Abstract
KEYWORDS – NVH, nonlinearity, joints, contact interface, testing
ABSTRACT - Brake systems contain a plethora of frictional interfaces and joints. This implies nonlinearity in the system due to friction, clearances and varying contact areas. Although joints are well-known to be a source of nonlinearity and variability, today they still appear to be largely overlooked by the brake community and the lining material is considered the major source of the nonlinear, variable system behaviour. This contribution aims at demonstrating the impact of joints on the system dynamics and deals with the experimental analysis of a brake sub-structure (including joints) as well as the characterization of the system-immanent nonlinearities. For this purpose a test setup consisting of calliper, carrier and pad is defined and shaker measurements are conducted. Modal characterization functions as an approach for describing nonlinearities as well as load history effects are discussed. The results indicate a significant impact of joints on the dynamic behaviour of the sub-structure. Resonance frequencies as well as damping levels strongly depend on the excitation level. Furthermore, load history effects can be observed. This article discloses that frictional interfaces and joints introduce significant nonlinear behaviour and variability, e.g. in terms of load history effects, to brake systems. Thus, joints should be considered when discussing brake noise arising with increasing run time. Consequently, joints in brake systems should be evaluated as noise, vibration, harshness (NVH) design elements rather than merely as structural necessities.
ACKNOWLEDGEMENT Part of the funding for the presented study is provided by Audi AG and AiF in the context of Cooperative Industrial Research (IGF) grant no. 16799N.