Brake squeal significantly reduces comfort in passenger vehicles and is still a frequently objected noise in the development of disc brakes. The mode coupling effect is held to be responsible for the brake squeal emission. The frequencies of two adjacent eigenmodes approach and coalesce with an increasing friction coefficient between the brake disc and the brake linings. Complex eigenvalue analysis (CEA) is widely used to determine mode couplings by calculating the complex eigenvalues. The real part of these eigenvalues is a measure for unstable oscillations corresponding with the propensity to brake squeal. In the last decades, researchers have attempted to reduce the brake squeal propensity by shifting the mode coupling towards higher friction coefficients, e. g. by increasing the distance of the frequencies of 'coupling-critical' eigenmodes by structural modifications. However, these structural modifications may change other frequencies, lower their distance and result in a mode coupling at another frequency. This work presents an approach to shifting mainly one frequency of a specific eigenmode by topology optimization while fixing other eigenfrequencies to their original values. The approach is applied first on a single component and then on a brake assembly to avoid one specific mode coupling. The results show the method's potential and its limitations in influencing only one frequency for a given structure. In the end, our studies expose that only increasing the distance of adjacent frequencies may not compulsorily avoid mode coupling.
Ing. Marcel Deutzer, Calculation Engineer in virtual brake development, Volkswagen AG; Prof. Dr. Norbert Hoffmann, Professor, Hamburg University of Technology Dynamics Group