Abstract
Comfort is one of the main indicators of passenger vehicles quality and therefore reduction of the noise level of brake systems is a key aspect to achieve customer’s quality aspirations. Brake squeal is the most common noise problem and also the most studied one by brake NVH researchers. Despite the huge effort done to solve it, squeal remains an unresolved problem due to the fugitive nature of squeal which may happen or not in apparently the same working conditions. In addition the combination of several components in real brake systems, such as piston seal, which changes system behaviour makes the squeal more difficult to analyze. In order to avoid the combination of different factors, simplified testing set ups are made with only essential and simple geometry components needed to reproduce squeal. With these experimental rigs some of the factors that have influence on the fugitive nature of squeal are can be controlled and higher repeatability can be achieved. Moreover, due to the compact design of real brake systems, sensing can also be tricky while simplified test set ups are designed focusing on system sensing. One advantage of simplified set ups is the possibility to vary parameters like damping or stiffness that have influence on squeal generation. In the present work a simplified test set up is presented which is composed of a rotating disc and reduced area pads machined out from commercial brake pads. Brake pads are held in tangential direction by a H shaped part and the contact pressure between pads and disc is performed with a plate. These two parts provide tangential and axial stiffness respectively, which in real brake system are provided by anchor bracket and caliper housing. In the present work the influence of the tangential and axial stiffnesses on squeal generation is studied modifying the thickness of both. Squeal noise is measured with a microphone and related with the vibration frequencies acquired with triaxial accelerometers located in brake pads. Moreover, the evolution of the friction coefficient can be obtained with strain gauges located at the tangential plates.
KEYWORDS – Brake noise, Squeal, Simplified test, Experimental, Stiffness