Animations of a disc brake generating noise

Previous work on generating animations from real disc brake systems generating noise (squeal) has been consolidated and developed. Using the method of double pulsed laser interferometry a series of holograms (typically ten per half cycle) can be recorded from the brake during a cycle of excitation. From these holograms a considerable amount of data can be obtained about the vibration of the disc and pad surfaces. Standard methods from image processing and algorithms developed to investigate hologram fringe lines can be used to generate three-dimensional representations of the surfaces. Furthermore although part of the disc surface and even more of the pad surface are obscured by the calliper, etc., it has been possible to form a reliable numerical reconstruction of the whole disc and pad surfaces partly by using standard mathematical approximation techniques and partly by intelligent extrapolation of the available data. From these an extension of previous animations to show the full disc and pad surfaces undergoing vibration can be obtained. Using a Fourier analysis of the numerical data indicates a possible way to construct reliable mathematical models of real disc brake systems.