Influence of geometry imperfections on squeal noise linked to mode lock-in

Numerical studies of squeal in brake systems are carried out with unreal perfect surfaces. In this paper, a methodology to introduce geometric imperfections in the multi-scale contact problem is proposed. Two kinds of geometric imperfections are taken into account separately: the first is “disc thickness variation” as function of the disc while the second is the “plateau” as function of the friction pad. A complete resolution strategy is proposed with a combination of finite element analysis and a lumped-mass model for a simplified pin-on-disc system. A complex modal analysis is performed for different static configurations in which only the contact pressure evolves. Parametric studies for both cases are performed to study the influence of these geometric imperfections on mode lock-in. It is shown that the introduction of both kinds of geometrical imperfections have an influence on dynamic behavior and mode lock-in (through modification of the eigenfrequencies of the system). The pad mode is mostly influenced by bumping which modifies the contact localization. Considering plateaus on the pad surface highlights the importance of the theoretical contact length parameter.