. We create dimple surfaces for texturing by using the photolithography method. There are three kinds of specimens with different dimple densities ranging from 10% to 30%. The dimple density on the surface area is the one of the important factors affecting friction characteristics. Friction coefficient generally decreases with an increase in the velocity and load, indicating that the lubrication regime changes depending on the load and velocity. The fluid friction regime is fully developed, as indicated by the duty number graph. Fluid friction occurs at a velocity of 0.14-0.26 m/s. The best performance is seen at 10% dimple density and 200 μm dimple circle in the hexagonal array.

• 한국철도학회논문집
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• 제12권1호
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• pp.72-80
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• 2009

소형 다이나모 시험기를 이용하여 4종류의 금속계 소결마찰재와 내열합금 디스크간의 마찰특성을 평가하였다. 고속철도용 소결마찰재는 항공기용 소결마찰재 보다 높은 마찰계수와 마찰계수 안정성을 나타내며, 마모량도 적었다. 또한, 동합금 기지 마찰재는 철계 기지 마찰재보다 마찰면의 온도가 급격히 상승하면 냉각도 빨리 이루어졌다. 시험 후 모든 마찰면에서 Fe 기지의 산화피막이 형성되었고, 산회피막에 따라 마찰특성이 달라졌으며, 마찰면에서는 정상마 모분이 일부가 마찰면 단차부에서 트랩되는 것을 확인하였다.

• Tribology and Lubricants
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• 제35권6호
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• pp.389-395
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• 2019

In various industries, thin film coatings are used to improve friction and wear characteristics. Various types of tribotesters are used to evaluate the friction and wear characteristics of such thin film coatings. In this study, we fabricated a micro-tribotester and Tribo-scanning electron microscopy (SEM) to compare the friction and wear characteristics of copper (Cu) coatings under an atmospheric pressure and a vacuum condition, respectively. The reliability of the different types of tribotesters was evaluated by performing calibrations for the sensor to measure the friction forces and normal loads. Using the two different types of devices, the friction and wear tests are conducted at the same experimental conditions excluding environment conditions such as the atmospheric pressure and vacuum condition. The friction coefficient at the vacuum condition is lower than at the atmospheric pressure. This difference in friction characteristics is due to the fact that wear phenomena occur differently according to the atmospheric pressure and vacuum condition. At the atmospheric pressure, the abrasive wear is the main wear mechanism. At the vacuum condition, the adhesive wear is the main wear mechanism. The reason for the difference in the wear mechanism of the Cu coating at the atmospheric pressure and the vacuum condition is that the oxidation phenomenon, which does not appear at the vacuum condition, occurs at the atmospheric pressure; therefore, the characteristics of the Cu coating change accordingly.