Investigation of high-frequency squeal in a disc brake system using a friction layer-based coupling stiffness

This paper presents a two degree of freedom model for disk brake systems that makes use of the concept of a friction layer-based coupling stiffness. This model is then used to investigate noise and vibration, especially high-frequency squeal. It is shown that for automotive brake systems, the friction layer plays a significant role in the performance characteristics. Hence, the coupling stiffness between the brake pad and the rotor is modelled as a combination of the elastic stiffness of the friction layer superimposed on the coupling modal stiffness of the brake-pad combination. The elastic properties of the friction layer are obtained from nano-indentor tests and the contact area is approximated using light microscopy and scanning electron microscopy analysis. The coupling modal stiffnesses are obtained from impact tests and finite element studies. Preliminary results from the model are consistent with the actual high squeal data collected from the field. The main objective of this work is to introduce a new way of modelling the coupling stiffness based on the properties of the friction layer, which has not been extensively studied till now.