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The complex eigenvalue analysis has been used by the brake research community to study friction-induced squeal in automotive disk brake assemblies. The analysis process uses a nonlinear static pre-stressed normal modes analysis simulation sequence followed by a complex eigenvalue extraction algorithm to determine the dynamic instabilities. When brake hardware exists, good correlation between analysis results and experimental data can be obtained. Consequently, complex eigenvalue analysis can be a valuable method in an effort to understand brake components that might have a propensity to influence the noise behavior of a brake system. However, when hardware does not exist and the complex eigenvalue method is asked to be predictive, it becomes a difficult, if not impossible task. This paper will focus on some of the reasons the complex eigenvalue analysis method is not a reliable predictor of friction-induced squeal in automotive disk brake assemblies.

A front disc brake system is used as an example for an investigation of low frequency squeal. Many different modifications to this disc brake system have been proposed and this paper focuses on a solution that reduces the stiffness of the rotor. This is accomplished by a reduction in the Young's modulus of the rotor material. The complex eigenvalue method is used for a detailed analytical study in order to obtain a better understanding of this solution technique. Modal participation factors are calculated to examine the modal coupling mechanism. Parametric studies are also performed to find out the effects of friction coefficient and rotor stiffness. Results show that shifting rotor resonance frequencies may ecouple the modal interaction and eliminate dynamic instability, which is in agreement with experimental results.

This paper documents the advantages of brake corner system modeling and simulation over traditional component analysis techniques. A better understanding of the mechanical dynamics of the disc-braking event has been gained through brake corner system modeling and simulation. Single component analyses do not consider the load transfer between components during the braking event. Brake corner system analysis clearly quantifies the internal load path and load transfer sequence between components due to clearances or tolerance variations in the brake assembly. By modeling the complete brake corner assembly, the interaction between components due to the contact friction loads and variational boundary conditions can be determined. The end result permits optimal design of brake corner systems having less deflection, lower stress, optimum material mass, and reduced lead-time for new designs.