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Please use this identifier to cite or link to this item: https://dspace.lboro.ac.uk/2134/23868

Title: Frictionally induced, self excited vibrations in a disc brake system
Authors: North, M.R.
Issue Date: 1972
Publisher: © M.R. North
Abstract: This work describes an investigation into the frictionally induced, self excited vibrations which occur in braking systems and are generally known as squeal. The.work is largely theoretical, but measurements made on a rig are used to correlate the predictions of the theory with a practical brake system. Following an historical review, the theoretical behaviour of a brake disc is examined and adapted to predict the approximate natural frequencies and nodal spacings of an annular disc for a range of masses added to the disc to represent the pads and caliper. Knowing the disc behaviour, it is then possible to propose an eight degree of freedom model which describes the caliper, pads and a lumped model of the disc in the immediate vicinity of the caliper. From this model it can be shown how self excited vibrations can arise in such a system, and squeal frequencies and mode shapes can be predicted. The effects of stiffness non-linearity in the system are then investigated and it is shown that limit cycles will occur; conditions for obtaining mode shapes at the limit cycle are defined. An experimental rig is described and measurements made on the rig are given in some detail. Parameter values are inserted in the mathematical models and mode shapes and natural frequencies are computed. These are compared with the measured mode shapes and natural frequencies to give an assessment of correlation between the theory and the actual vibrational behaviour. Despite the simple nature of the model used to represent the brake system, and the fact that a number of parameters are only known within wide limits,.correlation between the measured mode shape and squeal frequency and the calculated mode shapes and frequencies can be made good by the choice of suitable parameter values within the defined limits. For example, a 26% reduction in the caliper stiffness altered the mode of the disc vibration and hence caused a large change in squeal frequency, but insertion of the new parameter values into the equations showed that a corresponding instability was predicted at the correct frequency.
Description: A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.
URI: https://dspace.lboro.ac.uk/2134/23868
Appears in Collections:PhD Theses (Aeronautical and Automotive Engineering)

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