Influence of Pads and Brake Disc wear on Brake Squeal Noise

The present work aims to investigate the influence of wear of the pads and brake disc on the brake squeal behavior with the help of the Finite Element tool. Brake discs basically work by the pressure of the brake pads against a rotating disc. The friction between the pads and the disc causes the latter to decelerate, but it can also cause dynamic instabilities of the system giving rise to noises. Among the main noise in vehicle brake systems, there is the squeal noise, which is usually associated with the coupling of two neighboring natural modes. One possible way to identify unstable modes is by extracting complex eigenvalues from the system. An unstable mode can be identified when, in the result of the extraction of the complex eigenvalues, the real part of the eigenvalue is positive. In the present work, a brake system (disc and positioned pads and their respective materials and friction coefficients) was duly modeled and validated. The validation was done by means of a correlation between the frequency of the noises found experimentally and the frequency of the unstable modes found in the virtual model. A parametric analysis was performed simulating the wear of the disks and pads to understand the effect of the mass variations and stiffness on the instability of the system. According to the results found in the analyzes that simulate the wear, with the decrease, mainly the thickness of the brake pads, there was an increase of numbers of unstable modes, that is, the brake system is more prone to squeal generation.