(Dr. Kenneth Cunefare, advisor)

"Modal Analysis of a Squealing Disc Brake via Sound Intensity and Laser Doppler Vibrometry"

Abstract

Disc brake squeal has been determined to be audible vibrations above 1 kilohertz that occur occasionally during vehicle breaking; furthermore, squeal has been shown to be influenced heavily by, but not necessarily equal to, the natural frequencies of the brake rotor or disc.  Brake squeal is thought to be caused by self-excited vibrations of the brake assembly as a result of stick-slip phenomena occurring between the pads and the rotor.  Past experimental  and analytical methods that have been used to analyze the mode shapes of the rotor include holographic inteferometry and finite element analysis.

The purpose of this research is to determine experimentally the mode shapes for a disc brake under squeal conditions using both sound intensity and Laser Doppler Vibrometry.  An advantage of sound intensity is that, being a vector quantity, it can be measured in the presence of steady external noise sources, while a benefit of Laser Doppler Vibrometry is that it allows non-contact vibration measurement of the test article.  These tow methods will provide the means to visualize the mode shapes of the squealing disc through computer analysis and through near-field sound intensity levels; moreover, the results using these two methods should be similar since prior research has demonstrated a relationship between mode antinodes and larger sound intensity levels.