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Brake squeal is caused by dynamic instability, which is influenced by its dynamic unstable structure and small disturbance of friction force variation. Recently, FE Analysis of brake squeal is applied for brake design refinements, which is based on dynamic instability theory. As same as the refinement of brake structure is required for brake squeal reduction, the refinement of pad materials is also required for brake effectiveness and brake squeal reduction. It is well known that friction film, which is composed of polymers like phenol formaldehyde resin and so on, influences for friction coefficient. Therefore it is expected that the refinement of polymers in pad materials enable higher brake effectiveness and less brake squeal. In this paper, Molecular Dynamics is applied for the friction force variation of polymers in pad materials. The MD simulation results suggest the reduction method of friction force variation of polymers.

In order to determine the mechanism of brake squeal generation, six natural squeal odes were identified and the vibrations of the rotor, backplate and lining were measured for each mode by means of accelerometers. The results show that an important factor is the phase difference between the change in friction surface displacement and the change in lining thickness. In the two high frequency modes, it was confirmed that the exciting energy is generated by fluctuations in friction force due to fluctuations in surface pressure. And it was concluded that squeal generation is dependent on the ratio of change in frictional force rather than in the μ-v characteristics.