• Title, Summary, Keyword: Friction Materials

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Tribological Properties of Hybrid Friction Materials: Combining Low-steel and Non-steel Friction Materials (금속계와 유기계 마찰재의 분포에 따른 하이브리드 마찰재의 마찰 특성)

  • Kim, JinWoo;Jang, Ho
    • Tribology and Lubricants
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    • v.28 no.3
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    • pp.117-123
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    • 2012
  • Tribological properties of hybrid type friction materials were studied. Hybrid friction materials were produced by combining non-steel(NS) and low-steel(LS) type friction materials. The emphasis of the investigation was given to possible synergistic effects from the two different friction materials, in terms of friction stability at high temperatures and the amplitude of friction oscillation, also known as stick-slip at low sliding speeds. The high temperature friction test results showed that the friction effectiveness of the hybrid friction material was well sustained compared to LS and NS friction materials. Wear resistance of the hybrid type was similar to LS friction materials. Examination of the rubbing surfaces after tests revealed that the friction characteristics of the hybrid friction material were attributed to the wear debris produced from low-steel friction materials, which were migrated to the surface of the non-steel friction material, forming new contact plateaus. The stick-slip amplitude and its frequency were pronounced when non-steel friction material was tested, while hybrid and low-steel types showed relatively small stick-slip amplitudes. These results suggest possible improvement of tribological properties by designing a hybrid composite of low-steel and non-steel friction materials.

Study of Friction Charactedstics of Non-asbestos Organic (NAO) and Semi-metallic Brake Pads During Automotive Braking (자동차 제동시 나타나는 마찰재의 마찰 특성에 관한 연구 (II. 비석면계 유기질 (Non-asbestos Organic) 마찰재와 반금속 (Semi-metallic) 마찰재의 마찰 특성 비교))

  • Kim, Seong-Jin;Jang, Ho
    • Tribology and Lubricants
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    • v.13 no.3
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    • pp.10-19
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    • 1997
  • Frictional characteristics of two different types of automotive friction materials were studied. They were non-asbestos organic and semi-metallic friction materials. The two friction materials were tested using an inertial brake dynamometer to investigate friction stability, rooster tailing phenomena, temperature change during drags and stops. Results show that the level of the friction force is strong functions of time, temperature, and speed regardless of the type of friction materials. In particular, rooster tailing effects are pronounced in the case of semi-metallic friction materials compared to non-asbestos organic friction materials. The phenomena appear strongly dependent on raw materials contained in the friction materials.

Effect of Humidity on Friction Characteristics of Automotive Friction Materials

  • Kim, Seong-Jin;Lee, Jae-Young;Jang, Ho
    • KSTLE International Journal
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    • v.2 no.2
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    • pp.150-153
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    • 2001
  • The effects of humidity on friction performance of automotive brake materials were studied using a pad-on-disk type friction tester. Three different friction materials based on a simple formulation were investigated by changing the solid lubricant graphite, MoS$_2$, and Sb$_2$S$_3$. Friction materials without solid lubricants were also examined to study the effect of other ingredients in the matrix on humidity. The friction material containing graphite was strongly affected by the humidity showing lower friction coefficient at high humidity level than other conditions. On the other hand, the friction material containing MoS$_2$exhibited higher friction coefficient at initial stage under high humidity level. The friction material without solid lubricant or with Sb$_2$S$_3$ was not affected by humidity conditions. However, the friction material containing barite showed strong speed dependence.

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A Study of Binder Resins and Reinforcing Fibers in Automotive Friction Materials on Friction and Wear (자동차용 마찰재에 사용되는 결합제와 강화섬유에 따른 마찰 및 마모특성에 관한 연구)

  • Kim, Seong-Jin;Jang, Ho
    • Tribology and Lubricants
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    • v.15 no.4
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    • pp.314-320
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    • 1999
  • Friction and wear characteristics of phenolic resin-based friction materials reinforced with aramid pulp and potassium titanate were investigated using a pad-on-disk type friction tester. Friction characteristics such as friction stability, thermal stability, and wear rate varied according to the type of phenolic resins and the relative amount of aramid pulp and potassium titanate. The modified novolac resin-based friction materials showed better heat resistance and friction stability than those with the unmodified(straight) novolac resin. Compared with friction materials filled with potassium titanate or aramid pulp only, the friction materials reinforced with both aramid pulp and potassium titanate showed good friction stability and wear resistance. Increment of aramid pulp from 10 to 20 vol.% however, showed little difference in friction stability.

Effects of the Phenolic Resins in the Automotive Friction Materials on Friction Characteristics (자동차용 마찰재에 사5되는 폐놀수지의 종류에 따른 마찰특성의 영향에 관한 연구)

  • Kim, Seong-Jin;Hong, Young-Suk;Jang, Ho
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.92-100
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    • 1999
  • Friction characteristics of automotive friction materials according to the types of phenolic resin were investigated by using a pad-on-disk type friction tester. Four different simplified friction materials bound with Bakelite$^{TM}$ and Xylok$^{TM}$ phenolic resin were studied in this work. Two different modes of drag test(constant initial temperature test and constant interval test) were employed to analyze the effects of the binders on friction characteristics. Friction materials containing modified Xylok$^{TM}$ resin showed good heat resistance and friction stability. The results also showed that aramid fiber played important roles in improving friction stability and weard wear

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Investigation of Friction and Wear Characteristics of Automotive friction Materials containing different relative amounts of solid lubricants(Graphite, MoS$_2$, and Sb$_2$S$_3$) (자동차용 마찰재에 사용되는 고체윤활제의 성분비에 따른 마찰 밀 마모 특성에 관한 연구)

  • Choi, Nak-Cheon;Jang, Ho
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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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.

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Tribology of friction materials containing different metal fibers (마찰재에 함유된 금속섬유의 종류에 따른 마찰 특성)

  • Ko, Kil-Ju;Jang, Ho
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.55-63
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    • 2001
  • Friction and wear properties of brake friction materials containing different metal fibers (Al, Cu or Steel fibers) were investigated using a pad-on-disk type friction tester. Two different materials(gray iron and Al-MMC)) were used for disks rubbing against the friction materials. Results from ambient temperature tests revealed that the friction material containing Cu fibers sliding against cast iron disk showed a distinct negative ${\mu}$-ν (friction coefficient vs. sliding velocity) relation implying possible stick-slip generation at low speed. The negative ${\mu}$-ν relation was not observed when the Cu-containing friction materials were rubbed against the. Al-MMC counter surface. As applied loads increased, friction materials showed higher friction coefficients comparatively. Friction materials slid against cast iron disks exhibited higher friction coefficients than Al-MMC 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 the steel fibers were not compatible with Al-MMC disks showing severe material transfer and erratic friction behavior during sliding at elevated temperatures.

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Friction Characteristics of Non-Asbestos Organic (NAO) and Low-Steel Friction Materials: The Comparative Study

  • Kim, Seoun Jin;Jang, Ho
    • KSTLE International Journal
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    • v.1 no.1
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    • pp.1-7
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    • 2000
  • Eviction characteristics of two typical friction materials (non-asbestos organic and low-steel friction materials) for an automotive brake system were investigated using an inertial brake dynamometer. In particular, the effect of sliding speed on friction coefficient was carefully investigated employing various test modes. The two friction materials were developed for commercial applications and were different mainly in the type and the amount of metallic ingredients in the friction material. The dynamometer test showed that the low-steel friction material was sensitive to the sliding speed exhibiting a negative $\mu$-v relation. On the other hand, the non-asbestos organic friction material was less sensitive to the sliding speed. The low steel friction materials with a negative $\mu$-v relation also induced larger vibration amplitude during brake applications.

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Study of Tribological Characteristics Between Metallic Friction Materials and Brake Disk (금속계 마찰재와 제동디스크 간의 마찰특성 연구)

  • Kim, Sang-Ho;Lee, Hi-Sung
    • Journal of the Korean Society for Railway
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    • v.12 no.1
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    • pp.72-80
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    • 2009
  • The tribiological characteristics such as friction coefficient, friction stability, wear rate and braking temperature between various types of metallic friction materials and heat resistant steel disk, were investigated by using lab-scale dynamometer. Friction materials for high speed train have higher friction coefficient and friction stability as compared to aircraft friction materials even though friction materials for high speed train have lower wear rate. In addition. Cu-matrix friction materials have higher temperature increase rate than Fe-matrix friction materials. All friction surfaces have Fe-base oxide layer after completing test.

Tribological Properties of Semi-metallic Brake Friction Materials Containing Different Solid Lubricants: Graphite, $WS_2$, and $MoS_2$ (고체 윤활제의 특성에 따른 반금속계 마찰재의 마찰 마모특성에 관한 연구)

  • Jang, Ho;Shin, Min-Wook;Kim, Yun-Cheol;Chung, Dong-Yoon
    • Tribology and Lubricants
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    • v.25 no.1
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    • pp.61-65
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    • 2009
  • Tribological properties of the semi-metallic friction materials containing different solid lubricants (graphite, $WS_2$, $MoS_2$) were investigated. The friction materials were fabricated with an experimental formulation and tested with gray cast iron disks. Results showed that graphite contributed to stabilize the friction coefficient during run-in processes. Also, graphite provided better fade resistance than that of $WS_2$ and $MoS_2$. At intermediate temperature ranges, however, friction materials with $WS_2$ or $MoS_2$ maintained higher friction effectiveness than that of graphite. On the other hand, friction materials containing $MoS_2$ showed increased wear rates than that with graphite or $WS_2$. Friction materials with proper combinations of two solid lubricants showed better friction and wear properties than that of the friction materials containing single solid lubricant.