Influences of Axle- and Brake Design on Creep Groan Charcteristics

Creep groan is a low-frequency brake noise and vibration phenomenon which is self-excited by nonlinear properties of the friction contact of the brake. Repeated stick-slip transitions in the friction contact between brake pads and disk (or drum) lead to severe vibrations of axle and brake system. These vibrations and the resulting airborne noise are perceived as disturbing creep groan. In this article, the influences of the different axle and brake components are analyzed and discussed on the basis of the vibration patterns occurring during creep groan. Experimental methods such as matrix tests, operational vibration analyses or high-speed video recordings as well as simulative methods such as complex eigenvalue analyses and direct time integration methods are used for this purpose. The investigations, carried out on two different axle setups, provide a comprehensive picture of the mechanisms during various groan phenomena: longitudinal and rotational movements of the axle dominate creep groan displacements. Finally, an evaluation of the influences of the half-axle components provides valuable recommendations for tackling creep groan problems. The presented results can be used both in model building and for understanding and conducting experimental investigations to improve the noise comfort and thus the quality of an automobile.