• Tribology and Lubricants
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• v.13 no.1
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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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.3
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• pp.593-598
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• 2008

It was made a friction material of various kinds by adding 10%, 20% and 30% of reduced iron. It was obtained by a connected-reduced process in a blast furnace sludge and oxidized iron, instead of $BaSO_4$, which is already a used inorganic filling material among a component of a brake friction material. This was done by a basic physical property test, a friction performance test to use a brake dynamometer. Moreover, in case of an add in the friction material, instead of using $BaSO_4$, the more expensive filling material, the reduced iron was also better because it has an excellent a friction property of an exothermic temperature, wear, etc. was 10%. At G1 and G3 specimens, a shear strength and a bonding strength of the friction material was decreased to be able to increase an amount of the blast furnace sludge and the reduced iron, but an application of all friction materials appeared enough strength.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.4
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• pp.313-320
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• 2005

Stick-slip friction is one of the material removal mechanisms in tribology. It occurs when the static friction force is larger than the dynamic friction force, and make the friction curve fluctuated. In the friction monitoring of chemical mechanical polishing(CMP), the friction force also vibrates just as stick-slip friction. In this paper, an attempt to show the similarity between stick-slip friction and the friction of CMP was conducted. The prepared hard pa(IC1000/Suba400 stacked/sup TM/) and soft pad(Suba400/sup TM/) were tested with SiO₂ slurry. The friction force was measured by piezoelectric sensor. According to this experiment, it was shown that as the head and table velocity became faster, the stick-slip time shortened because of the change of real contact area. And, the gradient of stick-slip period as a function of head and table speed in soft pad was more precipitous than that of hard one. From these results, it seems that the fluctuating friction force in CMP is stick-slip friction caused by viscoelastic behavior of the pad and the change of real contact area.

• Tribology and Lubricants
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• v.17 no.4
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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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• v.21 no.2
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• pp.77-82
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• 2005

In previous paper, the wear properties of clutch facing materials with two different copper amounts against fly-wheel materials used in the clutch system were investigated by sliding wear tests at different applied loads and speeds. This paper have been aimed to evaluate the friction properties for clutch facing materials at the same test conditions as the previous paper. The experimental results indicated that the friction properties of clutch facing materials are influenced from the thermal conductivities of the clutch facing material and the counter material. The clutch facing material with the lower thermal conductivity and the fly-wheel material with the higher thermal conductivity showed the low and stable friction coefficient in the range of high sliding speed. This appears to be due to the formation of a film on the surface of the fly-wheel material.

• Tribology and Lubricants
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• v.32 no.2
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• pp.39-43
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• 2016

Magnetorheological elastomers (MREs) are a type of “smart” material, and their properties can be controlled rapidly and reversibly under the influence of an external stimulus. The application of an external magnetic field can change the shear modulus, hardness, and friction coefficient of MREs. The friction can cause vibration; moreover, the vibration can affect friction. The change of friction depends on the relative motion, normal force, roughness of the rubbing surfaces, material type, temperature, lubrication, relative humidity, and vibration condition. As MREs are a type of “smart material,” their friction coefficient can be reduced by applying an external magnetic field—the applications of this feature in engineering have been widely studied. However, the friction properties of MREs under vibration have not been tested to date. In this study, MRE samples and a reciprocating friction tester were fabricated. The friction coefficient was measured to evaluate the friction properties under various vibration conditions; subsequently, the wear depth and wear surface profile of the MRE were observed in order to evaluate the wear properties. The results show that the friction coefficient of the MREs decreased when a magnetic field was applied. Moreover, the friction coefficient decreased when the vibrational amplitudes increased. The wear depth of the MRE also decreased as the vibrational amplitudes increased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.653-654
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• 2005

Stick-slip friction is one of the material removal mechanisms in tribology. This stick-slip friction occurs when the static friction force is larger than the dynamic friction force, and make the friction curve fluctuated. In the friction force monitoring system for chemical mechanical polishing(CMP), the friction force also vibrates just as stick-slip friction. It seems that the stick-slip friction causes scratches on the surface of moving parts. In this paper, A study on the scratches which occur during copper CMP was conducted in a view of stick-slip friction.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.515-518
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• 2006

This paper presents the friction and wear characteristics of contact type sealing unit for a water turbine of a small hydro-power generation, which Is to stop a leakage of a circulating water from a outside of an impeller to an inside of a rolling bearing. The surface wear strongly affect to the seal life of a mechanical face seal. In this study, the hardness of a stainless steel in which is a heat-treated is 892.8 in Vickers hardness and the hardness of silicone carbide of SiC is 714.1 in Vickers hardness. The surface hardness of a heat-treated stainless steel is 25% high compared with that of a ceramic material of SiC. The contact modes of rubbing surfaces aye a dry friction a water film friction and a mixed friction that is contaminated by a dust, silt and moistures, etc. These two factors of a contact rubbing modes and a material property are very important parameters on the tribological performance such as a friction and wear between a seal ring and a seal seat. The experimental result shows that the surface hardness of a seal material is very important on the friction coefficient and a wear volume. Thus, the results recommend higher hardness of a seal material, which may reduce a friction loss and increase a wear life of primary seal components

• Elastomers and Composites
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• v.36 no.1
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• pp.3-13
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• 2001

To resolve environmental problem of waste tire and asbestos and also to capitalize the wastes, we developed a new kind of friction material using scrap tire, potassium hexatitanate, filler, and friction modifier in which rubber made a continuous phase. The material containing 5, 20, 10, 20phr of potassium hexatitanate, phenol, friction modifier, $BaSO_4$, respectively showed good friction properties, high and stable coefficient or friction, and low wear rate.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.265-271
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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 four different 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 lubricants had unique friction characteristics. Friction material containing rich MoS$_2$ showed excellent friction stability at different friction conditions. However friction material containing rich Sb$_2$S$_3$revealed high wear of friction materials.