The paper deals with the study of a possible dissipation induced instability in a disc brake system, which leads to a self-excited vibration and thus to a brake squeal. The work describes an experimental estimation of the damping properties of a disc component of the simplified disc brake system. The stability of the system is analyzed numerically using the Finite Element approach and the Complex eigenvalue analysis. From the evolution of real parts of the eigenvalues with friction, the friction threshold value destabilizing the system is defined for the undamped and non-proportionally damped system. From the results, it can be seen how the damping non-proportionality can lead to the dissipation-induced instability of the disc brake system.
Abstract:Paper describes the mechanism of vibration of a minimal automotive disc brake model which can lead to unwanted effects known as brake Noise Vibrations and Harshness (NVH). Stick-slip frictional effects are mathematically described by simplification of physical assumptions. Self-excited vibrations due to stick-slip and also stability conditions are defined using a 1 degree of freedom mechanical system. Non-Coulomb nonlinear behavior of the friction force with negative slope is considered. Response is obtained by the numerical solution of ordinary differential equation.
The evaluation of disk brake squeal is nowadays performed using Finite Element Model. In this standard procedure the thermal effects are omitted. The omission is done because of long computing time of fully coupled brake system thermo-structural transient analysis. This paper is presenting an effective uncoupled thermo-structural FEM procedure. This method is applied on a pin-on-disc system and its time effectiveness is compared to standard full coupled transient analysis.
The paper describes role of non-proportional damping in flutter type instability, demonstrated on simplified disc brake model. The discrete two degrees of freedom system is considered to imply damping induced instability through a system eigenvalues evaluation. The Frequency Response Function (FRF) is further calculated from measurements on the physical disc brake model. From FRF, damping properties are estimated and discussed. Several different loading states of the pad versus disc are considered to show loading impact on FRF and thus damping of the system.
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