Investigation of the chatter and squeal phenomenon in bicycle disc brakes

Master thesis (2022)

Authors

A. Ajaypal Singh Mechanical Engineering

Contributors

J.K. Moore Biomechatronics & Human-Machine Control - Mechanical, Maritime and Materials Engineering (supervisor 1)
Faculty
Mechanical Engineering
Copyright: © 2022 Ajaypal Singh
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Published Date

22-08-2022

Language

English

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Faculty

Mechanical Engineering

Abstract

Bicycle disc brake noise and vibration, which usually falls in the frequency range of 0-2 kHz, is a principal braking quality attribute that has started to attract significant interest from bicycle manufacturers. Brake noise is an irritant to their customers, who see it as a symptom of a defective brake and that leads to unnecessary warranty claims.

Over the years various theories (e.g. stick-slip, sprag-slip, modal coupling) have been developed that explain the noise and vibration generation mechanism in the frictional brakes. Traditionally, research groups working on this issue have conducted their investigations by combining analytical and experimental studies. Likewise, this report aims to predict the brake noise using finite element analysis where the experimental data validates the finite element model.

In order to reproduce the brake noise in the laboratory setting, the brake test machine at the Koninklijke Gazelle laboratory was used. This novel test bench made it possible to run the experiments on the actual bike by providing features to control the bike speed, brake pressure, and weather conditions within the setup. The dynamic characteristics of the brake system were captured with the microphone and the laser Doppler vibrometer. % The audio frequency spectrum was generated by placing a microphone close to the sliding interface of the pads and rotor. A Laser Doppler vibrometer was used to generate the mode shapes and the vibration velocity spectrum of the brake components.
It was established from the results of the brake noise audio and the vibrometer scans that the entire bike vibrated at three peak frequencies during the brake noise events. Brake noise level as loud as 95 decibels was captured. Stick-slip as one of the friction-induced instabilities was identified during the experiments.

Furthermore, a detailed finite element model of the disc brake assembly was developed. Modal analysis on the components of the assembly and a pre-stressed modal analysis on the entire brake assembly was performed. The finite element results compared well with the experimental results. It was observed that there exists doublet modes and intermediate modal coupling in the system.

Limiting the rotor symmetry by adding weights on the rotor ribs was shown to be effective in reducing instabilities. Other ways to counter brake noise by increasing the rotor mass and by introducing a parallel slot in the brake pad were successfully tested.