The aim of this investigation was to study automotive disc brake cooling characteristics experimentally using a specially developed spin rig and numerically using finite element (FE) and computational fluid dynamics (CFD) methods. All three modes of heat transfer (conduction, convection and radiation) have been analysed along with the design features of the brake assembly and their interfaces. The spin rig proved to be very valuable equipment; experiments enabled the determination of the thermal contact resistance between the disc and wheel carrier. The analyses demonstrated the sensitivity of this mode of heat transfer to clamping pressure. For convective cooling, heat transfer coefficients were measured and very similar results were obtained from spin rig experiments and CFD analyses. The nature of radiative heat dissipation implies substantial e ects at high temperatures. The results indicate substantial change of emissivity throughout the brake application. The influence of brake cooling parameters on the disc temperature has been investigated by FE modelling of a long drag brake application. The thermal power dissipated during the drag brake application has been analysed to reveal the contribution of each mode of heat transfer.

Detailed computational fluid dynamics (CFD) analyses of airflow and convective heat dissipation from a standard disc with radial vanes gave vital information regarding its weak points. Heat transfer from vanes is found to be particularly non-uniform, offering the largest scope for increasing local and average values of the coefficient of convective heat dissipation. A relatively simple modification — installation of an additional small vane (per channel, between the existing vanes) — demonstrated the ability to increase convective cooling from the ventilation channels. The radial position of these additional vanes was altered from disc ID towards OD, and best results were obtained with the vanes placed at the channel outlets (OD). An improvement in the total convective cooling (product of the average convective heat transfer coefficient and the entire disc wetted area) of nearly 14 per cent was achieved. In spite of better cooling, the new design has lower mass (air) flow when compared with the baseline design. The results are also presented in the form of Nusselt numbers, enabling their wider use. Conducted validation provided strong confidence in the accuracy of the results when searching for new solutions.

The nature of the contact and pressure at the interface between thefriction material pad and the disc rotor of a 'spot'-type disc brake affects the performance of a brake in terms of torque, temperature distributions and wear. Interface contact and pressure distributions have been predicted for a particular design of floating caliper passenger car disc brake, using three-dimensional finite element analysis under static and dynamic brake actuation conditions. The influence of friction material compressibility, pad backplate thickness, co&cient of friction, caliper flexure, disc stiflness and actuating piston contact with the piston bore on the interface pressure distribution is examined. The eflect upon brake performance is discussed in terms of 'centre of pressure' and corresponding braking torque, and in terms of observed eflects such as temperature and wear distribution. The results confirm that in order to ensure consistent disc brake pe$ormance the interface pressure distribution should be carefully controlled by designing in mechanical rigidity, compliant friction materials and minimum compliance during brake operation.

Heat generated at the sliding interface between the friction material and the mating surface of a friction brake is not uniformly distributed over the sliding surfaces but depends upon the local interface pressure. Many thermal problems associated with brake friction pairs, including performance variation (fade, speed sensitivity) and rotor damage (heat spotting and thermal cracking) can be analysed in terms of localized frictional heat generation as discussed here. This paper describes how the thermal effects of interface pressure distribution may be divided into bulk temperature effects, such as brake drum expansion and brake disc coning, and its macroscopic thermal effects, such as heat spotting, and suggests how the two are related through the process of thermoelastic instability. The results of analyses, using finite element methods, indicate that uniform friction interface pressure is very important in minimizing brake thermal problems. However, more basic research in the area of interface contact and pressure distribution, and frictional heat generation and dissipation, still remains to be done in order to understand fully the role played by each part of the friction pair in thermally related braking problems.

The main aim of the research is to support the development of the commercial vehicle electric parking brake. Though nowadays widely used on passenger cars, electric parking brake applications on commercial vehicles present completely different challenges. With the brake mass, thermal capacity and required clamp forces an order of magnitude higher, safe parking demands much more attention. In the first instance, the priority is placed upon predicting heat dissipation from the brake disc only. The research is presented in two parts; part one (presented here) focuses on analytical modelling and experimental verification of predicted disc temperatures over long cooling periods, with part two investigating the air flow, velocities and convective heat transfer coefficients using computational fluid dynamics modelling, also followed by experimental validations. To begin the analytical analysis, a study was conducted into the variance in mean local convective heat transfer coefficients over a simplified brake disc friction surface, by investigating typical dimensionless air properties. A nonlinear equation was derived for the average surface convective heat transfer coefficient ([Formula: see text]) variability with temperature drop for the entire cooling phase. Starting from fundamental principles, first-order differential equations were developed to predict the bulk disc temperature. By including variation of the convective and radiative heat dissipation throughout the cooling period, a good correlation was achieved with measured values, to within 10%. Experiments were conducted on a specifically designed thermal rig which uses 15 kW induction heater to heat the disc. Numerous experiments proved the results are very repeatable, throughout the cooling period. It was established, for the grey cast iron brake disc with a fully oxidised surface, the emissivity value are practically constant at ɛ = 0.92. Although the research is being conducted on a brake disc, the results have generic application to any disc geometry, whatever the application.