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Vehicle Wind Buffeting Noise Reduction via Window Openings Optimization

NAE, Ford Motor Company-F. Chen, P. Qian
Published 2008-04-14 by SAE International in United States
Vehicle wind buffeting noise occurs when one window of a vehicle is opened in a certain way during driving. By optimizing window openings, the buffeting noise can be significantly reduced or may be even eliminated. In addition, the optimized window openings will also provide sufficient fresh air circulation while allows the driver still be able to enjoy listening to radio. This paper provides such an optimization and describes the principle with the results from both laser imaging and road tests.
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Disc Brake Squeal: An Overview

NAE, Ford Motor Company-F. Chen
Published 2007-04-16 by SAE International in United States
Understanding, reducing, eliminating and preventing brake squeal is a challenging task. It involves many design variables in a complex brake system and there are many harsh operational and environmental conditions under which squeal may occur. Much progress has been made on understanding brake squeal mechanisms and causes. Squeal simulation and analysis methods have been significantly advanced. The evaluation and testing technologies have been noticeably improved, and reduction remedies and prevention measures have become more mature. Brakes have become much quieter. However, the recurring occurrence of disc brake squeal indicates that there are still many challenges ahead and brake squeal is still an elusive quality issue. This overview provides the summary of some current developments and discusses remaining challenges along with future technologies. In addition it emphasizes the real world counter measures for squeal reduction, elimination and prevention.
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Brake Pad Modal Characteristic Measurement and Analysis

Research and Vehicle Technology Ford Motor Company-F. Chen, A. Wang, J. Bloomer
Robert Bosch Corporation-M. Yang
Published 2005-10-09 by SAE International in United States
The modal characteristics of a brake pad are important factors affecting brake squeal. The most frequently used counter-measures for eliminating or reducing squeal, especially at high frequency, are the modification of: the modal frequencies, damping, contact modal shapes or patterns of a pad by making a chamfer or slot, or selecting a different under-layer, lining material or insulator.This paper describes the development of the methods for the measurement of pad modal characteristics such as modal damping, frequency and contact mode shape. It provides comparison among three methods: accelerometer-hammer, laser-hammer, and laser/non-contact shaker with test data and CAE simulation. Subsequently, laser/non-contact shaker was used to evaluate the process capability of pad manufacturing in terms of modal damping and natural frequency. This method was also employed to investigate the effect of pad chamfer, under-layer and the insulator on pad modal characteristics. An example is provided on reducing squeal by increasing pad damping. Lastly, the method for contact mode shape measurement is provided.
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Nanometer Displacement Measurement Using High Magnification Diffraction Imaging

Ford Motor Company-F. Chen, P. Harwood
Oakland University-L. X. Yang
Published 2005-04-11 by SAE International in United States
This paper proposes a direct nanometer measurement method using the technique of high magnification diffraction imaging. The principles of employing both gratings and speckles are described, in which the illumination distances that generate high magnified and focused images are discussed along with demonstration test results. In addition, the potential extension to sub-nanometer displacement measurement is discussed.
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Suppression of Self-Excited Vibration by Dither Technique with Potential Application to Reduce Brake Squeal

Research and Vehicle Technology, Ford Motor Company-F. Chen, A. Wang
Wayne State University-C. A. Tan
Published 2004-10-10 by SAE International in United States
Disc brake squeal is a manifestation of the friction-induced self-excited instability of the brake system. One of known techniques in suppressing dynamic instabilities in nonlinear systems is by applying dither. The focus of this paper is to examine, through numerical examples, the feasibility and effects of dither on nonlinear systems as a means of quenching large-amplitude limit cycles. In particular, various ways of introducing the dither, either via modifications of the system characteristics or as external excitation, are explored. The investigation is extended to a disc brake system using finite elements simulations. Numerical results show that large-amplitude vibrations can be suppressed by dither and careful tuning of the amplitude and frequency of the dither can result in an effective quenching. The potential application of this technique to disc brake squeal control is also discussed.
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Measurement and Analysis of Rotor In-plane Mode Induced Disc Brake Squeal and Beyond

Ford Motor Company-F. Chen, D. Mckillip
TRW Automotive-J. Luo
Published 2004-10-10 by SAE International in United States
This paper provides measurement and analysis on rotor in-plane mode induced squeal. Methodology is presented to simultaneously acquire both temporal and spatial squeal operational deflection shapes (ODS). Rotor accelerations both in the in-plane and out-of-plane directions were measured during squeal along with rotor's normal ODS using a laser vibrometer. Modal measurement and analysis of the rotor and pad in the in-plane and out-of-plane directions were conducted as installed in system condition. The test results indicating rotor modal coupling in the in-plane are provided, and out-of-plane directions, and conclusions on in-plane mode induced squeal are proposed. In addition, the countermeasure for squeal reduction is discussed.
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On Automotive Disc Brake Squeal Part IV Reduction and Prevention

NAE, Ford Motor Company-F. Chen, H. Tong, S. E. Chen, R. Quaglia
Published 2003-10-19 by SAE International in United States
This paper as part IV of a series articles first very briefly reviews squeal generation process in terms of energy transfer. A squeal reduction and prevention cascade chart including various contribute elements is formed. Subsequently, variation ranges of some key parameters of brake components and system due to manufacturing processes and operational/usage condition changes are given. Design concept of a broad stable and less vibration brake system is proposed and addressed in light of these variations. Robust design criteria and strategies are discussed. Design tools and methods are summarized. At last, some application examples are provided.
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On Automotive Disc Brake Squeal Part III Test and Evaluation

NAE, Ford Motor Company-F. Chen, J. Swayze
Robert Bosch Corporation-M.K. Abdelhamid, P. Blaschke
Published 2003-05-05 by SAE International in United States
This article, as part III of a series, briefly reviews some of the representative literature on brake squeal testing and evaluation. It discusses the potential influence of variation within brake components and operational conditions on brake squeal dynamometer tests and their correlation to vehicle road tests. Roles and challenges of component/system parameter measurements such as brake pad damping, disc rotor in-plane mode and friction induced vibration characteristics, friction coefficient, moisture absorption and elastic constants of lining material, and contact stiffness are addressed. An application example of a reliability method to assure dynamometer test results are statistically significant is presented. The advantages of using laser metrology are also briefly described, especially the measurement of 3D squeal operational deflection shape. Lastly, general future research directions are outlined.
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On Automotive Disc Brake Squeal Part I: Mechanisms and Causes

Department of Mechanical Engineering, Wayne State University-C. A. Tan
NAE, Ford Motor Company-F. Chen, R. L. Quaglia
Published 2003-03-03 by SAE International in United States
The understanding, prediction and prevention of brake squeal is a difficult and challenging problem because of the large number of design variables involved in a complex brake system and many operational and environmental conditions under which squeal may occur. The design variables may have different optimal values and different contribution trends for different brake systems. Since the 1930's, much progress has been made in gaining physical insight into brake squeal mechanisms and causes, and brakes have become quieter. However, the recurring occurrence of disc brake squeal indicates that our understanding of the phenomenon is both insufficient and incomplete, and that brake squeal is still a quality issue in the automotive industry and its prevention is far from reality. Part I of this series of articles first reviews the various hypotheses put forth for brake squeal mechanisms and causes. Subsequently, it discusses some refined thoughts, and new results obtained from recently developed test/analysis methods by which the unified hypotheses are proposed.
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Modal Coupling and Its Effect on Brake Squeal

Research and Vehicle Technology, Ford Motor Co.-F. Chen, J. Chern, J. Swayze
Published 2002-03-04 by SAE International in United States
More evidence has been found that rotor in-plane mode(s) and out-of-plane mode(s) alignment and coupling are the primary and inherent root cause for a disc brake to generate squeal at high frequencies. Eight different vehicles with different rotors have been tested considering known squeals. It has been found that the squeal frequencies are at the rotor in-plane mode(s) and out-of-plane mode(s) alignment and coupling frequencies. Rotor modal test results, vehicle squeal frequencies, and CAE operational simulation are presented.
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