An investigation of brake squeal from a coupled tribology and dynamics perspective

Abstract

Brake squeal is a long-standing problem in the dynamics and tribology fields. This irregular high-frequency noise causes irritation to vehicle users and passers-by, who may believe the brake components are problematic, although the brake system is working as designed. Brake squeal is affected by a number of different factors in micro and macro levels, some of which are not well understood. The aim of this thesis focuses on investigating brake squeal from a coupled tribology and dynamics perspective on a simple point-contact model for a general understanding of brake squeal. The pin-on-disc test rig with a microphone and an infrared camera is adopted and improved to generate a large number of recordable squeals in the laboratory. The experiments are conducted to analyse the effect of the friction process on squeal and the influence of temperature and thermal effects on squeal. In addition, modal analysis is carried out to quantify the vibration characteristics of the uncoupled components. The impact hammer test is a simple and effective method to measure natural frequencies and damping ratios. Sharp and clear peaks in frequency response function are compared with the predicted frequencies, which helps to optimise the material properties in simulation. The scanning Laser Doppler Vibrometer is state-of-the-art equipment that can realize a non-contact 3D vibration measurement and visualize the mode shapes of the disc. These measured mode shapes achieve good agreement with the simulated results. Finally, the dynamic transient method is selected for the instability prediction. The complex eigenvalue method is used to visualize the coupled mode shapes of the pin and disc at the predicted unstable frequencies. This finite element instability prediction model is validated by comparison with the experimentally measured squeals. All the sixteen squeal frequencies recorded experimentally are successfully predicted by the dynamic transient analysis on the hemisphere and disc model.