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Engineering Design for Wear Second Edition, Revised and Expanded Engineering Design for Wear Second Edition, Revised and Expanded Raymond G. Bayer Tribology Consultant Vestal, New York, U.S.A. MARCEL DEKKER, INC. NEW YORK · BASEL Copyright © 2004 Marcel Dekker, Inc. This edition is expanded and updated from a portion of the first edition, Mechanical Wear Prediction and Prevention (Marcel Dekker, 1994). The remaining material in the first edition has been expanded and updated for Mechanical Wear Fundamentals and Testing: Second Edition, Revised and Expanded (Marcel Dekker, 2004). Although great care has been taken to provide accurate and current information, neither the author(s) nor the publisher, nor anyone else associated with this publication, shall be liable for any loss, damage, or liability directly or indirectly caused or alleged to be caused by this book. The material contained herein is not intended to provide specific advice or recommendations for any specific situation. Trademark notice: Product or corporate names may be trademarks or registered trademarks and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress. ISBN: 0-8247-4772-0 This book is printed on acid-free paper. Headquarters Marcel Dekker, Inc., 270 Madison Avenue, New York, NY 10016, U.S.A. tel: 212-696-9000; fax: 212-685-4540 Distribution and Customer Service Marcel Dekker, Inc., Cimarron Road, Monticello, New York 12701, U.S.A. tel: 800-228-1160; fax: 845-796-1772 Eastern Hemisphere Distribution Marcel Dekker AG, Hutgasse 4, Postfach 812, CH-4001 Basel, Switzerland tel: 41-61-260-6300; fax: 41-61-260-6333 World Wide Web http://www.dekker.com The publisher offers discounts on this book when ordered in bulk quantities. For more infor- mation, write to Special Sales / Professional Marketing at the headquarters address above. Copyright © 2004 by Marcel Dekker, Inc. All Rights Reserved. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage and retrieval system, without permission in writing from the publisher. Current printing (last digit): 10 9 8 7 6 5 4 3 2 1 PRINTED IN THE UNITED STATES OF AMERICA Copyright © 2004 Marcel Dekker, Inc. To my wife, Barbara Copyright © 2004 Marcel Dekker, Inc. Preface It has been a decade since the first edition of this book was published. During that period important changes in the field of tribology have occurred. As a consultant I have also gained additional tribological experience in a wide range of industrial applications. It was thus decided to develop a second edition with the goal of incorporating this new informa- tion and additional experience into a more useful and current book, as well as clarifying and enhancing the original material. The purpose and perspectives of the first edition were to be maintained, namely, “to provide a general understanding . for the practicing engi- neer and designer [and an] engineering perspective . .”. As rewriting progressed it became clear that the greatly expanded text would develop into a much larger volume than the first. We therefore decided to divide the material into two volumes, while keeping the basic format and style. Essentially the first two parts of the original edition on the funda- mentals of wear and wear testing are combined into a single volume, Mechanical Wear Fundamentals and Testing (Marcel Dekker, 2004). The remaining two parts of the first edition, which focus on design approaches to wear and the resolution of wear problems, are the basis for this second volume, Engineering Design for Wear. While a good deal of background material is the same as in the first edition, sig- nificant changes have been made. The most pervasive is the use of a new way of clas- sifying wear mechanisms, which I have found to be useful in formulating approaches to industrial wear situations. As a result, Part A, Fundamentals, has been reorganized and rewritten to accommodate this new classification and to include additional materi- al on wear mechanisms. Additional wear tests are described in Part B, Testing, which has been expanded to include friction tests. These first two parts are discussed in Mechanical Wear Fundamentals and Testing. Part A, Design, of Engineering Design for Wear has been modified by expanding several sections, as well as adding a section on a design methodology, design triage, that has been found to be useful. Among the expanded treatments is the consideration of material aspects and the treatment of rolling bearing wear and rolling wear, as well as impact wear. An additional case study has been added to the Problem Solving section, Part B, which illustrates the use of ana- lytical modeling for resolving wear problems. Additional appendixes have been added, providing further information for use in engineering situations. These additional appendixes include tables on threshold stress for galling and sliding wear relationships for different contact situations. A glossary of wear mechanisms has also been added. This book demonstrates the feasibility of designing for wear and using analytical approaches to describe wear in engineering situations, based on my experience over the last 40 years. Raymond G. Bayer v Copyright © 2004 Marcel Dekker, Inc. Contents Preface v 1 Design Perspective of Wear Behavior1 1.1 Introduction 1 1.2 System Nature of Wear 2 1.3 Basic Mechanisms of Wear 3 1.4 Mild and Severe Wear Behavior 5 1.5 Operational Categories of Tribosystems 5 1.6 Two-Body Tribosystems 6 1.7 One-Body Tribosystems 17 1.8 Materials and Wear Behavior 17 2 Engineering Models forWear 45 2.1 Introduction 45 2.2 Wear and Wear Rate Relationships for Sliding Wear 49 2.3 Wear and Wear Rate Relationships for Abrasive Wear 55 2.4 Zero Wear and Measurable Wear Models for Sliding 56 2.5 Percussive Impact Wear Models 75 2.6 Model for Rolling Wear 89 2.7 Model for Ball and Roller Bearing Wear 96 2.8 Models for Journal Bearing Wear 104 2.9 Models for Erosive Wear 123 2.10 Models for Tool Wear 127 3 Wear Design 137 3.1 General 137 3.2 System Analysis 140 vii Copyright © 2004 Marcel Dekker, Inc. viii Contents 3.3 Model Selection and Development 142 3.4 Database Identification and Development 147 3.5 Verification 147 3.6 Design Triage 148 4 Design Guidelines 151 4.1 Introduction 151 4.2 Guidelines 151 4.2.1 Reliance on Analytical Design Methods Increases the Degree of Conservatism Required 151 4.2.2 Wear is a System Property; Utilize All Design Parameters That Can Influence Wear 151 4.2.3 Approach Extrapolation of Data and Extension of Designs Cautiously 152 4.2.4 Design with Limits and Characteristics of Materials in Mind 152 4.2.5 Metals and Polymers Tend to Require Different Designs152 4.2.6 Design So That a Mild Wear Condition Exists 153 4.2.7 AMinimum Requirement for Material Selection is That the Material Should be Stable in the Operating Environment153 4.2.8 While Fluid or EHD Lubrication is very Effective for Reducing Wear, Specific Designs are Required to Insure this Form of Lubrication 153 4.2.9 Minimize Exposure to Abrasive Particles 154 4.2.10 In Abrasive Situations Make the Wear Surfaces Harder than the Abrasives 154 4.2.11 Optimize Contact Geometry to Minimize Stresses154 4.2.12 Use a Lubricant Whenever Possible 155 4.2.13 Use Dissimilar Materials 155 4.2.14 Increasing Hardness Tends to Reduce Wear 155 4.2.15 To Increase System Life (Reduce System Wear), It is Sometimes Necessary to Increase the Hardness of Both Members 155 4.2.16 Rolling is Preferred Over Sliding 155 4.2.17 Sliding or Fretting Motions Should be Eliminated in Impact Wear Situations 156 Copyright © 2004 Marcel Dekker, Inc. Contents ix 4.2.18 Compound Impact Situations Can Often be Treated as a Sliding Wear Situation in Which the Loads (Stresses) are Determined by the Impact 156 4.2.19 Impacts Should be Avoided in Sliding and Rolling Contacts 156 4.2.20 Elastomers Frequently Outperform Harder Materials and Reduce Counterface Wear in Impact Situations 156 4.2.21 Thicknesses of Conventional Coatings Generally Should be Greater than 100 µm 156 4.2.22 Use Moderate Surface Roughnesses 157 4.2.23 Avoid the Use of Stainless Steel Shafting with Impregnated Sintered Bronze Bearings 157 4.2.24 When Molded Filled Plastics Tend to Exhibit Significantly Different Initial and Long-Term Wear Behavior 157 4.2.25 When Glass or Other Hard Fillers are Used, the Hardness of the Counterface Should be Equal to or Greater than that of the Filler 157 4.2.26 The Tendency for Galling to Occur can be Reduced by Using Dissimilar and Hard Materials of Low Ductility, Lubrication, and Rougher Surfaces 158 4.2.27 Avoid the Use of Designs in Which Fretting Motions Can Occur 158 4.2.28 When Fretting Motions are Present, Design to Optimize Sliding Wear Life and to Minimize Abrasive Wear 158 4.2.29 Sacrificial Wear Design Should be Considered an Option When Satisfactory Life Cannot be Achieved with Available Materials 158 4.2.30 Conform to Vendor Recommendations Regarding Optimum Wear Performance 159 4.2.31 Changes Associated with Design Modifications or New Applications Should be Reviewed Carefully with Respect to their Potential Effect on Wear Behavior 159 4.2.32 Provide Adequate Clearance in Journal Bearings 159 4.2.33 The Severity of the Wear (Wear Rate) in Rolling, Sliding, and Impact Wear Situations can Generally be Correlated to the Ratio of Operating Stress Over Yield Stress (Stress Ratio) 159 4.2.34 Design so that Severe Wear Mechanisms Associated with Adhesion and Single-Cycle Deformation do not Occur 160 5 Design Examples 161 5.1 Introduction 161 5.2 Printer Cartridge 161 Copyright © 2004 Marcel Dekker, Inc.
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