Analysis of Disk Brake Squeal Using Substructure Synthesis Method 2003-32-0042
This paper describes a numerical analysis method for predicting the brake squeal using the Substructure Synthesis Method. This method is more accurate than the classical method based on the mass-spring system, and simpler than the analysis of all the brake system by FEM. The squeal studied here is focused the one occurring in the low frequency range and its mechanism is due the structural instability of the brake assembly.
First, some experiments were carried out in order to grasp the brake squeal phenomenon. These experiments made clear the following items. (1) The low frequency brake squeal occurred at 850Hz. (2) The vibration mode shape had 5 nodes fixed in a space. (3) The brake squeal became maximum at 0.3 - 0.5 (MPa) liquid pressure under the constant temperature condition. (4) The higher the temperature of the pad was, the stronger the brake squeal was under the constant liquid pressure condition.
Second, the numerical analysis method based on the Substructure Synthesis Method was conducted. The modal mass and stiffness of every mode of the disk and the caliper was calculated by FEM, and the reduced dynamic system considered the friction model was calculated by the complex eigenvalue analysis. The analytical results were compared with the experimental ones and they were in good agreement with each other. And it was found that two modes selected among the various modes were coupled with the increase of the friction coefficient, and then the brake squeal occurred. One of two modes was dominated by the disk and the other mode was dominated by the caliper.
Using this method we calculated and surveyed the brake squeal of the actual motorcycle by changing the experimental conditions and studied some countermeasures. One countermeasure was that the vertical stiffness of the caliper attachment was increased and the horizontal stiffness was more or less changed than the present stiffness. Other countermeasures were that the thickness of the disk was changed smaller and that the number of the caliper pod was changed from 6 to 4. The testing using the actual motorcycle was carried out to confirm the effect of those countermeasures. As a result, it was verified that the squeal was reduced as estimated and this analysis method was useful.