Experimental investigation on brake squeal unpredictability: role of the friction noise

Dynamic contact instabilities represent a common issue in brake industry, causing noise and passenger dissatisfaction. Past works identified mode coupling as the cause of brake squeal, but the conditions for its occurrence are still not fully understood, making this phenomenon hardly predictable. This work investigates the relationship between the friction noise, intended as the dynamic excitation generated by the local interface interactions (ruptures, impacts …), and the unstable response of the system. An experimental measurement campaign, conducted on a dedicated tribometer, highlighted that, even in presence of the same macroscopic friction coefficient, mode coupling instability occurred only when in presence of high values of friction noise. Therefore, the friction noise is proposed as a trigger factor for brake squeal occurrence.