Abstract
The problem of disc brakes generating noise (squeal) is a serious concern in the automotive industry, but one which is notoriously difficult to predict and eradicate. Research into this problem has been carried out by studying real disc brake systems generating noise, using the technique of double pulsed laser holography.
Considerable knowledge of the mode of vibration of the disc, pads and other components has been obtained by recording three orthogonal high resolution images of the system. The technique has been developed further by using electronic triggering devices which enable a series of time related images to be obtained, corresponding to different times in the cycle of vibration of the braking system.
By digitising the holographic images it has been possible to develop three dimensional graphical representations of the vibrating disc and finger pad surfaces. Furthermore a series of time related images can be used to develop a three dimensional animation of the real disc and pad system generating noise. This graphical representation avoids the need for specialist interpretation of the holographic images.
Using least-squares mathematical approximations it is also possible to generate an accurate Fourier Series type representation of the vibrating disc and pad surfaces which it is believed will be important in developing mathematical models of disc brake.