Abstract
KEYWORDS – brake squeal, complex eigenvalue analysis, pad abutment, bench test, contact linearization
ABSTRACT
The principal mechanics of a car brake system has not changed since more than 100 years, but brake noise vibration issues still remain challenging not only for the car manufactures and their suppliers, but also for the basic researchers at universities. In order to predict noise and vibration behavior of the brake system and furthermore design and evaluate countermeasures, simulation tools have been extensively applied. Despite its well-known disadvantages, the so called ‘Complex Eigenvalue Analysis’ (CEA) is the preferred tool for industry applications, because its fast calculation time and it’s easy to apply.
For the CEA a linearization of the system equations is necessary. However, it is well-known, that there are large nonlinearities in the brake system, e.g. the contacts. The pad / disc contacts are the subject of many researches, but the contact between pad abutment and caliper is often neglected. Thus for many driving maneuvers these contacts can be very important to describe more realistic results.
This paper first points out in a realistic brake example, why the abutment contacts are important. Afterwards, a research bench setup is presented which allows measuring the modal behavior of the brake pad in a fixed caliper brake. The acceleration of the pad and the caliper is measured. The results of the bench tests are then compared to the simulated modes of different states of the linearized brake system. It is found, that the contact states at the abutment are influencing the system modes and thereby the instability behavior of the brake system. With a simplified brake model, new approaches to model the linearized pad abutment contacts are discussed, which can be included in standard robustness analysis.
To summarize, a new simulation approach is presented, which can improve the standard CEA models and enables to simulate additional load cases of the brake system helping to generate more realistic results