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Brake Noise Reduction on a Heavy-Duty Vehicle Using Rotor Asymmetry
Published October 22, 2006 by Society of Automotive Engineers of Japan in Japan
This paper considers the introduction of asymmetry onto a heavy-duty commercial disc brake to alleviate an undesirable high amplitude noise at 2400 Hz, the rotor vibrating with a 5-diametral mode order. It is shown that by adding mass to the free-free mode of vibration the amplitude at the undesirable frequency is reduced considerably and a mode split is observed.
Increasing the asymmetry shows the frequency split to increase from a few hertz to several hundred. A test rig is used to determine the full effect of the staged modifications when it is seen the noise is eliminated. On-vehicle tests demonstrate the effectiveness of the technique when it is seen the condition goes from one where the vehicle cannot travel a few meters without excessive noise to a situation where the vehicle passes whole day trials without a noise issue. It is seen that under normal driving conditions thermal concerns have not been an issue. In the first instance asymmetry is introduced by drilling holes, radially, into the disc blade but a bespoke cast disc is produced which exaggerates asymmetry, the resulting frequency split being 769 Hz.
Finite element analysis complements the experimental results where it is seen that the two normal modes split with one of the rotor modes positioned at the location of the drilled holes whereas the second is located between the holes.