This article is concerned with frictional heating phenomenon playing a central role in disc brake (clutch) systems performance. It was of great interest to carry the description of existing numerical solutions of the problem. The level of the calculations was categorized into three problems. The first is a common approach, drawn primarily on the assumption that the heat flow rate generated at the disc/pad interface is a known quantity. Heat generation was substituted by the intensity of heat flux depending on contact pressure, coefficient of friction and evolution of angular velocity, and radius of the disc product. A more complex description of the braking action was given by the assumption of mutual relation between mating parts of the disc brake system. In this case, the thermoelasticity theory was applied to the model. The facts of existing critical speed is established, in which hot spots caused mainly by contact pressure variations frictionally-excited thermoelastic instability phenomenon entered co...

The FEM-Modeling of the Frictional Heating Phenomenon in the Pad/Disc Tribosystem (A Review)

In this work, 2 vol% carbon nanotubes (CNTs) reinforced aluminum (Al) matrix composites of superior microstructural homogeneity are successfully synthesized using Bc equal-channel angular extrusion (ECAP) route. The key step in arriving at high level of homogeneous distribution of CNTs within Al was preparation of the powder using simultaneous attrition milling and ultra-sonication processes. Microstructure as revealed by electron microscopy and absence of Vickers hardness gradients across the material demonstrate that the material reached the homogeneous state in terms of CNT distribution, porosity distribution, and grain structure after eight ECAP passes. To facilitate comparison of microstructure and hardness, samples of Al were processed under the same ECAP conditions. Significantly, the composite containing only 2 vol% exhibits 20% increase in hardness relative to the Al samples.

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Microstructure and mechanical properties of carbon nanotubes reinforced aluminum matrix composites synthesized via equal-channel angular pressing

Disc brake system is one of the most critical components in a vehicle, which is always exposed to nonlinear transient thermoelastic conditions. Optimal design of a brake system to suit the heat transfer, weight and packing requirements is an ongoing challenge. Substantial researches have been carried out and are underway, in order to address the diverse issues related to thermal, mechanical and structural performances of automobile disc brakes. With the extensive application of numerical tools and techniques, the analyses involved became easier and effective. The present article provides an exhaustive review of the numerical and experimental studies reported so far, on the analysis and design of solid and ventilated disc brakes. The directions for future works are also described. The review reveals that, there is enough scope for extended research for realizing optimal design of disc brake system by truly emulating all the relevant practical situations.

Thermo-Mechanical and Structural Performances of Automobile Disc Brakes: A Review of Numerical and Experimental Studies

In the process of developing the brake disc, it is necessary that we predict the suitability of the design. In this manner, we can affirm that even the first prototype will satisfy all of the customer homologation requests. Usually those comprise different sequential braking tests in which the maximal achieved temperature is the criterion that governs brake disc suitability. The knowledge of how to predict the behavior of a brake disc in the early pretesting phase has a significant impact on development costs and time. The common method that is used for predicting the temperatures in the brake disc during braking is numerical simulation analysis. With the help of Computational Fluid Dynamics, the flow through a vehicle ventilated brake disc of known geometry was determined, and the wall heat transfer coefficients for all vehicle speeds and brake disc temperatures were calculated. The results were then imported into a thermal numerical simulation of a sequential-braking vehicle test. The results showed that the consideration of cooling factors has a significant impact on temperature courses. To obtain accurate results from the numerical simulation and to simulate the vehicle test precisely, the proper wall heat transfer coefficients must be considered. The proposed method produces more accurate numerical results and enables the development engineer to develop suitable brake disc geometry in the early pretesting phase.

Prediction of the cooling factors of a vehicle brake disc and its influence on the results of a thermal numerical simulation

The primary purpose of this basic research is to investigate the structural and mechanical behavior of a three-dimensional disc-pad model during the braking process under dry contacts slipping conditions. A predictive analysis is performed in order to determine the global deformations, Von Mises stress on the disc, and contact pressures on the inner and outer pad at different time of simulation. We first proceed to view the meshed models and predicting variations of tensile or compressive stress normal to the plane and shear stress in rotating disc and ring bodies. In addition, we discussed the sensitivity of some parameters involved in the results of mechanical calculation, such as rotation of the disc, the smoothness of the mesh, the material of the brake pads and the friction coefficient that enters the disc and the pads, the number of revolutions and the material of the disc, and the pad groove.

Three-dimensional finite element modeling and analysis of the mechanical behavior of dry contact slipping between the disc and the brake pads

Elevated temperature low cycle fatigue of grey cast iron used for automotive brake discs

Thermal and stress analysis of disc brakes under specific loads (driving downhill and braking to a standstill) was calculated. The FEM (Finite Element Method) was used to carry out the analysis. The analysis dealt with centrifugal load for two cases of braking, braking to a standstill on a flat surface and braking downhill, maintaining constant speed and afterwards braking to a standstill. The main boundary condition in both cases was the entered heat flux on the braking surface of the disc and the force of the brake clamps. Two different discs were used, one brand new (unused) and one with permitted wearing.

Modelling and Analysis of Thermal and Stress Loads in Train Disc Brakes - Braking from 250 km/h to Standstill

A certain number of railway brake discs made of gray cast iron, showed the presence of small cracks only after a few thousand kilometers. To investigate main causes of a brake disc failure, numerical analysis was done by using ABAQUS software. Numerical analysis resulted from a physical model of heat flux in dependence of braking time. Physical model was applied considering all demands and presumptions given by industry representatives.

Numerical analysis of railway brake disc

A squealing noise of 50 dB was measured on a vehicle homologation test at around 900 Hz on the existing brake drum design, mounted on the rear axle of the mid-sized passenger automobile. Therefore, analysis of eigenfrequencies of the original drum design was performed using the impact hammer test and numerical analysis. It was established that a critical mode shape 0/2 exists at around 900 Hz, exactly where the squeal noise was recorded at the brake road noise evaluation vehicle test. The analysis was carried out with the intention to eliminate the possibility of the squealing noise by increasing the critical mode above 900 Hz. The relation between different brake drum modifications parameters and the eigenfrequencies was determined and the best solution was obtained. The first eigenfrequency of the proposed drum design was increased by 58 Hz and the difference between the in-plane and out-of plane mode shape was sufficient. We can conclude that the modified drum design will not have squeal issues at 900 Hz as there are no eigenfrequencies of the brake drum in that range and therefore the problem of the loud brake is solved.

Modifying the brake drum geometry to avoid selfexcited vibrations and noise

This paper shows the thermal and stress analysis of the worn brake disc for a Taurus class locomotive. The numerical analyses are carried out under the experimental testing program, Prufprogramm No. 5, which is adjusted for this type of locomotives by UIC CODE 541-3. The simulations results under mentioned program show the most unfavorable case of braking. The numerical analysis is done with the finite element method (FEM), using ABAQUS software.

Grega Oder

Papers

Elevated temperature low cycle fatigue of grey cast iron used for automotive brake discs

Modelling and Analysis of Thermal and Stress Loads in Train Disc Brakes - Braking from 250 km/h to Standstill

Numerical analysis of railway brake disc

Modifying the brake drum geometry to avoid selfexcited vibrations and noise

Numerical analysis of braking discs for a Taurus class locomotive