New Method to Identify Dynamic Normal Stiffness and Damping of Shims for CAE Modeling 2010-01-1711

One of the most important means used for suppressing squeal noise in disc brakes is the application of shims on the pad backplates. In many cases this proves a very efficient tool depending on the type of shim applied in the specific cases. Building up knowledge on the effects of shims have been ongoing for several years, and measuring the important parameters characterizing the shims is crucial for understanding how to develop and implement the shims in an optimal way. Several methods are described in literature for measuring the constrained layer damping effect and one method is described for direct measurement of the shear stiffness and shear damping properties. However, up to now no method has been available that can measure and characterize the normal stiffness and damping properties of shims. This is one of the most important properties of shims as it controls the de-coupling effect in the direction of the normal forces. This has a big influence on system instabilities and noise. In the work described in this paper a new method has been developed and verified, which will be used as basis for a standard for measuring shim dynamic normal stiffness and damping. These data improve the CAE models for stability analyses, which is shown in examples.