Browse Publications Technical Papers 2018-01-1872
2018-10-05

A Study on Trigger of Small Friction Noise in Disc Brake Squeal 2018-01-1872

It is well known that brake squeal is caused by flutter of dynamic unstable system under small disturbance. Therefore the research of small disturbance is very important technical issues for disc brake squeal reduction. The experimental set-up for basic research was developed based on the actual disc brake squeal vibration mode in experiment and its theoretical analysis, which replaces cantilever type pad-caliper from actual caliper and pads. Disc brake squeal depends on the natural frequency of cantilever type pad-caliper, which were caused at 2.7kHz, 2.0kHz and 5.3kHz for each cantilever length L=40mm, 50mm and 80mm in each friction test. In friction test L=40mm and 50mm, cantilever type pad-caliper vibrates with the 1st order bending vibration mode and disc vibrate with the 1st or 2nd order bending vibration mode. In friction test L=80mm, cantilever type pad-caliper vibrates with the 2nd order bending vibration mode and disc vibrates with the 4th order bending vibration mode. Theoretical analysis for these experimental results are shown in this research. The vibration modes in each brake squeal are not same, then each friction point behaviour per 1 cycle during brake squeal generation is almost same oval shape not line. These simulation results mean the same mechanisms of dynamic energy increase. On the other hand, small friction noise was caused around 1 kHz in this friction test of cantilever length L=80mm, then its cantilever type pad-type caliper vibrates with the 1st order bending vibration mode but disc vibration amplitude is so small. This friction noise 1 kHz is considered to be self-excited vibration in friction coefficient dm/dv<0, which depends on not only friction characteristics but also the natural frequencies of cantilever type pad-caliper and disc. Brake squeal is considered to be triggered by small friction noise. Accordingly, brake squeal can be reduced by reduction of small friction noise.

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