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Evaluating the maximum temperature of ventilated brake discs at bus drop-off points using thermodynamics of friction and wear equations
Alexander Yevtushenko, Peter Gerges
Faculty of Mechanical Engineering, Technical University of Bialystok, 45C Wiejska Street, Bialystok, 15-351, Poland Tel: + 1 - 48-85-7469200.
This paper uses FEM to numerically calculate the transient temperature changes of the brake disc during multiple braking processes. The main purpose of the study is to determine and compare the average temperature, flash temperature and maximum temperature under different convective cooling conditions. The established numerical model of the flying disc takes into account the mutual coupling of the aircraft speed. Temperature, thermal sensitivity of brake element materials, contact pressure and convective heat transfer are all consistent with the assumptions of Thermal Dynamics of Friction and Wear (HDFW). Combining the solution of the initial value problem of the equations of motion with the solution of the boundary value problem of heat conduction, the coupling is obtained.
Keywords: temperature; disc brake; friction coefficient; heat transfer coefficient, finite element method
1 Introduction
An increase in the temperature of the friction elements of the braking system affects the interdependent characteristics of their operation, such as contact pressure, vehicle speed, material properties, friction coefficient, pad and disc wear, and convective and radiative heat transfer [1,2] . Frictional heating is particularly strong under repeated braking cycle conditions with relatively short cooling periods, when the initial temperature of subsequent applications is higher than the corresponding temperature at the beginning of the previous braking cycle. During multiple braking processes, the correct determination of the temperature of the friction surface also becomes difficult due to the long duration of the process and the possible accumulation of errors due to the introduction of simplifications of the calculation model compared to a single short-time braking. more difficult [3].
Electric heaters. After uniformly heating the disk to around 200°C, the temperature drop was measured at different constant angular velocities. To calculate the temperature field within the brake disc, computational fluid dynamics (CFD) methods are used. The wheel assembly was not considered in the analysis. The main goal of the study is to determine the distribution of convective heat transfer coefficients from local flow conditions. The FE braking model with wheel assembly and drag braking conditions was then simulated.
In the literature [4], experimental studies and numerical calculations of heat transfer within the brake disc were carried out to obtain its cooling characteristics. Heat conduction, convection and thermal radiation are considered. Air flow characteristics and temperature were measured on a rotating device using thermocouples and infrared sensors. Different from the normal conditions of braking operation, in this study, the heat source is
Literature [5] used FEM and Taguchi technology to study the influence of brake component design and material factors on braking performance. In the computational model, both convective and radiative heat transfer are taken into account. To evaluate the convective heat transfer coefficient, a Nusselt number representing a rotating disk in a turbulent crossflow is specified. When calculating the Reynolds number, the characteristic length is equal to the radius of the brake disc and the velocity corresponds to the speed of the vehicle. The additional reduction factor allows other vehicle components surrounding the brake assembly to be taken into account. A similar formula, also including a component of the Prandtl number, is used in Reference [6] to determine the heat transfer coefficient. Temperature changes at different locations under the earth's surface and cooling efficiency expressed by α[=(thermal convection)
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