Theoretical and experimental investigations of the bifurcation behavior of creep groan of automotive disk brakes

There are several low frequency vibration phenomena which can be observed in automotive
disk brakes. Creep groan is one of them provoking noise and structural vibrations of the
car. In contrast to other vibration phenomena like brake squeal, creep groan is caused by
the stick-slip-effect. A fundamental investigation of creep groan is proposed in this paper
theoretically and experimentally with respect to parameter regions of the occurrence. Creep
groan limit cycles are observed while performing experiments in a test rig with an idealized
brake. A nonlinear model using the bristle friction law is set up in order to simulate the limit
cycle of creep groan. As a result, the system shows three regions of qualitatively different
behavior depending on the brake pressure and driving speed, i.e. a region with a stable
equilibrium solution and a stable limit cycle, a region with only a stable equilibrium solution,
and a region with only a stable limit cycle. The limit cycle can be interpreted as creep groan
while the equilibrium solution is the desired vibration-free case. These three regions and
the bifurcation behavior are demonstrated by the corresponding map. The experimental
results are analyzed and compared with the simulation results showing good agreement.
The bifurcation behavior and the corresponding map with three different regions are also
confirmed by the experimental results. At the end, a similar map with the three regions is
also measured at a test rig with a complete real brake.