• Tribology and Lubricants
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• v.17 no.5
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• pp.358-364
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• 2001

Disk brake system transforms a large amount of kinetic energy to thermal energy in a short time. As the size and speed of automotive increases in recent years, the disk brakes absorbs more thermal energy. And this thermal energy can cause an unacceptable braking performance due to the high transient temperature, that is attained at the friction surface of brake disk and pad. Although these high temperatures are one of the biggest problems. In this study, the overall thermal behavior of ventilated disk brake system was investigated by numerical method. The 3-Dimensional unsteady model was simulated by using a general purpose software package “FLUENT” to obtain the temperature distributions of disk and pad. The model includes the more realistic braking method, which repeats braking and release. The effects of several parameters such as the repeated braking, inlet air velocity and thermal conductivity on the temperature distribution were investigated.

• Tribology and Lubricants
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• v.22 no.3
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• pp.149-154
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• 2006

This paper presents the braking friction and wears on the rubbing surfaces of a friction pad-disk brake. In this study, four friction disk specimens are sampled from unused and used disks in which are taken from the disk brake system when the friction induced vibration and noise problems have been occurred during a braking period at a running period of 10,000 km, 20,000 km, and 30,000 km in random. The experimental results indicate that the tribological characteristics of an unused disk brake shows equal and stable as a friction coefficient and temperature distributions during a braking friction/wear test period including a total friction mode from the start to running periods. But the used disk brake shows unstable and uneven friction modes between an outside and inside rubbing surfaces of a disk brake in terms of a friction coefficient and wears. This may lead to a friction induced friction vibration and noise problems of a used disk brake.

• Journal of Digital Convergence
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• v.13 no.11
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• pp.171-178
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• 2015

The disk cover is installed to protect brake disk and calliper and it's removed right before delivering to customers. The temperature of disk cover was measured driving test vehicles(2000cc, diesel) in this study. The highest temperature measured for the driving test(120km/h-braking(0.3G)-stop-120km/h-braking(0.5G)-stop) was $260{\sim}270^{\circ}C$ in the upper part of the disk cover and the temperature varied considerably around the disk cover. It can be inferred from this temperature distribution around the cover that the major heat transfer from hot disk to cover was through convection. In other words, the hot air generated by braking friction moved up to the upper part of the disk cover. And only the upper area of the disk cover was melted down during this driving test. The thickness of disk cover was increased to 1.0mm from 0.7mm and 1 paper of masking tape was pasted in the upper region of the disk cover. Then the cover endured the heated air formed by braking friction during the driving test.

• Tribology and Lubricants
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• v.18 no.6
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• pp.384-388
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• 2002

The adequate design of a passenger car braking system, which is directly related to the safety of a car, is very important since the safety is an essential design parameter of a car to keep men and car from the damage. The thermal behaviors of the ventilated disk has been investigated based on the air cooling effects during repeat braking operations. In this study, the thermal behavior of ventilated disk brake system was investigated by numerical method. The 3-Dimensional unsteady model was simulated by using a general purpose software package “FLUENT” to obtain the temperature distributions of disk and pad. The model includes the more realistic braking method, which repeats braking and release. The effects of aspect ratio of ventilated hole on the heat dissipation was investigated.

• Transactions of Materials Processing
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• v.17 no.6
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• pp.407-411
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• 2008

A brake system in automobile is one of the important parts that directly affect the safety of passengers. Particularly, disk brake module is applied to almost all kinds of automobile brake system due to its remarkable braking power and braking distance. In the disk brake module of an automobile, the bolt for tire wheel is assembled to the disk brake hub by interference fit(bolt pressing process). The process induces small deformation whose range is within tens of ${\mu}m$ and this deformation may cause the runout badness of the whole disk brake module, and even braking problems such as judder or squeal phenomena which makes the loss of braking efficiency. In this study, bolt pressing fit into hub was simulated by $ANSYS^{TM}$, a commercial structure analysis program. Also, the aspect and the cause of hub displacement were analyzed and the solution for decreasing runout of hub was proposed.

• Tribology and Lubricants
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• v.19 no.5
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• pp.268-273
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• 2003

This paper presents hot spot behaviors on the rubbing surface of disk-pad type brake by using coupled thermal-mechanical analysis technique. The height of micro-asperity on the rubbing surface is usually 2∼3 ${\mu}$m in practical disk brakes. Non-uniform micro-contacts between the disk and the rigid friction pads lead to high local temperature distributions, which may cause the material degradation, and develop hot spots, thermal cracks, and brake system failure at the end for a braking period. The friction temperatures on the rubbing surface of disk brakes in which are strongly related to the hot spot and thermal related wears are rapidly concentrated on the micro-contact asperities during braking. The computed FEM results show that the contact stress, friction induced temperature and thermal strain are highly concentrated on the rubbing micro-contact asperities even though the braking speed and force are small during the braking period. This hot spot may directly produce the slippage and various thermal wears on the brake-rubbing surface.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.4B no.2
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• pp.59-64
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• 2004

Study of an accurate and robust braking control method is required as a technical improvement to the servo system. In particular, the braker exhibiting constant braking performance under speed variation conditions of the prime mover needs to be investigated. In this paper, the braking torque of the eddy current braker between the electromagnet stator and rotating disk is analyzed. The torque-speed characteristics and accurate disk construction are represented. From the computer simulation results, it was found that eddy current braking torque is linear or approximately constant over the desired speed range depending on the rotor material, disk construction, pole number and pole displacement of the stator. These relations are confirmed by experimental results.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1761-1765
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• 2008

In the braking of a railroad car, mechanical brake systems using wheel tread and brake disk are applied as well as electrical brake systems by regenerator and rheostat. It is very important to consider the frictional characteristic because kinetic energy of the vehicle is dissipated as converted thermal energy through friction between disk and brake pad during disk braking. A friction coefficient and wear characteristic are decided from the interrelationship of disk and friction material in the disk brake system. Lab-scale dynamometer test on developed brake disk materials for increasing heat resistance was performed in this study. Each candidate material was tested at various braking speeds and pressures and we obtained the friction coefficient and wear characteristic. And we executed comparative evaluation of the result from the test.

• KSTLE International Journal
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• v.7 no.2
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• pp.56-60
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• 2006

By the increasing amount of vehicles, the increase of car accident served as a major momentum for remind the importance of braking system. The adequate design of a passenger car braking system, which is directly related to the safety of a car, is very important since the safety is an essential design parameter of a car to keep men and car from the damage. The thermal behaviors of the ventilated disk has been investigated based on the air cooling effects during repeat braking operations. In this study, the temperature and velocity fields of 3-D unsteady simulated model are obtained using a software package "FLUENT". The numerical results show that there exits a temperature nonuniformity between the disk faces contacting with pads.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.519-524
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• 2004

This study is concerned with the braking distance estimation using frictional energy rate. First, steady state rolling analysis is performed, and using this result, the braking distance is estimated. Dynamic rolling analysis during entire braking time period is impratical, so that this study divides the vehicle velocity by 10km/h to reduce the analysis time. The multiplication of the slip rate and the shear stress provides the frictional energy rate. Using frictional energy rate, total braking distance is estimated, In addition, ABS(Anti-lock Brake System) is considered, and two type of slip ratios are compared, One is 15% slip ratio for the ABS condition, and the other is 100% slip ratio which leads lo the almost same braking distance as the elementary kinematic theory. A slip ratio is controlled by angular velocity in ABAQUS/Explicit, A 15% slip ratio gives the real vehicle's braking distance when the frictional energy occurred al disk pad is included. Disk pad's frictional energy rate is calculated by the theoretical approach.