Brake Creep Groan Noise - Vibration Mechanism and Simulation

Authors

Prof. Peter Fischer, Dipl.-Ing. Manuel Pürscher, Dipl.-Ing. Severin Huemer-Kals, Institute of Automotive Engineering, Graz University of Technology, Graz

Summary

Creep Groan is an impulsive brake noise at creep velocities of the vehicle. Stick-slip between brake disc and brake pads is an important trigger of creep groan. Flexibilities in the axle bushings, elastic deformations of suspension parts and the wheel movements facilitate the nonlinear, periodic signature of creep groan vibrations.

Frequently, creep groan occurs around 15 - 20 Hz and 70 - 90 Hz. The mechanism at 15 - 20 Hz is classical stick-slip. At 70 - 90 Hz, the vibrations are typically in a transition between stick-slip and rotational vibrations without sticking, i.e. at relative speeds between disc and pads in the same direction. In practical vehicle operation, the range of 70 - 90 Hz is the most relevant one.

The simulation by complex modal analysis (CEA), which is a well-established tool for squeal analysis, requires extensive linearisations. These appear not suitable for creep groan phenomena involving distinctive stick phases. For dynamic response analysis in time domain, both implicit and explicit computation methods can be used. However, for larger Finite Element models above some thousand elements, the explicit solution scheme shows clear advantages in terms of computation times and in view of a straightforward procedure for industrial application.

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