Materials for Automobile Bodies Geoffrey Davies AMSTERDAM • BOSTON • HEIDELBERG • LONDON NEW YORK • OXFORD • PARIS • SAN DIEGO SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO Butterworth-Heinemann is an imprint of Elsevier Butterworth-Heinemann is an imprint of Elsevier The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, UK 225 Wyman Street, Waltham, MA 02451, USA First edition 2012 Copyright Ó 2012 Elsevier Ltd. All rights reserved No part of this publication 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 prior written permission of the publisher Permissions may be sought directly from Elsevier’s Science & Technology Rights Department in Oxford, UK: phone (+44) (0) 1865 843830; fax (+44) (0) 1865 853333; email: permissions@elsevier. 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Because of rapid advances in the medical sciences, in particular, independent verification of diagnoses and drug dosages should be made British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is availabe from the Library of Congress ISBN: 978-0-08-096979-4 For information on all Butterworth-Heinemann publications visit our web site at books.com Printed and bound in Great Britain 12 13 14 15 16 10 9 8 7 6 5 4 3 2 1 Contents Acknowledgements xi CHAPTER 1 Introduction 1 1.2 Overview of content 3 1.4 General format of presentation 10 1.5 Introduction to body architecture and terminology 13 References 15 CHAPTER 2 Design and material utilization 17 Objective 18 Content 18 2.2 Historical perspective and evolving materials technology 19 2.1 Body zones and terminology 20 2.2 Distinction between body-on-chassis and unitary architecture 20 2.3 Early materials and subsequent changes 20 2.3 Finite element analysis 28 2.1 Materials for Autobodies 28 2.4 One manufacturer’s approach to current design 33 2.3 Design for static stiffness 34 2.5 Weight efficiency 36 2.5 Panel dent resistance and stiffness testing 42 2.1 Designing against fatigue 46 2.7 Alternative body architecture 48 2.1 The unitary aluminum body 48 2.2 The pressed spaceframe (or base unit) concept e steel 49 2.3 Pressed aluminum spaceframes and associated designs 53 2.4 The ASF aluminum spaceframe utilizing castings and profiles 56 2.5 Examples of hybrid material designs 62 2.6 Designs based on carbon fiber or CFRP 64 2.7 Magnesium 74 v vi Contents 2.8 Integration of materials into designs 74 2.2 Other materials used in body design 75 2.9 Engineering requirements for plastic and composite components 84 2.10 Cost analysis 85 Learning points 90 References 90 CHAPTER 3 Materials for consideration and use in automotive body structures 93 Objective 94 Content 94 3.2 Material candidates and selection criteria 98 3.1 Consistency: a prime requirement 100 3.1 Steel reduction and finishing processes 103 3.3 Effects in processing 117 3.4 Higher strength steels 117 3.2 Alloys for use in body structures 129 3.6 Polymers and composites 133 3.4 Polymer and composite processing 135 3.5 Advanced composites for competition cars 137 3.7 Repair 139 Learning points 142 References 143 CHAPTER 4 The role of demonstration, concept and competition cars 145 Objective 146 Content 146 4.2 The ECV 3 and ASVT 147 4.3 Collaborative development programs 153 4.1 ULSAB and ULSAB 40 153 4.2 FreedomCAR program 155 Contents vii 4.4 SuperLIGHT-CAR project 161 4.5 RWTH Aachen University FRP reinforcement program 162 4.2 F1 car structures d why composites? 173 4.4 Extent of use 174 4.5 Duty d the survival cell structure 174 4.6 Rule conformity and weight 175 4.7 Structural efficiency 177 4.8 F1 d A good match for composites 177 4.14 Survival cell proving 182 4.15 Survival cell crush and penetration 182 4.16 Survival cell impact 183 4.17 Impact absorber design 184 4.7 Hypercars 187 Learning points 189 References 190 CHAPTER 5 Component manufacture 193 Objective 194 Content 194 5.1 Sheet metal pressworking 194 5.2 Sheet properties and test procedures 198 5.3 Effect of surface topography 203 5.4 Effect of zinc coatings 205 5.1 Simultaneous engineering approach to design with aluminum 216 5.2 Superplastic forming 225 viii Contents 5.3 Manufacture of components in magnesium 228 5.4 Production of polymer parts 231 5.1 CFRP for EV and the future 233 Learning points 237 References 238 CHAPTER 6 Component assembly: materials joining technology 241 Objective 241 Content 241 6.2 Single-sided spot welding 253 6.5 Friction stir welding 258 6.5 Mechanical fastening 263 Learning points 265 References 266 CHAPTER 7 Corrosion and protection of the automotive structure 269 Objective 270 Content 270 7.2 Relevant corrosion processes 271 7.1 Corrosion of aluminum and other non-ferrous body materials 273 7.2 Mechanism of paint degradation 274 7.3 Effective design principles 276 7.4 Materials used for protection of the body structure 278 7.1 Zinc-coated steels e types and use for automotive construction 278 7.2 Painting of the automotive body structure 289 7.3 Environmental improvements in the automotive paint process 292 7.4 Supplementary protective systems 293 Contents ix 7.5 Empirical vehicle and laboratory comparisons 295 7.6 Introduction to electrochemical methods 297 Learning points 304 References 306 CHAPTER 8 Environmental and safety considerations 309 Objective 309 Content 310 8.2 Effect of body mass and emissions control 311 8.3 Life-cycle analysis 317 8.4 Recycling and ELV considerations 325 8.1 The European recycling program 325 8.2 The manufacturer’s policy 331 8.1 Heavy metal restrictions 338 8.6 BIW design for safety 339 8.1 Euro NCAP frontal impact test 339 8.2 Euro NCAP car-to-car side impact test 342 8.3 Euro NCAP side-impact pole test 343 8.4 Euro NCAP pedestrian protection tests 344 8.5 Improving safety performance 345 8.6 Influence of materials 347 8.7 Formula 1 safety regulations 351 Learning points 354 References 355 CHAPTER 9 Future trends in automotive body materials 357 Objective 358 Content 358 9.1 Current utilization and vehicle demographics 360 9.2 The influence of geography 361 9.3 Geographic development of the industry 363 9.4 The Japanese influence 365 9.4 Factors influencing material change in the future 370 9.1 Influence of environmental controls 371 9.2 Emissions control and fuel systems 371 x Contents 9.3 Actual BIW material effects 373 9.4 Recycling and ELV legislation 375 9.5 Effects of future design and engineering trends 376 9.6 Advances in manufacturing technology 379 9.7 Improvements in materials specification e trends and requirements 381 9.5 Combined effect of factors on materials utilization within ‘expected’ and ‘accelerated’ timescales 387 9.1 Possible consequences regarding BIW materials 391 Learning points 394 References 395 Index 397 CHAPTER Introduction CHAPTER OUTLINE 1 1.2 Overview of content.4 General format of presentation .5 Introduction to body architecture and terminology.1 INTRODUCTION The core content of this edition is essentially the same as the first, but the oppor- tunity has now been taken to update the coverage of both materials and associated manufacturing advances and generally report on progress made during the last decade.
The latest legislative and environmental requirements are highlighted and the response of the industry in terms of design and processing are outlined. These include the progress made with regard to higher strength steels, the application of composites, aluminum and other lightweight materials. Advances in processing include the automation of composite outer panel production to a mass production stage, essential if composites are to reach volume models, and the increasing use of lasers in joining, which has been enabled by the increasing versatility of beam technology offered by innovative power sources and transmission modes, such as YAG systems. The emergence of electrical drive systems and their possible effects on body-in-white (BIW) design and materials choice is also considered, although it may be at least a decade before electric vehicle (EV) systems in various guises have a real presence in the market.
In the meantime the opportunity exists for the full potential of alternative steels and lightweight materials being developed through current programs to be realized. Significant additions to relevant chapters have been made on subjects such as the development of lightweight body materials in North America and lessons learned from the Far East with regard to the implementation of new steel grades. In particular, the contribution from the FreedomCAR Automotive Lightweighting Materials program, sponsored by the US Department of Energy, is discussed. This program illustrates the considerable investment in terms of resources and efforts being made into the research and development of lightweight materials.
A major thrust is being made there to reduce the cost of carbon fiber, so that it becomes Materials for Automobile Bodies.00001-3 1 Copyright Ó 2012 Elsevier Ltd. All rights reserved. 2 CHAPTER 1 Introduction a competitive option as a material choice for body structure, and practical recycling solutions are being explored. The increased application of non-ferrous body content is being studied, especially with regard to magnesium.
The EV influenced ‘Future Steel Vehicle’ project is also outlined; it looks at possible structures for small and larger cars from hybrid through to fuel cell modes and considers the modifi- cations necessary for battery and cell stacks. The importance of this work is its emphasis on volume production and the pragmatic changes required in order for newer materials to be handled in volume, and, thus, achieve worthwhile reductions in greenhouse and other harmful emissions. The opportunity is also taken to update readers on the latest targets for emissions, recycling and end-of-life vehicle (ELV) legislation and the recent progress that has been made by manufacturers in addressing them. A major objective for BIW development remains its contribution to emissions control through weight reduction, which is achieved by design and materials choice, and complements the work being carried out on alternative power modes.
Significant reductions have been achieved in current structures, but further reductions will be necessary to offset the heavier batteries or cell stacks of future designs. Steady progress is reported in the use of hydrogen, used either as a replacement fuel in conventional engines or within fuel cells, together with the different types of ‘electromobility’ referred to above. Events in the last decade have underlined the critical status of oil supplies. The strategic importance of oil has been highlighted by recent events in the Middle East, while in the Gulf of Mexico hurricane damage to significant oil installations and has further heightened our awareness of oil dependence.
Some reports suggest that existing reserves of oil could run out in 10 years, although 40 years is generally thought to be more realistic. Other events have emphasized the danger to the environment by mismanagement of these oil resources. The interest in alternative fuels is, therefore, intense. Hybrid electric vehicles (HEV) now have plug-in derivatives (PHEV); battery electric vehicles (BEV) have been developed as city cars, while small internal combustion engines (ICE) supplement electrical systems in extended range vehicles (EREV).
Fuel cell systems (FCEV) are now undergoing extended fleet trials. Serious programs are working on the provision of a universal infrastructure for the supply of hydrogen and plug-in fast-recharging stations for next generation electric vehicles. The effects of these systems and the differences in material requirements and architecture compared with ICE-propelled vehicles are considered. The current range of steels will continue to be used in the medium term, as safety issues are addressed with increasingly sophisticated front, side and rear end designs, together with aluminum and magnesium to maximize weight reduction.
The development of plastics and composites in body design is further prompted by their good performance in pedestrian impact situations, and this is driving the search for effective recycling solutions for these materials. The basic format and content of the book still stands as before, as does the sequence of the chapters, which offers the most logical form of presentation.