The objective of the research are investigations of the low frequency phenomenon creep groan at automotive brake systems with different test rigs, which allows an evaluation of the impact of different influence variables. The accomplished investigations include observations of dynamic friction processes and vibration behaviour by using a tribology test bench, an inertia brake dyno and a vehicle corner test rig. The main purpose of those studies is to understand the physical mechanisms and their influences which cause brake system vibrations at very low vehicle speed. Furthermore there will be studies of the influence of different brake linings on the vibration excitation.
For the investigation and phenomenon description two new test rigs had been developed, in addition to the brake test dyno. Those test rigs enable the user to depict various brake system setups and investigate the impact of those variations on the vibration emission, the sound emission, the body deflection and further phenomena. The different test rigs enable the characterisation of brake component vibration behaviour either of the brake system only, the brake system with an additional steering knuckle (fixed coupling) or the whole vehicle corner. The tribology test rig consists of very few vehicle system parts, so it offers the possibility to analyse the pure stick-slip-phenomenon, while the corner module test rig includes all the elastic elements which can be found at the vehicle suspension. Using the last mentioned test method provides the possibility for investigations including the complete system stiffness effects. Performing those various analyses and post processings on the measurement data helps to understand the influence of individual system parameters and lead to completely new assessment methods.
The results of the investigations are objective insights into the influences of structure stiffness, damping and further system parameters on the creep groan phenomenon. It is now possible to examine the impact of the complexity of the test set-up and the contribution of the individual subassemblies on the sound phenomenon.
In difference to known studies, this study will include a systematic influencing factor rating and point out cross-effects. On this way we are able to point out the influence of the system around the brake. The results of those investigations will be very valuable to the scientific society. We have also the possibility to visualise the movement of the brake system parts respectively the vehicle chassis parts by using 3D-body deflection analysis, high-speed video recording and high-speed microscope analysis.
It is also possible to analyse the vibration transmission (analyse damping coefficients etc.) through the vehicle chassis parts. The mentioned high performance measurement equipment can be used at all different test rigs.
Augsburg Klaus Prof. Dr.-Ing, Hauschild, Peter, Department of Automotive Engineering, TU Ilmenau, Germany; Beierlieb Christian, BMW Group, Germany.