Effects of Surface Roughness on Automotive Brake Squeal Ashwin Kumar, F. Sadeghi, C.M. Krousgrill Sponsor: Robert Bosch GmbH

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1 Effects of Surface Roughness on Automotive Brake Squeal Ashwin Kumar, F. Sadeghi, C.M. Krousgrill Sponsor: Robert Bosch GmbH Objectives: Analytical studies on the effects of surface topography on stiffness of contact between rough bodies and consequently on the dynamic stability of brake system vibrational modes. An approach to noise prediction relies on numerical studies of the eigenvalues of the coupled brake system. The stiffness of coupling between the rotor and backing plates is affected by the surface topography of the friction material. Work to date has focused on studying this coupling stiffness via numerical simulations of rough surface contact. Future work will incorporate the resulting spatially and load dependent stiffness behavior into existing squeal prediction models. surface topography load - deflection curves

2 Investigation of Friction Forces at the Nanoscale Bill Conley, A. Raman, C.M. Krousgrill Sponsors: National Science Foundation, DOE CSGF Typical atomic force microscope in torsion A=0.5 A=1.5 <F> 0.5 Friction vs. Velocity Curve for nanoscale friction Omega Recent development of the atomic force microscope allows for an experimental and theoretical investigation of lateral forces acting in near point contacts. Nonlinear nature of friction allows for conservative interactions to produce dissipative forces.

3 Analytical and Experimental Studies of Automotive Brake Squeal David vanderlugt, C.M. Krousgriil and F. Sadeghi Sponsor: Robert Bosch GmbH Objective: Integration of squeal vibration response measurements to develop improved analytical models for the prediction and reduction of squeal vibrations in automotive braking systems. analytical stability analysis Validation of finite element component models through modal testing. Experimental studies of friction material mechanical properties: COF, compressive force-deflection, contact roughness profiles. Correlation of noise events from full scale brake system test rig with results from analytical stability analysis. Refinement of squeal prediction model. squeal exp. squeal response squeal response

4 Modeling of Drum Brakes for Squeal and Sensitivity Analysis Jinchun Huang,C.M. Krousgrill, A.K. Bajaj Sponsor: Isuzu Motor Company, Ltd. Objectives: To develop an understanding of system parameter sensivities to the onset of brake squeal and to develop methods to reduce squeal. Methods: Numerical modeling; complex eigenvalue analysis; sensitivity analysis; design optimization. Results: Modes with small separation and compatible mode shapes tend to cause squeal. Onset of squeal can be accurately predicted by a two-mode model. Lining shape has significant influence on onset of squeal. Structural optimization can be applied directly to model for reduction of squeal vibrations.

5 Vibrations of Spiral Bevel Geared Systems Rex Mennem, C.M. Krousgrill Sponsors: National Science Foundation, Caterpillar Inc. Objectives: To develop theoretical model for gear mesh vibrations and to provide an understanding of the influence of parametric excitation on dynamic response. Complete axle assembly model developed using combination of finite element analysis, experimental techniques and energy approach. Implementation of improved methods for predicting parametrically-excited response. Observation of increase of unstable response during low torque operation due to decrease in mean mesh stiffness. Observed increase in higher frequency parametric excitation resulting from meshing gears.

6 Analysis and Measurement of Squeal Vibrations in Glass Run Sealing Systems Uije Kim, C.M. Krousgrill, L. Mongeau Sponsors: AES, Decoma Analysis of squeal vibration using spectrogram tools. Response period elongation at onset of squeal shows strong contribution of stick-slip oscillations in response. Nonlinear FEM static analysis to simulate contact between seal and glass. FEM frequency analysis to extract the mode of squeal vibration. Friction-coupled model using FEM component modes and nonlinear friction law. Frequency Objective: Determination of the mechanism of squeal vibrations in automotive glass sealing systems under wetted conditions and development of analytical models to be used to reduce occurrence of squeal. Time