The Analysis of Brake Squeal Noise Related to the Friction Properties of Brake Friction Materials

The friction properties related to squeal noise was analyzed with the development histories and simplified computational method. Firstly, the development histories were investigated especially focusing on the case which the friction materials were modified to improve squeal noise occurrence. Based on the histories, the friction properties of selected friction materials were newly measured using dynamometer. The average friction coefficient levels, torque oscillations, the increment of friction coefficient during full-stop, and etc. were compared with the squeal noise occurrence, and the results showed that increase of friction properties cause production of squeal noise. The result suggested that the size of friction energy was important factors related to triggering the squeal noise. Also, the contact conditions between rotor disc and friction materials were significant factors deciding the noise occurrence. We performed simplified computational analysis using MATLAB program to prove the effect of friction energy on the noise occurrence. The friction surfaces were roughly designed and the distribution of contact plateaus was controlled to simulate different contact conditions. The different contact conditions were designed and performed sliding at low velocity condition to observe stick-slip phenomena. The friction energy was calculated with the amplitude of stick-slip for each case. The results showed that when the similar sized contact plateaus were increased, friction energy or the amplitude of stick-slip was also increased. And the total size of contact plateaus, which denote contact area, also affected the amplitude of stick-slip profile. Therefore the computational analysis supported the test results. In this study, we suggest that the design of friction surface considering contact condition is important to reduce triggering of the squeal noise.