• Title/Summary/Keyword: brake pad

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A Study on the Effects of Cross-sectional Dimension Change of Brake Pad Specimen on the Uncertainty of the Compressive Strength (제동 패드의 압축강도시편의 단면치수변화가 압축강도 불확도에 미치는 영향 분석)

  • Park, Soo Hong;Park, Jin Kyu;Kim, Si Wan;Park, Chan Kyoung
    • Journal of the Korean Society for Railway
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    • v.17 no.4
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    • pp.223-227
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    • 2014
  • The brake pad is one of the basic brake elements of a railway vehicle. It accomplishes braking action by friction between a pad and a brake disc. Because the brake pad must endure specified high pressure, the compressive strength is managed as the main performance factor. The standards for measuring the compressive strength of brake pads are KRS, KRCS, and KRT. These standards specify the size of the test piece for measuring compressive strength as $20mm{\times}10mm{\times}15mm$ ($W{\times}D{\times}H$). To reduce the uncertainty of the compressive strength, factors of uncertainty were analyzed. The results show that changing the dimensions of the cross section was useful to reduce the uncertainty. The uncertainty due to the new cross-sectional dimension shows the effectiveness of reducing uncertainty.

Robust Wheel Slip Control for Brake-by-Wire System (Brake-by-Wire 시스템을 위한 강인한 휠 슬립 제어)

  • Hong Daegun;Huh Kunsoo;Kang Hyung-Jin;Yoon Paljoo;Hwang Inyong
    • Transactions of the Korean Society of Automotive Engineers
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    • v.13 no.3
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    • pp.102-109
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    • 2005
  • Wheel-slip control systems are able to control the braking force more accurately and can be adapted to different vehicles more easily than conventional ABS systems. But, in order to achieve the superior braking performance through the wheel-slip control, real-time information such as the tire braking force is required. For example, in the case of EHB (Electro-Hydraulic Brake) systems, the tire braking force cannot be measured directly, but can be approximated based on the characteristics of the brake disk-pad friction. The friction characteristics can change significantly depending on aging of the brake, moisture on the contact area, heat etc. In this paper, a wheel slip The proposed wheel slip control system is composed of two subsystems: braking force monitor and robust slip controller In the brake force monitor subsystem, the tire braking forces as well as the brake disk-pad friction coefficient are estimated considering the friction variation between the brake pad and disk. The robust wheel slip control subsystem is designed based on sliding mode control methods and follows the target wheel-slip using the estimated tire braking forces. The proposed sliding mode controller is robust to the uncertainties in estimating the braking force and brake disk-pad friction. The performance of the proposed wheel-slip control system is evaluated in various simulations.

An Experimental Study on the Squeal Noise Generation due to Dynamic Instability of Brake Pad (브레이크 패드의 동적 불안정성에 따른 스퀼 소음 발생 원인의 실험적 연구)

  • Cho, Sangwoon;Lim, Byoungduk
    • Transactions of the Korean Society of Automotive Engineers
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    • v.24 no.5
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    • pp.520-526
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    • 2016
  • Squeal noise is a typical brake noise that is annoying to both passengers and pedestrians. Its frequency range is fairly wide from 1 kHz to 18 kHz, which can be distressful to people. The brake squeal noise occurs due to various mechanisms, such as the mode coupling of the brake system, self-excited vibration, unstable wear, and others. In this study, several parameters involved in the generation of a squeal noise are investigated experimentally by using a brake noise dynamometer. The speed, caliper pressure, torque, and friction coefficient are measured as functions of time on the dynamometer. The contact pressure and temperature distributions of the disc and the pad are also measured by using a thermal imaging camera and a pressure mapping system. As a result of the simultaneous measurement of the friction coefficient and squeal amplitude as functions of the velocity, it is found that the onset of the squeal may be predicted from the ${\mu}-v$ curve. It is also found that a non-uniform contact pressure causes instability and, in turn, a squeal. Based on the analysis results, design modifications of the pad are suggested for improved noise characteristics.

An Experimental Study of Thermoelastic Instability in Automotive Ventilated Disk Brake (통풍식 자동차 디스크 브레이크의 열탄성 불안정성에 관한 실험적 연구)

  • 조병수;백병준;박복춘;김종환;김완두
    • Tribology and Lubricants
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    • v.13 no.4
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    • pp.10-17
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    • 1997
  • The present study describes an experimental investigation of temperature fluctuations associated with thermal instability. Surface temperatures of brake disk and pad were monitered at various locations in a caliper type brake system during drag braking conditions. It was found that the thermal instability appeared in pad more seriously than in disk. The temperatures at various circumferential positions fluctuate synchronously, whereas the center temperature fluctuates with 180$^{\circ}$ phase difference from the outer and inner radius temperatures. The temperature and amplitude of the temperature perturbations are increased due to the increase of contact area in the center location. It was also found that the thermal instability was dominantly determined by the increase of rotation speed and pressure. And the modification of ventilation path could retard the onset of thermal instability.

A Study on Thermal Behavior and Stress Characteristics of Discs under Braking Conditions for Automobiles (자동차 브레이크 제동시 디스크의 열적거동 및 응력 특성에 관한 연구)

  • Baek, Il-Hyun
    • Tribology and Lubricants
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    • v.28 no.5
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    • pp.246-251
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    • 2012
  • Disc brakes and brake linings are part of the braking system in automobiles; this system works due to the braking power between the disc and pad. Vehicle braking systems have complex environments due to the geometry of the disk and pad, the material properties, the braking conditions, etc. Braking energy is converted into thermal energy during the braking process, due to the frictional heat between the disc brake and pad. This heat is changed to a heat flux, which affects the thermal stress of the disc. The purpose of this study was to use the fluid dynamics software ANSYS CFX to investigate the inner flow characteristics of the air and the heat transfer of the disc, and to analyze the effects on the thermal stress of the disc brake.

Study on Development of Flexible Pad for High Speed Train Disk Brake (고속철도 디스크 브레이크의 유연 패드 개발에 대한 연구)

  • Lee, Min-Gyu;Kim, Joo-Yong;Kim, Jae-Min;Yang, Young-Min;Kim, Sang-Ho;Cho, Chong-Du
    • Journal of the Korean Society for Railway
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    • v.14 no.2
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    • pp.100-108
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    • 2011
  • This paper investigates the structural stability and reliability on improving performance of flexible brake pad used in high speed train. To this end, an improved model of flexible pad was obtained through structural analysis. Brake pad specimens were subjected to modal, stroke and endurance tests to examine the dynamic characteristics and mechanical stability. The hot spot generation with increasing rotational speed was observed on chassis dynamometer equipment and then the structurally uniform contact between the disc and pad was achieved. The temperature distribution of flexible pad was measured using the infrared camcorder. Hence, the proposed flexible pad showed the better structural stability and thermal energy emission.

Design for Yaw Brake System in Wind Turbine (풍력발전기 요 브레이크 시스템의 설계)

  • Park, Jin-Hwan;Park, Sang-Shin;Yoon, Yong-Ik;Yoo, Chang-Hee;Hwang, Jung-Gyu
    • Tribology and Lubricants
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    • v.27 no.4
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    • pp.204-208
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    • 2011
  • Yaw brakes are used in wind turbines to control the orientation of blades to be perpendicular to the wind. These devices are very important machine elements because they are closely related to the overall efficiency of wind turbines. One unit of yaw brakes is composed of a friction pad and a caliper. In this study, a tangential force between the friction pad and the disk is calculated when the brake is acting in 750 kW wind turbine. Then, stress distribution and the deformation of the caliper are calculated using a finite element analysis. An experimental equipment is also developed to verify the exactness of calculated results. The analytical and experimental results are presented and discussed.

Thermal Stress Characteristics of a Disk Pad in High-Speed Trains (고속 전철에서 디스크 패드의 열응력 특성에 관한 연구)

  • 김청균;조승현
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1997.10a
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    • pp.245-255
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    • 1997
  • The thermal characteristics of a disk such as temperature distribution, thermal behaviours and thermal stress during a braking operation has been analyzed for a high-speed train using the finite element method. The maximum stress for a pad loaded against a disk was occurred at the trailing and leading edges of the disk pad at the underlayer-backplate interface. The FEM results indictate that the thermal characterisics of the spot type pad shows good performance compared with those of the flat type pad. Thus, the spot type pad in brake system may be recommended for the high-speed train system.

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Unstable Brake Pad Mode Due to Friction-velocity Slope (마찰 곡선에 의한 불안정 브레이크 패드 모드 해석)

  • Nam, Jaehyun;Kang, Jaeyoung
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.22 no.12
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    • pp.1206-1212
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    • 2012
  • The brake squeal propensity due to the friction-velocity curve is numerically investigated. The finite element models for the disc and pad are correlated with the modal test. In the friction-engaged system modeling, the friction function is linearized at the equilibrium. The damping term induced by friction-velocity slope is incorporated into the equations of motion. In the complex eigenvalue analysis, it is found that the pad shear mode is very sensitive to the friction curve. The results shows that the squeal propensity of the pad shear mode can be controlled by the design parameters such as pressure and stiffness.

The Study on the Influence of Pad Wear on Brake Squeal Analysis (브레이크 스퀼 해석에서 패드 마모의 영향에 관한 연구)

  • Lee, Ho-Gun;Son, Min-Hyuk;Seo, Young-Wook;Boo, Kwang-Seok;Kim, Heung-Seob
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.32 no.11
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    • pp.930-936
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    • 2008
  • This paper studies the effect of pad at initial stage and wear during braking on the dynamic contact pressure distribution. Wear is influenced by variable factor (contact pressure, sliding speed, radius, temperature) during dynamic braking and variation in contact pressure distribution. Many researchers have conducted complex eigenvalue analysis considering wear characteristic with Lim and Ashby wear map. The conventional analysis method is assumed the pad has smooth and flat surfaces. The purpose of this paper is to validate that wear rate induced by braking is considered for the precise squeal prediction. After obtaining pad wear from experiment, it is incorporated with FE model of brake system. Finally, the comparisons in fugitive nature of squeal will be carried out between the complex eigenvalue analysis and noise dynamometer experiment.