In this work a simplified disc brake model is investigated. It is composed of the two main components involved in squeal: a circular disc and a pad. A hydraulic pressure is applied to the back-plate of the pad to model the braking force. Over the friction interface shared by the disc and the pad, nine uniformly spaced contact elements are introduced and a non-linear contact law is used. Contact and loss of contact configurations are considered. Friction is modeled by the classical Coulomb law with a constant friction coefficient. The stability analysis of this system presents two classical cases of instabilities that are single and multi-instability cases. For both cases, transient and stationary time responses are calculated and compared. Spectrum analysis are performed and harmonic components of the response are detected. To estimate noise emissions during squeal, an acoustic calculation method is proposed. This method is based on the decomposition of the velocity by harmonic component. For each components, the boundary element method is applied and the global pressure wave is obtained by superposition. An acoustic intensity analysis is then performed in terms of levels and directivity. Several observation planes are used and a comparison of acoustic intensity is presented for the single and multi-instability cases. The multi-instability case presents significantly higher levels than the single instability case. In the near field, the directivity patterns for both cases are composed of four main lobes with different shapes and orientations. Moreover, over others observation planes, the multi-instability case presents a more complex directivity pattern due to the participation of two modes in the time response.
Soobbarayen, Kevin; Sinou, Jean-Jacques; Besset, Sébastien; - Laboratoire de Tribologie et Dynamique des Systèmes