The improvement of the noise behaviour in brake disc system is a competitive challenge factor for CBI with an increasing customer requirement for comfort in passenger car. One NVH concern and very known phenomena is the squeal which is now less and less tolerate in premium car applications. Brake squeal occurs if disc brake system meet an unstable condition which can be linked to the geometry(linked to eigen frequency distribution) system stiffness ,dynamic μ and damping level. Our objective is to find an optimize casting process parameters and to propose a change of cast iron properties to reach damping level target in our disc brake components.
Many publications exist on damping behaviour of cast iron. The majority of them deals with damping characteristics and microstructural influences in GJL-type cast irons that means cast iron with lamellar graphite morphology. A smaller amount of publications deals with damping structure of graphite with nodular graphite shape.A good overview on damping in metals, alloys and metal matrix composites is given by J Zhang (J.Zhang, R.J.Perez "effects of secondary phases on the damping". It can be found that the main reason for the damping in ductile cast iron is the friction in the interface between graphite and matrix.. No influence of the matrix structure on damping was determined. Some of research were coming from our multi-dimensional study performed on disc brake component which has shown that structure of cast iron had an impact on damping but not only ,casting process parameters could increase the damping level in cast iron.
Thierryl Chancelier, Pasquet Thierry, Vanessa, Ruzicic, Philippe Eble - Chassis Brakes International