• Title, Summary, Keyword: Friction

Search Result 7,696, Processing Time 0.051 seconds

FRICTION CHARACTERISTICS OF A PAPER-BASED FRICTION MATERIAL

  • Gao, H.;Barber, G.-C.;Chu, H.
    • International Journal of Automotive Technology
    • /
    • v.3 no.4
    • /
    • pp.171-176
    • /
    • 2002
  • A bench test set-up is employed to simulate the friction characteristics of a paper-based friction material operating against a steel plate. Dry friction tests are run as well as tests with transmission fluids. Glazed friction material produces a negative coefficient of friction versus sliding velocity (f-v) curve for both dry friction and lubrication with transmission fluids. At low sliding speeds, the coefficient of friction when operating in transmission fluids for glazed friction materials is greater than that under dry friction. An appreciable negative f-v slope occurs at low sliding speeds for glazed friction materials when running with the transmission fluid. The friction material after running in produces a constant f-v curve under dry friction and a negative slope when lubricated with transmission fluid. At low sliding speeds, the coefficient of friction of the run-in friction material is lower than that of the glazed wet material. On the other hand, the run-in friction material has a larger friction coefficient than does the glazed friction material at higher sliding speeds.

A Dry Friction Model to Realize Stick for Simulation of the System with Friction and Accuracy Verification of the Friction Model (마찰력이 작용하는 동적 시스템의 점착 구현을 위한 마찰모델 제안 및 정확성 검증)

  • Choi, Chan-Kyu;Yoo, Hong-Hee
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.22 no.8
    • /
    • pp.748-755
    • /
    • 2012
  • Friction causes self-excited vibration, stick-slip vibration and any other friction-induced phenomena. That kinds of vibrations cause chatter and squeal. In order to predict such vibrations accurately, employing an accurate friction model is very important because a dynamic behavior of a system with friction is dominantly governed by a friction model. A Coulomb friction model is the most widely known model. Coulomb friction model is useful model to obtain analytical solutions of the system with friction and the model gives relatively good simulation result. However, defining a friction force at a stick state in simulation is hard because of the characteristic itself and a Coulomb friction model is discontinuous function between a static and a dynamic friction coefficient. Therefore, applying the Coulomb friction model to a simulation is not appropriate. In order to resolve these problems, an approximated Coulomb friction model was developed using simple and continuous function. However, an approximated Coulomb friction model cannot realize stick. Therefore, an approximated Coulomb friction model cannot describe friction phenomena accurately. In order to analyze a friction phenomenon accurately, a friction model for a simulation was proposed in this paper. A proposed friction model realizes stick and gives reasonably good results compared to results obtained by the simulation employing an approximated Coulomb friction model. Accuracy of a proposed friction model was verified by comparing experimental results.

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
    • /
    • v.28 no.3
    • /
    • pp.117-123
    • /
    • 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.

Influence of the Relative Amount of Graphite and Zirconium Silicate on Friction Characteristics (흑연과 지르콘의 상대적인 함량에 따른 마찰특성에 관한 연구)

  • Kim, Seong-Jin;Jang, Ho
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
    • /
    • /
    • pp.166-172
    • /
    • 2000
  • Friction characteristics of phenolic resin-based friction composites containing threedifferent relative amounts of graphite and zirconium silicate were investigated by using a pad-on-disk type friction tester. Constant temperature test and constant interval test at three different initial temperatures(100. 200, 300$^{\circ}C$) were performed to examine the effects of friction heat on friction characteristics at elevated temperature. The friction composite(FMO.7) with higher content of ZrSiO$_4$showed unstable friction force at higher temperature and resulted in larger fluctuations of vibration during friction test. The abrasive action of ZrSiO$_4$in friction composite impeded stable transfer film and induced higher friction heat at friction interface. Friction oscillations according to the temperature were associated with the formation of transfer film(i'd body layer) on the friction composite and the counter part.

  • PDF

A Study on Adhesion Friction Characteristics of Rubber for Tire Tread

  • Oh, Yumrak;Jeon, Seong-hee;Lee, Dong Youm;Kim, Hak-Joo;Kim, Jeong-Heon
    • Elastomers and Composites
    • /
    • v.54 no.4
    • /
    • pp.299-307
    • /
    • 2019
  • Rubber friction properties include adhesion friction characteristics of the interface, hysteresis friction characteristics originating from repeated rubber deformations, and cohesion friction characteristics due to wear and tear. Cohesion friction is generally sufficiently small (< 3%) that it can be ignored, whereas adhesion friction has a relatively large contribution of 15%, but has not been investigated thoroughly. Therefore, through an adhesion friction study, the adhesion mechanism was examined and the relationship between friction characteristics and adhesion friction on dry surfaces was derived. The wet grip characteristics of tread rubber are fully described by the hysteresis characteristics of tires, but friction characteristics on dry roads are difficult to determine without adhesion factors. The results presented herein demonstrate that the combination of hysteresis and adhesion properties in the tread rubber sufficiently explained the characteristics of the dry grip. Based on the results of this study, technologies will be developed to determine the key factors governing adhesion friction characteristics and improve dry tire braking performance.

High temperature Friction and Wear of Friction Material; The Effect of the Relative Amount of Graphite and Zirconium Silicate (ZrSiO$_4$) (흑연과 지르콘의 상대적 함량에 따른 마찰재의 고온 마찰 및 마모특성)

  • Kim, Seong-Jin;Jang, Ho
    • Tribology and Lubricants
    • /
    • v.16 no.5
    • /
    • pp.365-372
    • /
    • 2000
  • Tribological behavior of novolac resin-based friction materials with three different relative amounts of graphite and zirconium silicate was investigated by using a pad-on-disk type friction tester. The goal of this paper is to examine the effects of the relative amount of a lubricant and an abrasive in the automotive friction material on friction and wear characteristics at elevated temperature. Friction and wear of friction materials were affected by the existence of transfer film(3$\^$rd/ body layer) at friction interface and the composition of friction material, especially lubricant amount. The friction material with higher content of graphite indicated homogenized and durable transfer film, and resulted in stable friction coefficient regardless of the increase in friction heat. The experimental result also showed that the higher concentration of ZrSiO$_4$ in friction material aggravated friction stability and wear resistance due to the higher friction heat generated at fiction interface during high temperature friction test.

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
    • /
    • /
    • pp.265-271
    • /
    • 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.

  • PDF

Effect of Humidity on Friction Characteristics of Automotive Friction Materials

  • Kim, Seong-Jin;Lee, Jae-Young;Jang, Ho
    • KSTLE International Journal
    • /
    • v.2 no.2
    • /
    • pp.150-153
    • /
    • 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.

  • PDF

Tribological Characteristics for High Perfomance Metallic Friction Materials (고성능 금속마찰재의 트라이볼로지적 특성)

  • 김석삼;김재호;안효준
    • Tribology and Lubricants
    • /
    • v.14 no.1
    • /
    • pp.45-53
    • /
    • 1998
  • Friction and wear test for two kinds of Cu-based sintered metallic friction material against cast iron disk was carried out by plate-on-disk type friction and wear tester to investigate the friction and wear characteristics of brake system in severe condition. In this experimental study, the counter specimen was cast iron which is being used generally in brakes of heavy duty equipments. Test friction materials were A type which was manufactured by foreign company and B type by domestic company. Friction coefficient and wear volume were measured and compared with each other. The experiment was performed under room temperature. The worn surface of cast iron disk and friction material were observed by scanning electron microscope. The temperature of surface of disk was measured continuously by the non-contacting thermometer. It was found that A type friction material had stable friction coefficient over the wide range of sliding condition, but B type friction material had unstable friction coefficient and lower value of 0.2 under the severe sliding condition.

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
    • /
    • v.13 no.3
    • /
    • pp.10-19
    • /
    • 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.