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The development process of automotive brakes is known to be challenging and time-consuming. It is an iterative process consisting of interplay between brake squeal simulation and extensive experimental investigations of the brake system at the test rig and in the vehicle. In this context, the complex eigenvalue analysis (CEA) of linearized FE models is a part of standard development process of brake systems. Nevertheless this linear analysis has not reached the status of a predictive tool yet, remaining a tool accompanying experimental investigations of the brake system only. Possible reasons may be inadequate simplifications of frictional contact, damping effects and friction material modeling on one hand and insufficiencies of the mathematical mechanical models themselves, i.e. linear vs. nonlinear stability analyses on the other hand. The extensive experimental investigations apply time consuming standard test procedures and need efficiency improvement.

Friction material properties influence brake squeal simulation results decisively. It is well known that friction materials exhibit nonlinear and transversely isotropic characteristics dependent on the type and direction of loading. In order to improve brake squeal prediction reliability, friction material properties identified under squeal loading conditions have to be introduced to the simulation models. Because of this fact, the development of a measurement and identification method for friction material properties in context of brake squeal simulation is in progress. The present paper presents the further developed Dynamic Compression Test Rig (DCTR) and the enhanced evaluation method for the estimation of the normal dynamic component stiffness of friction material specimens under typical squeal conditions. In general, the development of testing procedures implies a set of influence and uncertainty factors, which may influence measurement results decisively.

Brake lining material is one of the main factors influencing brake squeal. Actual simulation of brake squeal suffers on the missing of correct material parameters identified under conditions relevant for squeal. The comparison of different measurement methods for friction material characterization, e.g. compressibility tests, modal analyses or ultrasonic measurements shows that the material properties strongly vary depending on the testing conditions which are static preload, dynamic amplitude, frequency range and the loading direction. The different results obtained from these various test procedures show a nonlinear and transversely isotropic material behavior of the brake lining. In order to identify the correct material parameters for successful brake squeal simulation it is necessary to reproduce the operating conditions during the squealing state as close as possible in experimental setups.