Impact of contact stiffness heterogeneities on friction-induced vibration

It is well-known that the occurrence of squeal depends on numerous phenomena still relatively unknown. Furthermore, squeal is affected by several factors on both the micro and macro scales. The present paper proposes some potential interactions between stiffness heterogeneities of the contact surface and the potential for triggering the squeal. Consequently, an analytical model has also been developed to highlight the impact of certain parameters on the squeal phenomenon. The contact surface has been modeled by connecting the disc with the pad via distributed springs (contact stiffness). From this model, a static equilibrium and a complex modal analysis were performed to determine respectively the pressure distribution and the natural frequencies of the system. In this configuration, the results demonstrate that the introduction of heterogeneities could change the dynamic behavior of the system. Moreover, the influence of the size of the heterogeneities was studied and results show that this parameter had an influence on the likelihood of squeal occurrence. The paper also points out a heterogeneities correlation length that is reasonable to consider for this special configuration. Such information is relevant when interpreting the occurrence of noise as a function to the sizes of the components of the brake pad and the morphology of the surfaces in contact.