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Thermo-elastic and thermo-plastic behaviour takes place with a disc brake during heavy braking and it is this aspect of braking that this paper considers. The work is concerned with working towards developing design advice that provides uniform heating of the disc, and equally important, even dissipation of heat from the disc blade. The material presented emanates from a combination of modeling, on-vehicle testing but mainly laboratory observations and subsequent investigations. The experimental work makes use of a purpose built high speed brake dynamometer which incorporates the full vehicle suspension for controlled simulation of the brake and vehicle operating conditions. Advanced instrumentation allows dynamic measurement of brake pressure fluctuations, disc surface temperature and discrete vibration measurements.

This paper is concerned with addressing the problems experienced with the thermo-elastic behaviour of the disc - that of optimum heat dissipation, and equally important, even heating of the disc blade. The primary objective is to develop a more temperature-stable brake disc. The work presented approaches the problems of thermal judder through benchmarking the current situation. This is approached by modelling the current brake and its validation by means of vehicle and laboratory testing. The empirical work is centred on a bespoke high speed brake dynamometer which incorporates the full vehicle suspension for an accurate yet controlled simulation of brake and vehicle operating conditions. The dynamometer is housed in a purpose built laboratory with both CCTV and direct visual access. It is capable of dynamic measurement of DTV, caliper pressure fluctuations, disc surface temperature and vibration measurements at discrete points about the rig.

Laser holographic methods have been successfully used to produce animations showing the out-of-plane vibrations that take place in both the disc and pad of a real brake system generating noise (squeal). A series of holograms made at different times in the cycle of vibration were used to give the data on which the animations were based. Further it has been shown that mathematical approximations made to the fringe patterns obtained in the holograms by this method give phase and amplitude information about the wave motion involved. It establishes the existence of travelling waves on the brake disc with a speed given by the angular frequency of the noise divided by the mode order. This approach has now been extended to examine a time-related series of holograms of the disc rim of a brake system. From the data obtained from these holograms it has been possible to develop animations that show the in-plane vibration in the disc of a brake system producing noise.

Brake noise investigations using the whole body visual technique of double pulsed holographic interferometry have been extended so that a series of interferograms may be recorded over a cycle of excitation providing information about the amplitude, direction, phase relationship and the mode of vibration of the principal component parts of the brake. This work investigates the possibility of automatically interrogating the holographic images and creating an animated 3 dimensional image of a brake generating noise.