1、Disc Brake Squeal Mechanism, Analysis, Evaluation, and Reduction/Prevention Frank Chen, Chin An Tan, Ronald L. QuagliaDisc Brake Squeal Mechanism, Analysis, Evaluation, and Reduction/PreventionOther SAE titles of interest: Advanced Brake Technology By Bert Breuer and Uwe Dausend Order No. R-352 Brak
2、e Design and Safety: Second Edition By Rudolf Limpert Order No. R-198 For more information or to order a book, contact SAE at 400 Commonwealth Drive, Warrendale, PA 15096-0001 Phone (724)776-4970; Fax (724) 776-0790 Email: CustomerServicesae.org Website: http:/store.sae.org.Disc Brake Squeal Mechani
3、sm, Analysis, Evaluation, and Reduction/Prevention Frank Chen, Chin An Tan and Ronald L. Quaglia Warrendale, Pennsylvania USA Copyright 2006 SAE International eISBN: 978-0-7680-5457-6All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in
4、any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. For permission and licensing requests contact: SAE Permissions 400 Commonwealth Drive Warrendale, PA 15096-0001-USA Email: permissionssae.org Tel: 724-772-4028 Fax: 7
5、24-772-4891 Library of Congress Cataloging-in-Publication Data Disc brake squeal : mechanism, analysis, evaluation, and reduction/prevention / edited by Frank Chen, Chin An Tan, and Ronald L. Quaglia. p. cm. Includes bibliographical references and index. ISBN 0-7680-1248-1 1. Motor vehiclesDisc brak
6、esVibrationPrevention. I. Chen, Frank. II. Tan, Chin An. III. Quaglia, Ronald L. TL269.D57 2006 629.246dc22 2005056307 SAE 400 Commonwealth Drive Warrendale, PA 15096-0001-USA Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA) Fax: 724-776-1615 Email: CustomerServicesae.org Co
7、pyright 2006 SAE International ISBN 0-7680-1248-1 SAE Order No. R-353 Printed in USAPreface The braking process in an automobile involves the contact of metallic solids sliding against each other, which sometimes generates undesirable noise, vibration, and harshness. Brake noise causes discomfort to
8、 passengers and degrades their perceptions of the quality of the vehicle. With todays vehicles so refined and other types of vehicle noise significantly reduced, brake noise and vibration are becoming more perceivable by owners, leading to high warranty costs. With extensive research on brake noise
9、already reported in the literature, the focus of this monograph is to provide a state-of-the-art summary on the modeling, analysis, and prevention of noise generated in disc brakes, generally called disc brake squeal. Since the early twentieth century, many investigators have examined this problem b
10、y analytical, computational, and experimental methods. With the advance of computers and laboratory equipment, significant resources have been devoted to reducing or eliminating disc brake squeal, as evidenced by the strong attendance at the recent Annual SAE Brake Colloquia. However, disc brake squ
11、eal remains an elusive problem, and there is not yet a method to completely suppress it. Brake squeal is an annoying, usually single-tone, and high-pitched noise. The fre- quency at which it occurs may vary from about 1 to 20 kHz, This frequency range is divided into low (1 to 3 kHz), mid (3 to 6 kH
12、z), and high (6 to 20 kHz), with the human hearing ability cut-off at about 20 kHz. Brake noise below 1 kHz is often characterized as groan, moan, or grind. This is caused by the sliding contact mechanics in braking, but it also de- pends strongly on the modal characteristics of suspension systems.
13、Brake squeal can occur at any temperature and with or without the presence of humid conditions. When squeal happens only in the morning because of overnight brake environmental conditioning, it is often called morning sickness/squeal. A cold squeal tends to occur at low speed with low braking pressu
14、re. A hot squeal most likely occurs when a brake is cooling down after warm-up periods. These characteristics have been observed in laboratory and road tests, and engineers and researchers have made progress (though sometimes at an incremental pace) toward understanding squeal generation and develop
15、ing an integrated, cost-effective approach to designing quieter brakes. The modeling and analysis of disc brake squeal is a challenging multidisciplinary problem in mechanics at both macro- and microscopic levels, involving contact mechanics, nonlinear dynamics and vibration, acoustics, and tribolog
16、y. From a nonlinear dynamics viewpoint, it is generally believed that brake squeal is a friction-induced, self-excited phenomenon. Despite the large number of design variables that may vary during braking processes and the complexity of the problem, significant advances have been made in vvi every a
17、spect of researchfrom understanding the fundamental mechanisms of squeal to disc brake design optimization. While these results have been published in a wide variety of resources, there is no single volume that summarizes the state-of-the-art development and progress made by academic and industrial
18、researchers. It is with this motivation that we decided to consolidate recent results in squeal mechanism, identification, analysis, test evaluation, design, and prevention by internationally renowned researchers and engineers, from both the academia and industry, into this collection. The chapters
19、of this book are arranged in the order of mechanisms and causes, model- ing and analysis, testing and evaluation, and design and prevention strategies. An overview of mechanisms of brake squeal is summarized in the first chapter, with emphasis on recent developments. Modeling of contact mechanics an
20、d dynamic analyses of brake squeal are given in Chapters 2 to 7. The analysis techniques include moving load and parametric ex- citation formulations, complex modal and nonlinear time domain analyses, and rotor mode characterization, with emphasis on the discussion of the instability of disc brake s
21、ystems as the primary cause for brake squeal. Chapters 8 to 14 summarize the recent developments in brake pad damping design, brake dynamometer and road tests, laser metrology, and appli- cation of a state-of-the-art signal processing methodthe Empirical Mode Decomposition (EMD) techniqueto understa
22、nd brake squeal. The EMD technique was developed by NASA and has been called one of their most promising technologies. Robust design ap- proaches on brake squeal reduction and prevention are discussed in the last chapter. The book also collects more than 350 recently published literatures. We would
23、like to acknowledge the following contributing authors (listed alphabeti- cally) for their efforts and willingness to share important data and information with the brake community. Of particular significance, we regret the loss of our dear colleague, Dr. Wayne Nack, who passed away in early 2005. We
24、 trust that his contribution to this monograph will reflect his long-lasting impact on the brake squeal research community. Mohamed K. Abdelhamid, Ph.D. Technical Manager, Robert Bosch Corporation Shih-Emn Chen, Ph.D. Senior Technical Specialist, Ford Motor Company Frank Chen, Ph.D. Adjunct Professo
25、r, Wayne State University; Technical Leader, Ford Motor Company Eric Denys, Ph.D. NVH Technical Manager, Material Science Corporation Andreas Ettemeyer, Ph.D. Founder, Ettemeyer GmbH their professionalism has allowed this monograph to be published in a timely fashion. Frank Chen, Ford Motor Company,
26、 Dearborn, MI Chin-An Tan, Wayne State University, Detroit, MI Ronald L. Quaglia, Ford Motor Company, Dearborn, MI September 2005Contents CHAPTER 1 Mechanisms and Causes of Disc Brake Squeal 1 C. A. Tan and F. Chen CHAPTER 2 Contact and Interface Dynamics 27 W. W. Tworzydlo CHAPTER 3 Parametric Vibr
27、ation Induced by Moving Loads 49 H. Ouyang CHAPTER 4 Complex Modes: Analysis and Design 79 W. V. Nack and S.-E. Chen CHAPTER 5 Complex Eigenvalue Analysis of Friction Moment-Induced Mode Coupling in One- and Two-Dimensional Models 95 J. Flint CHAPTER 6 Nonlinear Vibration, Instability, and Brake Squ
28、eal Operation Simulation 131 F. Chen, A. Wang, and C. A. Tan CHAPTER 7 Vibration of Disc Brake Rotors. 161 J. A. Wickert CHAPTER 8 Brake Pad Damping: Measurement, Design, and Application 187 E. Denys, M. Yang, and F. Chen CHAPTER 9 Dynamometer Testing 215 J. K. Thompson CHAPTER 10 Los Angeles City T
29、raffic (LACT) Testing 229 M. K. Abdelhamid and E. Denys ixx Contents CHAPTER 11 Noise Dynamometer and Vehicle Test Correlation 249 J. Luo and A. Lock CHAPTER 12 Friction Materials Elastic Constant Measurements 273 D. E. Yuhas and M. P. Yuhas CHAPTER 13 Empirical Mode Decomposition Analysis Technique
30、 309 C. A. Tan, F. Yang, and F. Chen CHAPTER 14 Laser Metrology and Its Applications to Brake Squeal 329 J. D. Fieldhouse, A. Ettemeyer, and F. Chen CHAPTER 15 Squeal Reduction and Prevention 373 R. L. Quaglia and F. Chen Index 391 About the AuthorMECHANISMS AND CAUSES OF DISC BRAKE SQUEAL C. A. Tan
31、 and F. Chen CHAPTER 1 1.1 INTRODUCTION Brake squeal in general is caused by friction-induced, self-excited, and self-sustained vibra- tion in a short time via the rotating disc, and is often simply called self-excited vibration. A brake system may not become self-excited or lead to squeal until one
32、 or more of the mech- anisms that cause the frictional force to perform positive work on the system occur. Those mechanisms have presented challenging problems for researchers and engineers since the 1930s because of their complex nature, which involves multiple disciplines such as non- linear dynam
33、ics, contact mechanics, and tribology/nanotribology. The spatial and time scales of the problem, ranging from nano/microscopic to high frequency, further compli- cate the issues. Nevertheless, much progress has been made in gaining physical insight into the brake squeal phenomenon. However, disc bra
34、ke squeal remains a concern of the cus- tomers perception of quality and an elusory problem in the automotive industry, indicating that much work is still needed to further the understanding of brake squeal. This major- ity of this chapter is based on reference 1.1. We first briefly review various h
35、ypotheses on brake squeal mechanisms, followed by discussion of recent developments. Lastly, direc- tions for future research are outlined. 1.2 SQUEAL MECHANISMS AND CAUSES As described in some recent review articles 1.21.10, hypotheses on brake squeal mecha- nisms can be grouped into five major cat
36、egories or their combinations; reference 1.10 pro- vides the most comprehensive and detailed review. These categories are (1) stick-slip (the difference between static and kinetic friction coefficients), (2) negative damping (negative slope of the friction coefficient with respect to sliding speed),
37、 (3) geometric/kinematics (GK) constraint (sprag-slip, constant friction coefficient), (4) modal coupling (flutter- type instability) or mode lock-in, and (5) “hammering“ excitation (vibration induced by 12 CHAPTER 1 Mechanisms and Causes of Disc Brake Squeal uneven rotor surface variation during di
38、sc rotation). In the earlier stage of research, at- tempts were made to associate the brake squeal phenomenon with one of the above mech- anisms in order to determine the root cause. As more test evidence and analysis results become available, it seems quite obvious that none of the above mechanisms
39、 alone can provide a complete explanation of the squeal phenomenon. In some cases, negative damp- ing may seem more proper, but in others, modal coupling may be a better explanation. Indeed, which mechanism is the dominant one depends on both the brake system char- acteristics and the operational co
40、nditions. Reference 1.11 provides practical examples of contradictions or exceptions to some of the mechanisms listed above. That work also sug- gested a “hammering“ mechanism from an excitation viewpoint. It is well accepted from a dynamics viewpoint that squeal is caused by brake system instabilit
41、y. Thus, for a brake system that tends to become unstable as a result of its system characteristics, when one or more proper excitation mechanisms are present, the brake may generate squeal. From a vibration energy standpoint, as long as there is a mechanism to accumulate sufficient vi- bration ener
42、gy in a short time, the brake may squeal. A brake system may be highly prone to becoming unstable at certain frequencies because of the presence of certain types of excitation/triggering/perturbation. However, squeal may not occur in the field if no proper excitations are present at those frequencie
43、s during operation. On the other hand, even if a brake system is relatively stable at a certain frequency, squeal may still occur at this frequency if there is a very strong excitation at this frequency in the operating condi- tion. We shall discuss the squeal mechanisms in terms of the following as
44、pects: triggering mechanisms (excitation source), modal coupling/lock-in mechanisms (system inherent characteristics), and noise radiation mechanisms (system response). 1.2.1 Friction-Induced Periodic Impulsive Excitation Mechanism Stick-slip-induced frictional force variations and system instabilit
45、y were observed and studied by early researchers to explain brake squeal phenomena. The cause of the stick- slip is due primarily to the difference between the static and kinetic/dynamic coefficients of friction, the so-called Stribeck effect. It is noted that this difference may vary with time, dep
46、ending on the operating conditions, such as due to changes in contact areas, temperature variations, sliding speed fluctuations, and/or other conditions. The most classic example that describes stick-slip is to assume the brake pad as a rigid body that rests on a rotating disc (rotor) with a constan
47、t speed, to greatly simplify the problem. This can be modeled as a mass resting on a translating belt, with the mass con- necting to a linear spring at a fixed end, simulating the fixed end of a brake caliper/anchor bracket system. Initially, the spring force is smaller than the static friction forc
48、e so that the mass moves together with the rotating belt. As the deformation of the spring increases, the spring force increases to a value that equals or is larger than the static friction force, and the mass starts to slide (relative to the belt). As the mass slides, the motion is now gov- erned b
49、y the dynamic friction force (which is smaller than the static friction force), and the deformation of the spring and the spring force decrease. This causes the mass to gradually cease sliding, and the above cycle repeats to generate the stick-slip/slide phenomenon. Another example is to model the pad excited by a sinusoidal force. Figure 1-1 shows a schematic description of the simulation. The velocity of the pad and the excitation force are plotted in Fig. 1-2, in which slip/slide and stick regimes in the velocity are observed due to variations in the friction
