Brake-squeal simulation: An efficient approach to define countermeasures

Brake-squeal causes major warranty costs for the automotive industry. In recent years, simulation techniques based on the Finite Element Method approach have become more and more a state of the art technique to predict brake-squeal. However the definition of countermeasures against brake-squeal is mainly based on trial-and-error methods. This work presents a method to identify the sensitivities of the system's behavior with respect to geometrical changes and provides an efficient approach for the definition of countermeasures. Brake-squeal is based on the loss of stability of the brake-system. The system is discretized using the Finite Element Method and stability is evaluated by applying Lyapunov's stability criteria on the system matrices. Due to frictional contact, gyroscopic, circulatory and negative damping terms arise which may cause instability of the system in the mid frequency range. Direct sensitivity and optimization approaches are only less efficient ways to establish system stability due to the large number of degrees of freedom and the computation time. A model reduction based on an orthogonal projection significantly reduces the number of equations and offers the possibility to evaluate system sensitivities as well as excitation mechanisms. Visualization of the excitation mechanism for a specific instable brake-system helps to understand the system's behavior. The computed sensitivities also enable a time and weight efficient way to define countermeasures against brake squeal. This model reduction approach has been applied to Finite Element Method models in current development work. Countermeasures to improve the noise behavior based on this method have been confirmed on testing benches and in car tests.