• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.817-822
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• 2017

The braking system is one of the most important components in vehicles and machines. It must exert a reliable braking force when they are brought to a halt. Generally, frictional heat is generated by converting kinetic energy into heat energy through friction. As the kinetic energy is converted into heat energy, high temperature heat is generated which affects the mechanical behavior of the braking system. Frictional heat affects the thermal expansion and friction coefficient of the brake system. If the temperature is not controlled, the brake performance will be decreased. Therefore, it is important to predict and control the heat generation of the brake. Various numerical analysis studies have been carried out to predict the frictional heat, but they assumed the existence of boundary conditions in the numerical analysis to simulate the frictional heat, because the simulation of frictional heat is difficult and time consuming. The results were based on the assumption that the frictional heat is different from the actual temperature distribution in a rotating brake system. Therefore, the reliability of the cooling effect or thermal stress using the results of these studies is insufficient. In order to overcome these limitations and establish a simulation procedure to predict the frictional heat, this study directly simulates the frictional heat generation by using a thermal-structure coupling element. In this study, we analyzed the thermo-mechanical behavior of a brake model, in order to investigate the thermal characteristics of brake systems by using the Finite Element method (FEM). This study suggests the necessity to directly simulate the frictional heating and it is hoped that it can provide the necessary information for simulations.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.6
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• pp.95-103
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• 2006

Wheel treads of E.M.U. are usually under a heavy thermal load by brake frictional heat between wheel and brake shoe and damaged by repeated thermal and mechanical loads. To examine the cause of wheel tread damage of E.M.U.'s in service running, a systematic approach has been used. This study is composed of three parts. Frictional heat analysis was conducted in the first part by finite element method. Two kinds of brake shoes in service were considered. In the second part, experimental study was carried out on a brake dynamometer. Temperatures were measured for the two brake shoes. And experimental study in service running E.M.U.'s was performed. Wheel and brake shoe temperatures were measured by using thermocouples and temperature indicating strips. Finally metallurgical characteristics were examined by a SEM/EDS and the cause of the wheel damage was analyzed. It seems that aggregated ferrous component is a main cause of the wheel tread damage.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.88-93
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• 2005

Frictional heat generates when the brake shoes are in contact with wheel tread under high pressure for EMU's speed control, stopping, and deceleration. Such a frictional heat has a significant effect on the wheel tread. In order to analyze the characteristics of frictional heat and measure the amount of the generated heat, tests by using a brake dynamometer and for running vehicles are carried out. In addition, finite element analysis is performed to simulate the temperature distribution and thermal analysis of the brake shoes. Through the tests and the simulations, it is found that the problems by temperature increase at tread braking are verified.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.8
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• pp.65-71
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• 2008

This paper presents a transient heat transfer analysis of a drum brake shape. The transient heat transfer analysis of automotive drum brakes with frictional contact is performed by using the finite element method. The drum brake type studied in the page is the internally expanding one in which two shoes fitted externally with frictional material are forced outward against surface a rotating drum on the wheel unit. In this case, the braking power is produced by the friction force between a drum and a lining, and is converted into heat. The brake drum has constant material properties. The air inside the drum has temperature-dependent thermal conductivity and enthalpy. Radiation effects are ignored. The result explains the reason why hair crack and cause of drum failure occur. The temperature of drum is in proportion to the drum thickness and nonlinear changes at every points of drum. It's necessary for the decrease of the drum temperature to make the air inside drum flow.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.4
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• pp.563-569
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• 2008

During braking operation, the surfaces of disk have severe contact conditions and high frictional heat would be generated between disk and pad surfaces. The heat makes high temperature gradient on disk surfaces and results in thermal deformation. To enhance the frictional heat dissipation, heat pipes are embedded in the ventilated type disk along the radial direction. The temperatures of the inner vent type disk and the brake disk with heat pipes are compared at the same operating conditions. By comparison a brake disk with heat pipes has higher cooling performance than the inner vent type disk.

• Tribology and Lubricants
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• v.26 no.1
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• pp.31-36
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• 2010

The brake system is an important part of the automobile safety system. The disc brake system is divided into two parts: a rotating axi-symmetrical disc, and the stationary pads. The frictional heat, which is generated on the interface of the disc and pads, can cause high temperatures during the braking process. The frictional heat source (the pads) is moving on the disc and the location is time-dependent. Our study applies a moving heat source, which is defined by the time and space variable on the frictional surface, in order to simulate the frictional heat behavior accurately during the braking process. The object of the present work is the determination of the temperature distribution and thermal stress in the solid disc by non-axisymmetric 3D modeling for repeated braking.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.842-846
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• 2005

A brake disk and a pad are important parts that affect the braking stability of a railway vehicle. Especially, because a brake disk stops the vehicle using conversion of the kinetic energy to frictional energy, thermal fatigue cracks are generated by the cyclic thermal load, as frictional heat, on a frictional surface and these cracks cause the fracture of a brake disk. Therefore, many researches for the thermal stress must be performed to improve the efficiency of brake disk and ensure the braking stability. In this study, we performed the thermal stress analysis for a ventilated brake disk with 3-D analysis model. For that, we simplified the shape of a ventilated hole to minimize problems that could be occurred in analysis process. Thermal stress analysis was performed in case that pressure distributions on a frictional surface is constant and is not. To determine pressure distributions of irregular case, pressure distribution analysis for a frictional surface was carried out. Finally using the results that were obtained through pressure distribution analysis, we carried out thermal stress analysis of each case and investigated the results of thermal stress analysis.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.1
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• pp.67-76
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• 1998

Friction materials for brake linings and clutches have severe performance requirements. The principal function of such frictional elements is to convert kinetic energy to heat, and then either to absorb or to dissipate heat. In order to achieve these objectives, the coefficient of friction must be as high as possible, independent of variations in operating conditions, and the necessary energy conversion must be accomplished with a minimum of wear on the contacting parts. In this study, Al powder, Al bronze powder and Mo powder used in general for automobile brake was sprayed on automobile brake disc to restrain rust and to maintain friction performance. Dynamo and corrosion tests have been carried out. It is concluded that the sprayed disc with Al bronze powder has the most improved frictional performance and anti-corrosive characteristics. The main results obtained can be summarized as follows; 1. From the corrosion current density test for gray cast iron and sprayed disc with powders of Al, Al bronze and Mo, it was cleared that the spray treatment with Al bronze powder showed the most superior anti-corrosive characteristics than other powders. 2. By anode polarization toward the noble direction from corrosion potential, corrosion current density with sprayed brake disc by Al-bronze powder was the lowest. 3. Mean frictional coefficients obtained from dynamo test are as follows : the sprayed disc with Al(99.99%) powder was 0.190 ; the sprayed disc with Al-bronze powder was 0.312 ; the sprayed disc with Mo powder was 0.257 ; the non-sprayed disc of gray cast iron was 0.331. In the case of the sprayed disc Al-bronze powder showed the most excellent frictional characteristics . 4. Amount of burnish quantity obtained from burnish test by dynamometer is as follows : the sprayed disc with Al-powder was 1.079 mm : the sprayed disc with Al-bronze powder was 0.155 mm : the sprayed disc with Mo powder was 0.253 mm : the non-sprayed disc of gray cast iron was 0.241 mm. Al-bronze powder also showed the most excellent burnish characteristics.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.93-100
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• 2003

This paper describes the thermoelastic instability arising from friction heat generation in braking and proposes the finite element methods to predict the variation of temperature and thermal deformation. In a conventional disc brake analysis, heat generation is only related with wheel speed and friction material and the interface pressure between disc and pad is assumed constant. But under dynamic braking conditions, the frictional heat causes the thermoelastic distortion that leads to more concentrated contact pressure distribution and hence more and more non-uniform temperature. In this paper, to complete the solution of the thermomechanically coupled problem, the linear relation model between pressure and temperature is proposed and demonstrated in examples of a simple two dimensional contact problem. And the two dimensional model has been extended to an annular three dimensional disc model in order to consider more realistic geometry and to provide a more accurate critical speed for automotive brake systems.

• Tribology and Lubricants
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• v.25 no.6
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• pp.421-426
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• 2009

The brake system is important part of automobile safety system. The disc brake system is divided two parts: the rotating axisymmetrical disc and the stationary pads. During braking, the kinetic energy and potential energy of moving vehicle were converted into the thermal energy through frictional heat between the brake disc and the pads. The frictional heat, which is generated on the interface of the disc and pads, can cause high temperature during the braking process. The object of present work is to determine temperature and thermal stress, to compare to simulation results and experimental results in the disc by partial 3D model of ventilated disc brake with appropriate boundary conditions. In the simulation process, the mechanical loads were applied to the thermo-mechanical coupling analysis in order to simulate the process of heat produced by friction.