ANALYSIS OF DISC BRAKE NOISE USING A TWO-DEGREE-OF-FREEDOM MODEL

Although a brake pad and disc have many modes of vibration, when it is unstable and hence noisy then frequently only a single mode of the complete system contributes to the vibration. In this condition, only a few modes are required to model the system. In this paper, a two-degree-of-freedom model is adopted where the disc and the pad are modelled as single modes connected by a sliding friction interface. Using this model, the interaction between the pad and the disc is investigated. Stability analysis is performed to show under what parametric conditions the system becomes unstable, assuming that the existence of a limit cycle represents the noisy state of the disc brake system. The results of this analysis show that the damping of the disc is as important as that of the pad. Non-linear analysis is also performed to demonstrate various limit cycles in the phase space. The results show that the addition of damping to either the disc or the pad alone may make the system more unstable, and hence noisy.