• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.606-607
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• 2008

Nowadays, noise and vibration phenomena of a disc brake system have been given various names that provide some definitions of sound and vibration emitted such as grind, grunt, moan, squeak, squeal, judder and wire brush. The most common and annoying noise of a disc brake system is squeal noise. It is defined as noise whose frequency content is 1 kHz and higher with excessively high and irrigating sound pressure levels. In this paper, the noise and vibration characteristics of a disc brake system have been investigated to develop the fusion-type friction material, which overcomes the low steel and non-asbestos organic friction materials. For the purpose, both experimental evaluation and complex eigenvalue analysis have been carried out.

• Steel and Composite Structures
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• 제19권4호
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• pp.939-952
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• 2015

In this paper, brake pad performance of two organic matrix composites namely, Sample 1 (contains no brass filler) and Sample 2 (contains 1.5% brass filler), is studied based on tribological and squeal noise behavior. In the first stage, a pin-on-disc tribometer is used to evaluate the frictional behavior of the two pads. On the following stage, these pads are tested on squeal noise occurrence using a drag-type brake dynamometer. From the two type of tests, the results show that; (i) brass fillers play a dual role; firstly as reinforcing element of the brake pad providing primary contact sites, and secondly as solid lubricant by contributing to the formation of a layer of granular material providing velocity accommodation between the pad and the disc; (ii) brass fillers contribute to friction force stabilization and smooth sliding behavior; (iii) the presence of small weight quantity of brass filler strongly contributes to squeal occurrences; (iv) there is close correlation between pin-on-disc tribometer and brake dynamometer tests in terms of tribological aspect.

• 한국소음진동공학회논문집
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• 제20권1호
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• pp.98-105
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• 2010

Squeal, a kind of self-excited vibration, is generated by the friction between the disc and the friction materials. It occurs at the ending stage of the braking process, and radiates and audible frequency range of 1 kHz to 10 kHz. Squeal is generated from unstability because of the coupling between the translation and rotation of the system. This instability is caused by the follower force and follower force is normal component of the friction force. In this paper modal analysis of wheel brake system was performed in order to predict the squeal phenomenon. It was shown that the prediction of system instability is possible by FEM. A finite element model of that brake system was made. Some parts of a real brake was selected and modeled. Modal analysis method performs analyses of each brake system component. Experimental modal analysis was performed for each brake components and experimental results were compared with analytical results from FEM. To predict the dynamic unstability of a whole system, the complex eigenvalue analysis for assembly modeling of components confirmed by modal analysis is performed. The finite element models of the disk brake assembly have been constructed, and the squeal noise problems have been solved by complex eigenvalue analysis. The complex eigenvalue analysis results compared with real train test.

• 한국자동차공학회논문집
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• 제2권5호
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• pp.41-47
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• 1994

An optimal brake pad must have stable friction, low wear and least amount of squeal. In this study, the friction, wear and squeal behavior of some non-asbestos Kevlar materials have been evaluated experimentally. Four specimens with different formulations and a pin-on-disk machine were used for this study. To determine the role of each component in friction and squeal of a brake pad, statistical correlations have been obtained and discussed. The components tested were : Kevlar, Steel Powder, Barium Sulfate and fillers combined by Resin.

• Tribology and Lubricants
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• 제33권1호
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• pp.15-22
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• 2017

Because the running speed of vehicles is increasing and a shorter braking distance is required, high heat-resistant brake pads are needed to satisfy the requirements of customers and car makers. In the near future, hazardous materials such as Cu, Cr, Zn, and Sb will be restricted from use in friction materials. Ceramic composites reinforced by carbon fibers are good candidates for eco-friendly friction materials. In this study, we develop ceramic composite friction materials. The friction materials are composed of carbon fibers, Si, SiC, graphite, and phenol resin and are prepared by hot forming and heat treatment at high temperatures. The density, void ratio, and compressive strength are $1.59-1.66g/cm^3$, 16.6-20, and 70-90 MPa, respectively. Friction and wear tests are performed using a pin-on-plate-type reciprocating friction tester at 25, 100, and $200^{\circ}C$. The counterpart material is a CrMoV steel extracted from a KTX brake disc. Friction coefficient, wear amount, and wear mechanism are measured and examined. We determine that the friction coefficients depend on the temperature and the fluctuation of the friction coefficients is larger at higher temperatures. The amount of wear increases with the surface temperatures of the specimens. The tribological properties of the developed composites are similar to those of a Cu-based sintered friction material. Through this study, it is confirmed that ceramic composite materials can be used as friction materials.

• Journal of Advanced Marine Engineering and Technology
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• 제19권4호
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• pp.51-60
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• 1995

Along with the rapid development of automobile industry in this country the necessity of high quality braking material is ever increased to maintain the comfortness as well as the safety the passengers. Asbestos-based friction materials are banned in the developed countries because of their cancer-inducing effect. This study focuses on the development of non-acbestos friction material with acceptable properties such as wear resistant high temperature endurant and low-noise enducing. We have all the intermediate test results indicating the contribution of each additives. These are qualitatively analyzed. Manufacturing processes such as opening of the kevlar and degasing at elevated temperature is equally important to attain proper level of friction quality.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1000-1004
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• 2007

Thermal cracks are among the key factors that control the quality of a brake disk. Thermal cracks may shorten the lifetime of the disc and increase brake noise. Therefore, high heat-resistant brake disk materials are needed. In this study, three kinds of disk material were tested. They are composed of C, Si, Mn, P, S, Cu, Cr, Mo, and Ni. For the three materials, tensile tests, hardness measurement, metallurgical structure analysis, image analyzer analysis, etc were carried out. And friction tests were performed by a small scale dynamometer.

• KSTLE International Journal
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• 제2권2호
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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.

• 한국철도학회논문집
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• 제20권1호
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• pp.1-10
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• 2017

제동 스킬소음은 승객과 선로 주변의 주민에게 불편을 끼쳐 시급히 해결해야 할 문제의 하나이지만 해결책을 찾는 것은 쉽지 않다. 제동 스킬소음을 저감하기 위한 해결책은 크게 제동 마찰재의 소재를 개량하거나 제동패드의 구조를 개선하는 것으로 구분할 수 있다. 본 연구에서는 현재 KTX 차량에 사용되고 있는 제동패드를 기준으로 마찰재의 소재만을 바꾼 패드와, 동일한 마찰재 소재를 사용하지만 구조를 유연형으로 바꾼 제동패드를 제작하여 제동 다이나모미터에서 다양한 조건으로 마찰특성과 소음특성을 평가하고 영업차량이 역에 정차할 때 측정한 스킬소음과 비교 및 분석하였다. 제동 다이나모미터 시험이 실차 시험을 어느 정도 재현하는 것이 가능한다는 것을 발견하였고, 영업열차에서 최고 스킬소음이 발생한 4,500Hz 대역의 스킬소음은 다이나모미터 시험에서도 정확히 일치하고, 이 주파수는 제동디스크의 고유진동수와 일치하는 것을 규명하였다. 제동 스킬소음이 발생하는 주파수는 캘리퍼에 작용하는 압력, 시험온도, 그리고 제동 초속도에 따라 달라지지만 일정한 경향을 보여주지는 않았다. 개발된 제동패드의 평균 마찰계수는 0.35~0.45의 범위에 있고 마찰재 소재만을 바꾼 경우는 21.6dB(A), 구조를 변경한 경우는 17.3dB(A) 만큼 최대 소음을 줄일 수 있었다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.332-340
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• 2000

Friction properties of automotive brake pads containing different types of abrasivess were investigated. Five different abrasives, including o-quartz, magnesia, magnetite, alumina, zircon, were employed in this investigation and size effects of the abrasives on friction characteristics were also studied using 1, 50, 140$\mu\textrm{m}$ size zircon. Experimental results showed that the hardness and size of these abrasive particles were strongly related to friction behaviors and wear mechanisms. Harder and smaller abrasives showed higher friction coefficient and more wear. The surfaces of friction materials with different sizes of abrasives showed that two different modes of abrasion (two-body and three-body abrasion) appeared during sliding. Considering the above results, abrasive materials were thought to destroy transfer film and the extent of the destruction depends on the types and sizes of abrasive particles. A mechanism of the wear mode transition (two-body to three body abrasive motion) was suggested considering the binding energy and friction energy in terms of abrasive particle size.