Mechanisms of Brake Creep Groan

Creep groan of vehicles is the low frequency chassis vibration occurring at very low brake pressure and extremely slow speeds giving the driver a very uncomfortable feeling. It is the classic example of a self-excited brake vibration caused by the Stick-Slip Effect. The essay discusses the mechanisms leading to self-excitement of vibrations. In the first section of the essay the state of the art is presented by way of a literature investigation and the phenomenon of creep groan is described. Then, by measuring the vibration characteristics of a creep groaning brake it is demonstrated that apart from a tangential brake caliper movement, a twisting of the brake around the vertical axle takes place. This twisting modifies the pressure conditions of the contact areas of brake disk and brake liner.

Based on the measured results of adhesion and sliding coefficients a finite element model is developed simulating the dynamic processes in the friction layer using contact algorithms. Within the scope of a parameter study there is special focus on the physical and tribological properties of the liner and brake components. The simulation results are compared with the measuring results and finally a conclusion is made.