Complex Modal Analysis on a Disc Brake with Thermal Deformation and Rough Surfaces

Braking squeal is still a challenging problem and attracts many attentions even today. With a specific disc brake for passenger vehicles, this paper addresses the influence of the contact status between the pad and disc, with a focus on the surface roughness and thermal deformation. Experiments were carried out for surface profile of the braking pad, the thermal and mechanical parameters of the pad materials, including friction coefficients under various conditions. Random rough surfaces were generated for the braking pad based on the measured profile. Temperature field and thermal deformation of the pad were obtained by means of finite element analysis. A spatial FFT method was adopted to calculate the pressure distribution on the deformed rough surface. Complex modal analysis was then conducted on the brake system with thermal deformation and the unevenly distributed pressure from rough profiles, so as to predict the occurrence of braking squeal according to the unstable modes. Observations made from the numerical results are illuminative for future study.