Institute of Engineering and Computational Mechanics
Contact Problems in Multibody Dynamics
Simulations and experiments to investigate brake squeal
Friction between elastic bodies in relative sliding motion often causes high frequency noise problems in dynamic structures, e.g. braking systems. Objective of this work is the calculation of the structural dynamics of brake systems aiming at prediction of brake squeal noise. Based on measurements the work is done with the method of Elastic Multibody Systems (MBS).
The first approach for this project is a simplified brake system. It consists of a flexible pin in contact with a rotating flexible disc. The elastic bodies are described by moving reference frames for the nonlinear motions and by a Ritz approach for the superimposed linear deformations. The corresponding mode shapes are obtained from Finite Element calculations. In order to decrease the computation times, a modal condensation is applied and eigenmodes up to 10 kHz are chosen to describe the elastic behaviour involved in 2.2 kHz squeal. For contact modelling a sliding coordinate frame on the disc surface is formulated and included in the SIMPACK software.
To verify the numerical model, experimental work on a pin-on-disc test rig is conducted. The results of vibration measurements with a Laser Doppler Vibrometer confirm the numerical calculations: Friction in the disc plane leads to an instability of the steady sliding state. Numerically, the instability can be detected with a complex eigenvalue analysis of the steady sliding state and the nonlinear finite-amplitude limit-cycles are obtained by time integrations using the MBS code.
Schroth, Ruediger: Presentation: An Elastic Multibody System Approach
for Friction Induced Vibrations. Zuerich: GaMM, 2001.