COMPUTER SIMULATIONS OF AUTOMOTIVE DISC BRAKE SQUEAL

Abstract

Based on experimental results, we adopted the "decreasing ?k with increasing vs" model as our brake squeal theory and came up with the rubber bushing model to alter the dynamics of the disc brake system. From the rubber bushing model, we developed the two-dimensional mathematical model with six degrees-of-freedom to fully explain the translational displacements x, y and z as well as rotational displacements x, y and z. We define some dimensions of the rubber bushing design and the material properties of the rubber as the input parameters. From these input parameters, we arrive at the in-plane and out-of-plane stiffness coefficient kxy, kz and damping coefficient cxy, cz, known as the base parameters. We further define the vibration frequency, stability time and vibration magnitude as the output parameters. We observed that the in-plane or out-of-plane damping coefficients cxy, cz have no effect on the vibration frequency and the vibration frequency increases as the corresponding in-plane or out-of-plane stiffness coefficients kxy, kz increases. Furthermore, the in-plane stiffness coefficients kxy, have little effect on the stability time and the stability time decreases as the corresponding in-plane damping coefficient cxy or out-of-plane stiffness and damping coefficients kz, cz increases. Lastly, for the vibration magnitude, the in-plane and out-of-plane stiffness coefficient kxy, kz and damping coefficient cxy, cz should be as large as possible for a smaller vibration magnitude. We recommended a best set of input parameters which give the optimum set of output parameters. The corresponding in-plane stiffness coefficient kxy and damping coefficient cxy as well as the out-of-plane stiffness coefficient kz and damping coefficient cz have a value of 720 MNm-1, 322 kgs-1, 1005.3 MNm-1 and 449.6 kgs-1 respectively. Although the vibration frequencies are still within the human hearing range, the resultant in-plane and out-of-plane output parameters have low stability times and vibration magnitudes; which mean that the brake squeal problem should not be present.