Metal Foams: A Design Guide docx

Metal Foams: A Design Guide Metal Foams: A Design Guide M.F. Ashby, A.G. Evans, N.A. Fleck, L.J. Gibson, J.W. Hutchinson and H.N.G. Wadley BOSTON OXFORD AUCKLAND JOHANNESBURG MELBOURNE NEW DELHI Copyright  2000 by Butterworth-Heinemann All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or trans- mitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of a publisher. Recognizing the importance of preserving what has been written, Butterworth-Heinemann prints its books on acid-free paper whenever possible. Butterworth-Heinemann supports the efforts of American Forests and the Global ReLeaf program in its campaign for the betterment of trees, forests, and our environment. Library of Congress Cataloguing-in-Publication Data A catalogue record for this book is available from the Library of Congress. 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For information, please contact: Manager of Special Sales Butterworth-Heinemann 225 Wildwood Avenue Woburn, MA 01801-2041 Tel: 781-904-2500 Fax: 781-904-2620 For information on all Butterworth-Heinemann publications available, contact our World Wide Web home page at: http://www.bh.com 10 987654 321 Typeset by Laser Words, Madras, India Printed in the United States of America Contents Preface and acknowledgements ix List of contributors xi Table of physical constants and conversion units xiii 1 Introduction 1 1.1 This Design Guide 1 1.2 Potential applications for metal foams 3 1.3 The literature on metal foams 5 2 Making metal foams 6 2.1 Making metal foams 6 2.2 Melt gas injection (air bubbling) 8 2.3 Gas-releasing particle decomposition in the melt 9 2.4 Gas-releasing particle decomposition in semi-solids 11 2.5 Casting using a polymer or wax precursor as template 11 2.6 Metal decomposition on cellular preforms 14 2.7 Entrapped gas expansion 14 2.8 Hollow sphere structures 16 2.9 Co-compaction or casting of two materials, one leachable 19 2.10 Gas–metal eutectic solidification 20 2.11 Literature on the manufacture of metal foams 20 3 Characterization methods 24 3.1 Structural characterization 24 3.2 Surface preparation and sample size 26 3.3 Uniaxial compression testing 27 3.4 Uniaxial tension testing 29 3.5 Shear testing 30 3.6 Multi-axial testing of metal foams 31 3.7 Fatigue testing 34 3.8 Creep testing 35 3.9 Indentation and hardness testing 35 3.10 Surface strain mapping 36 3.11 Literature on testing of metal foams 38 4 Properties of metal foams 40 4.1 Foam structure 40 4.2 Foam properties: an overview 42 vi Contents 4.3 Foam property charts 48 4.4 Scaling relations 52 References 54 5 Design analysis for material selection 55 5.1 Background 55 5.2 Formulating a property profile 56 5.3 Two examples of single-objective optimization 58 5.4 Where might metal foams excel? 61 References 61 6 Design formulae for simple structures 62 6.1 Constitutive equations for mechanical response 62 6.2 Moments of sections 64 6.3 Elastic deflection of beams and panels 67 6.4 Failure of beams and panels 69 6.5 Buckling of columns, panels and shells 70 6.6 Torsion of shafts 72 6.7 Contact stresses 74 6.8 Vibrating beams, tubes and disks 76 6.9 Creep 78 References 79 7 A constitutive model for metal foams 80 7.1 Review of yield behavior of fully dense metals 80 7.2 Yield behavior of metallic foams 82 7.3 Postscript 86 References 87 8 Design for fatigue with metal foams 88 8.1 Definition of fatigue terms 88 8.2 Fatigue phenomena in metal foams 90 8.3 S– N data for metal foams 94 8.4 Notch sensitivity in static and fatigue loading 97 References 101 9 Design for creep with metal foams 103 9.1 Introduction: the creep of solid metals 103 9.2 Creep of metallic foams 105 9.3 Models for the steady-state creep of foams 106 9.4 Creep data for metallic foams 107 9.5 Creep under multi-axial stresses 109 9.6 Creep of sandwich beams with metal foam cores 109 References 112 10 Sandwich structures 113 10.1 The stiffness of sandwich beams 113 10.2 The strength of sandwich beams 116 10.3 Collapse mechanism maps for sandwich panels 120 10.4 Case study: the three-point bending of a sandwich panel 123 Contents vii 10.5 Weight-efficient structures 124 10.6 Illustration for uniformly loaded panel 126 10.7 Stiffness-limited designs 133 10.8 Strength-limited designs 140 10.9 Recommendations for sandwich design 148 References 148 11 Energy management: packaging and blast protection 150 11.1 Introduction: packaging 150 11.2 Selecting foams for packaging 151 11.3 Comparison of metal foams with tubular energy absorbers 157 11.4 Effect of strain rate on plateau stress 161 11.5 Propagation of shock waves in metal foams 163 11.6 Blast and projectile protection 166 References 169 12 Sound absorption and vibration suppression 171 12.1 Background: sound absorption in structural materials 171 12.2 Sound absorption in metal foams 173 12.3 Suppression of vibration and resonance 175 References 179 13 Thermal management and heat transfer 181 13.1 Introduction 181 13.2 Heat transfer coefficient 182 13.3 Heat fluxes 184 13.4 Pressure drop 186 13.5 Trade-off between heat transfer and pressure drop 187 References 188 14 Electrical properties of metal foams 189 14.1 Measuring electrical conductivity or resistivity 189 14.2 Data for electrical resistivity of metal foams 190 14.3 Electrical conductivity and relative density 191 References 193 15 Cutting, finishing and joining 194 15.1 Cutting of metal foams 194 15.2 Finishing of metal foams 194 15.3 Joining of metal foams 195 References 199 16 Cost estimation and viability 200 16.1 Introduction: viability 200 16.2 Technical modeling and performance metrics 201 16.3 Cost modeling 202 16.4 Value modeling 206 16.5 Applications 212 References 216 viii Contents 17 Case studies 217 17.1 Aluminum foam car body structures 217 17.2 Integrally molded foam parts 219 17.3 Motorway sound insulation 220 17.4 Optical systems for space applications 222 17.5 Fluid–fluid heat exchangers 224 17.6 Lightweight conformal pressure tanks 225 17.7 Electrodes for batteries 225 17.8 Integrated gate bipolar transistors (IGBTs) for motor drives 226 17.9 Applications under consideration 232 18 Suppliers of metal foams 234 19 Web sites 239 Appendix: Catalogue of material indices 242 Index 247 Preface and acknowledgements Metal foams are a new class of materials with low densities and novel physical, mechanical, thermal, electrical and acoustic properties. This Design Guide is a contribution to the concurrent development of their science and exploitation. It seeks to document design information for metal foams even as the scientific research and process development are evolving. This should help to identify promising industrial sectors for applications, guide process development and accelerate take-up. This work is supported by the DARPA/ONR MURI Program through Grant No. N00014-1-96-1028 for Ultralight Metal Structures and by the British Engineering and Science Research Council through a Research Grant. Many individuals and groups have contributed to its contents. They include Professor B. Budiansky, Professor H. Stone, Professor R. Miller, Dr A. Bastawros, Dr Y. Sugimura of the Division of Engineering and Applied Sciences, Harvard University; Dr T.J. Lu, Dr Anne-Marie Harte, Dr V. Deshpande of the Micromechanics Centre, Engineering Department, Cambridge University; Dr E.W. Andrews and Dr L. Crews of the Department of Materials Science and Engineering, MIT; Professor D. Elzey, Dr D. Sypeck and Dr K. Dharmasena of the Department of Materials Science and Engineering, UVA; Dr John Banhart of the Fraunhofer Instit ¨ ut Angewandte Materialsforschung, Bremen; Professor H.P. Degisher and Dr Brigdt Kriszt of the Technical University of Vienna, Dr Jeff Wood of Cymat Corp. Mississauga, Canada; and Mr Bryan Leyda of Energy Research and Generation Inc. Oakland, CA. Although the compilers of this Guide have made every effort to confirm the validity of the data and design information it contains, the compilers make no warranty, either expressed or implied, with respect to their quality, accuracy or validity. List of contributors M.F. Ashby Cambridge Centre for Micromechanics Engineering Department University of Cambridge Cambridge CB2 1PZ UK mfa2@eng.cam.ac.uk A.G. Evans Princeton Materials Institute Bowen Hall 70 Prospect Avenue Princeton, NJ 08540 USA anevans@princeton.edu N.A. Fleck Cambridge Centre for Micromechanics Engineering Department University of Cambridge Cambridge CB2 1PZ UK naf1@eng.cam.ac.uk L.J. Gibson Department of Materials Science and Engineering Massachusetts Institute of Technology Cambridge, MA 02139 USA ljgibson@mit.edu J.W. Hutchinson Division of Engineering and Applied Sciences Harvard University xii List of contributors Oxford Street Cambridge, MA 02138 USA Hutchinson@mems.harvard.edu H.N.G. Wadley Department of Materials Science and Engineering School of Engineering and Applied Science University of Virginia Charlottesville, VA 22903 USA haydn@virginia.edu [...]... page 4 Metal Foams: A Design Guide Application Comment Sandwich cores Metal foams have low density with good shear and fracture strength – see Chapters 7 and 10 Strain isolation Metal foams can take up strain mismatch by crushing at controled pressure – see Chapters 7 and 11 Mechanical damping The damping capacity of metal foams is larger than that of solid metals by up to a factor of 10 – see Chapter... properties, and applications Journal of Materials Science 18 1899–1911 Banhart, J and Baumeister, J (1988) Production methods for metallic foams In Shwartz, D.S., Shih, D.S., Evans, A. G and Wadley, H.N.G (eds) (1998) Porous and Cellular Materials for Structural Application, Materials Research Society Proceedings, Vol 521, MRS, Warrendale, PA, USA Making metal foams a) Metal - Hydrogen binary phase diagram... 4 Vibration control Foamed panels have higher natural flexural vibration frequencies than solid sheet of the same mass per unit area – see Chapter 4 Acoustic absorption Reticulated metal foams have sound-absorbing capacity – see Chapter 12 Energy management: compact or light energy absorbers Metal foams have exceptional ability to absorb energy at almost constant pressure – see Chapter 11 Packaging... materials manufactured by this route are costly Though GASAR materials were among the first highly porous materials to attract significant interest, they remain confined to the laboratory and are not yet commercially available 2.11 Literature on the manufacture of metal foams General Astro Met, Inc Ampormat Porous Materials, Astro Met, Inc., Cinncinnati Davies, G.J and Zhen, S (1983) Metallic foams: their... deepdrawn to shape and placed in a furnace to expand the core, giving a shaped, metal- foam cored sandwich-panel Only foamed aluminum is commercially available today, but other alloy foams are being developed using different foaming agents 2.5 Casting using a polymer or wax precursor as template Open-cell polymer foams with low relative densities and a wide range of cell sizes of great uniformity are available... commercially available metal foams are based on aluminum or nickel Methods exist for foaming magnesium, lead, zinc, copper, bronze, titanium, steel and even gold, available on custom order Given the intensity of research and process development, it is anticipated that the range of available foams will expand quickly over the next five years 1.1 This Design Guide Metallic foams (‘metfoams’) are a new class... of metal foams in energy, acoustic and thermal management Chapter 14 describes how they can be cut, finished and joined Chapter 15 discusses economic aspects of metal foams and the way economic and technical assessment are combined to establish viability Chapter 16 reports case studies illustrating successful and potential applications of metal foams Chapter 17 contains a list of the suppliers of metal. .. high-temperature capability Ability to absorb impact at constant load, coupled with thermal stability above room temperature – see Chapter 11 Artificial wood Metal foams have some wood-like characteristics: (furniture, wall panels) light, stiff, and ability to be joined with wood screws – see Chapter 14 Thermal management: Open-cell foams have large accessible surface area and high cell-wall conduction... oxide layers on gas-generating hydride particles during production of aluminum foams In Shwartz, D.S., Shih, D.S., Evans, A. G and Wadley, H.N.G (eds) Porous and Cellular Materials for Structural Application, Materials Research Society Proceedings, Vol 521, MRS, Warrendale, PA, USA Miyoshi, T., Itoh, M., Akiyama, S and Kitahara, A (1998) Aluminum foam, ALPORAS, the production process, properties and applications,... process, a bed of particles of the leachable material is infiltrated by liquid metal under pressure, and allowed to cool Leaching of the particles again gives a cellular metallic structure of great uniformity 2.10 Gas metal eutectic solidification Numerous metal alloy–hydrogen binary phase diagrams exhibit a eutectic; these include Al-, Be-, Cr-, Cu-, Fe-, Mg-, Mn- and Ni-based alloys The alloys are melted, . Metal Foams: A Design Guide Metal Foams: A Design Guide M.F. Ashby, A. G. Evans, N .A. Fleck, L.J. Gibson, J.W. Hutchinson and H.N.G. Wadley BOSTON OXFORD AUCKLAND JOHANNESBURG MELBOURNE. This Design Guide 1 1.2 Potential applications for metal foams 3 1.3 The literature on metal foams 5 2 Making metal foams 6 2.1 Making metal foams 6 2.2 Melt gas injection (air bubbling) 8 2.3 Gas-releasing. see Chapters 7 and 11 Mechanical damping The damping capacity of metal foams is larger than that of solid metals by up to a factor of 10 – see Chapter 4 Vibration control Foamed panels have