The last decades have shown extensive efforts on the investigation of automotive disk brake squeal. The origin of brake squeal is seen in self-excited vibrations, caused by the friction forces transferring energy from the rotating disk into the brake system. Based on a very simple model, Popp et al. described in 2002 the conditions for positive work of the friction forces (i.e. excitation of squeal), which depends on the phase shift between the in-plane motion (with respect to the disk) of the brake pad and the friction forces. Experiments on active manipulation of this phase shift using pads with integrated piezoceramic actuators, performed by von Wagner et al. in 2004, resulted in successful suppression of disk brake squeal.
The authors of the present paper used a variety of models for the investigation of the origin of the excitation mechanism by observing phase relations between the friction forces and the vibrations of the pads. Several measurement techniques based on these theoretical investigations are developed in order to detect parameter regions (e.g. brake pressure, temperature, rotation speed) which are suspected to cause squeal. Compared with the state-of-the-art testing of brakes, this procedure provides a very rapid and efficient analysis of the noise behavior and has been verified by experimental results. It also provides a method of testing and modeling the efficiency of standard industrial counter measures to squeal.
