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Finite element simulations are widely used for simulating disc brake squeal and the aim of this paper is to further increase the understanding of the effect of insulators. An earlier paper has presented an experimental technique for measuring the properties of the viscoelastic materials [1] and it has been shown how these data can be used in simulating brake response [2]. This paper deals with the sensitivity of a FE brake model to frequency dependent shim material properties and it is documented that with the current options for modeling shims in complex eigenvalue analysis it is only possible to accurately simulate response in a narrow frequency range. A procedure to find optimized parameters for a current damping model is discussed. The best α and β values for a Rayleigh damping model is found by obtaining a least square best fit in a frequency range of interest.

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.

A mathematical model for representing the vibration behavior of a disc brake is presented. Special emphasis has been put on the need to simulate the high frequency response by the use of continuous flexible elements, to represent the most important components of the brake. The simple mathematical modeling approach allows for conceptual understanding of the squeal generation mechanisms. In this study, the effect of the variation of system parameters over the length of the components, is investigated.

Disc brake squeal is a widespread cause for discomfort. The purpose of the work is to gain insight into the disc brake squeal problem and to investigate the mechanisms that generate instabilities that leads to audible noise. This paper presents a mathematical model for high frequency disc brake noise. Information of the flexible properties of the components is used to generate a small yet appropriate model. By using the technique of “Assumed Modes Method”, a model incorporating the flexible properties of a continuous disc can be accomplished resulting in only a limited number of degrees of freedom. Knowledge of the modal properties of disc and pads are used to select assumed modes for the model components. The basic concept of mode coupling is the starting point: Two orthogonal modes are present in a disc at the same frequency owing to it's rotational symmetry.