Sheet Metal Forming FUNDAMENTALS Edited by Taylan Altan and A. Erman Tekkaya Materials Park, Ohio 44073-0002
Copyright 2012 by All rights reserved No part of this book may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the written permission of the copyright owner. First printing, August 2012 Great care is taken in the compilation and production of this book, but it should be made clear that NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING, WITHOUT LIMITATION, WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, ARE GIVEN IN CONNECTION WITH THIS PUBLICATION. Although this information is believed to be accurate by ASM, ASM cannot guarantee that favorable results will be obtained from the use of this publication alone. This publication is intended for use by persons having technical skill, at their sole discretion and risk. Since the conditions of product or material use are outside of ASM s control, ASM assumes no liability or obligation in connection with any use of this information. No claim of any kind, whether as to products or information in this publication, and whether or not based on negligence, shall be greater in amount than the purchase price of this product or publication in respect of which damages are claimed. THE REMEDY HEREBY PROVIDED SHALL BE THE EXCLUSIVE AND SOLE REMEDY OF BUYER, AND IN NO EVENT SHALL EITHER PARTY BE LIABLE FOR SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES WHETHER OR NOT CAUSED BY OR RESULTING FROM THE NEGLIGENCE OF SUCH PARTY. As with any material, evaluation of the material under end-use conditions prior to specification is essential. Therefore, specific testing under actual conditions is recommended. Nothing contained in this book shall be construed as a grant of any right of manufacture, sale, use, or reproduction, in connection with any method, process, apparatus, product, composition, or system, whether or not covered by letters patent, copyright, or trademark, and nothing contained in this book shall be construed as a defense against any alleged infringement of letters patent, copyright, or trademark, or as a defense against liability for such infringement. Comments, criticisms, and suggestions are invited, and should be forwarded to ASM International. Prepared under the direction of the ASM International Technical Book Committee (2011 2012), Bradley J. Diak, Chair. ASM International staff who worked on this project include Scott Henry, Senior Manager, Content Development and Publishing; Karen Marken, Senior Managing Editor; Steven L. Lampman, Content Developer; Sue Sellers, Editorial Assistant; Bonnie Sanders, Manager of Production; Madrid Tramble, Senior Production Coordinator; and Diane Whitelaw, Production Coordinator. Library of Congress Control Number: 2011945709 ISBN-13: 978-1-61503-842-8 ISBN-10: 0-61503-842-6 SAN: 204-7586 Materials Park, OH 44073-0002 Printed in the United States of America
Sheet Metal Forming Fundamentals Copyright 2012 T. Altan and A.E. Tekkaya, editors All rights reserved Contents Preface... vii Abbreviations and Symbols... ix Chapter 1 Metal Forming Processes in Manufacturing... 1 1.1 Classification of Manufacturing Processes... 1 1.2 Characteristics of Manufacturing Processes... 1 1.3 Metal Forming Processes in Manufacturing... 2 1.4 Classification of Metal Forming Processes... 3 Chapter 2 Classification and Description of Sheet Metal Forming Operations... 5 2.1 Process Variables... 5 2.2 Sheet Metal Forming as a System... 6 2.3 Classification of Geometries... 10 2.4 Bending and Flanging... 11 2.5 Blank Preparation... 14 2.6 Deep Drawing... 15 2.7 Stretch Forming... 18 2.8 Incremental Forming... 22 2.9 Hybrid Forming Processes... 23 Chapter 3 Plastic Deformation Strain and Strain Rate... 27 3.1 Homogeneous or Uniform Deformation... 27 3.2 Volume Constancy during Plastic Deformation... 29 3.3 Infinitesimal True Strains and Strain Rates... 29 3.4 Principal Strains and Strain Paths... 31 3.5 Equivalent Strain Rate and Equivalent Strain... 32 Chapter 4 Plastic Deformation Flow Stress, Anisotropy, and Formability... 33 4.1 Tensile Test... 33 4.2 Flow Stress Curves... 37 4.3 Methods to Determine Flow Stress of Sheet Materials... 39 4.4 Formability... 44 4.5 Forming Limit Curves (FLCs)... 48 iii
iv / Contents Chapter 5 Plastic Deformation State of Stress, Yield Criteria Flow Rule, and Hardening Rules... 53 5.1 General State of Stress... 53 5.2 Principal Stresses... 54 5.3 Volumetric Stress or Hydrostatic Pressure... 54 5.4 Deviatoric Stress... 55 5.5 Isotropic Yield Criteria (Flow Criteria)... 56 5.6 Tresca Yield Criterion... 56 5.7 Von Mises Yield Criterion... 57 5.8 Comparison of Tresca and von Mises Criteria... 58 5.9 Anisotropic Yield Criteria... 58 5.10 Flow Rules... 63 5.11 Power and Energy of Deformation... 64 5.12 Effective Strain and Effective Strain Rate... 65 5.13 Hardening Laws... 66 Chapter 6 Materials for Sheet Forming... 73 6.1 Low-Carbon Sheet Steels... 73 6.2 Coated Sheet Steels... 78 6.3 Stainless Steels... 79 6.4 Aluminum Alloys... 82 6.5 Magnesium Alloys... 86 Chapter 7 Friction and Lubrication... 89 7.1 Lubrication Mechanisms and Friction Laws... 89 7.2 Lubricants for Sheet Metal Forming... 91 7.3 Tribological Tests for Evaluation of Lubricants in Sheet Metal Forming... 94 7.4 Tribological Tests for Warm and Hot Stamping... 98 7.5 Tribological Tests for Punching and Blanking... 100 Chapter 8 Deep Drawing of Round and Rectangular Cups... 105 8.1 Deformation during Deep Drawing... 105 8.2 Deep Drawing of Rectangular Cups... 121 8.3 Prediction of Punch Force and BHF Case Study... 123 Chapter 9 Principles of Sheet Forming Presses... 129 9.1 Components of Presses... 129 9.2 Characteristics of Presses... 131 9.3 Quick Die Change Systems... 139 Chapter 10 Mechanical Presses... 145 10.1 Mechanical Press Designs... 145 10.2 Characteristics of Mechanical Presses... 150 10.3 Other Features of Mechanical Presses... 155 Chapter 11 Electromechanical Servo-Drive Presses... 161 11.1 Servo-Press Drives Versus Conventional Press Drives... 161 11.2 Servo-Press Drives... 163
Contents / v 11.3 Applications... 167 11.4 Cushions/Die Cushions... 173 11.5 Comparison of Mechanical and Servo Presses... 174 11.6 New Process Development Using Servo-Press Characteristics... 176 11.7 Summary... 178 Chapter 12 Hydraulic Presses... 181 12.1 Components of Hydraulic Presses... 182 12.2 Drive Systems... 188 12.3 Characteristics of Hydraulic Presses... 190 12.4 Hydraulic Press Designs... 196 Chapter 13 Cushion Systems for Sheet Metal Forming... 203 13.1 Blank holder Systems in Double-Action Presses... 203 13.2 Single-Action Presses with Cushion System... 206 13.3 Multipoint Cushion (MPC) Systems... 211 Appendix A Flow Stress Curves... 221 Appendix B Glossary... 233 Index... 267