Analysis of Brake Squeal Noise using FEM Part I: Determination of Contact Stiffness between Rotor and Pads

Brake squeal is a problem that has been faced by several methods in the last decade. Among then, finite element analysis is proving to be a useful tool to predict the noise occurrence of a particular brake system during the design stage. The Finite Element Method (FEM) has been employed to detect unstable frequencies using a complex eigenvalue analysis. These unstable frequencies are related, in most cases, with high sound pressure levels generated during the brake system operation and its detection is an important step in order to produce quiet brake systems. Although the method is fast and provides guidance for solving engineering problems, it is very sensitive to input parameters like material properties and boundary conditions. For brake system modeling, the determination of the contact stiffness between rotor and pads is a crucial point, since one of the major contributing mechanisms to generate squealing frequencies is the modal coupling between these two components. The scope of this paper is to evaluate different methods to obtain the contact stiffness on the rotor-pad interface. Static and dynamic based methods are tested and the results obtained are experimentally validated by a power flow analysis. Moreover, a procedure to estimate the effect of braking pressure on the contact stiffness is showed.