The onset of squeal vibrations in drum brake systems resulting from a coupled mode instability

Brian Kent Servis, Purdue University

Abstract

In the last two decades there has been a great deal of research done to model, predict and understand brake squeal in both disc and drum brakes. The goal of this study was to build a sufficiently accurate analytical model that can be used to predict brake squeal and to gain a better understanding of some of the mechanisms responsible for squeal. Using trial functions based on approximate as well as derived exact uncoupled natural frequencies and mode shapes a set of equations of motion was derived. These equations of motion account for as many aspects of the model as is appropriate to accurately represent the system. From the complete model a simplified model was extracted. The simplified model was used to gain a fundamental understanding of the brake system and its response to parameter changes. The complete model was validated against experimentally measured responses. From the model it can be deduced that as the coupling in the system is increased the system may become unstable. The instability is the result of merging system modes that allow for a self excited vibration to occur. A method to observe the modal contribution of the uncoupled modes at the onset of squeal and prior to squeal is introduced. An understanding of why certain fundamental modes contribute more than others can be used to modify system or predict if a system will squeal.

Degree

Ph.D.

Advisors

Krousgrill, Purdue University.

Subject Area

Mechanical engineering

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