Table Of ContentEngineering Materials and Processes
Series Editor
Professor Brian Derby, Professor of Materials Science
Manchester Materials Science Centre, Grosvenor Street, Manchester, M1 7HS, UK
Other titles published in this series
Fusion Bonding of Polymer Composites
C. Ageorges and L. Ye
Composite Materials
D.D.L. Chung
Titanium
G. Lütjering and J.C. Williams
Corrosion of Metals
H. Kaesche
Corrosion and Protection
E. Bardal
Intelligent Macromolecules for Smart Devices
L. Dai
Microstructure of Steels and Cast Irons
M. Durand-Charre
Phase Diagrams and Heterogeneous Equilibria
B. Predel, M. Hoch and M. Pool
Computational Mechanics of Composite Materials
M. Kamiński
Gallium Nitride Processing for Electronics, Sensors and Spintronics
S.J. Pearton, C.R. Abernathy and F. Ren
Materials for Information Technology
E. Zschech, C. Whelan and T. Mikolajick
Fuel Cell Technology
N. Sammes
Casting: An Analytical Approach
A. Reikher and M.R. Barkhudarov
Computational Quantum Mechanics for Materials Engineers
L. Vitos
Peter R. Brewin • Olivier Coube • Pierre Doremus
and James H. Tweed
Editors
Modelling of Powder
Die Compaction
123
P.R. Brewin O. Coube, PhD
European Powder Metallurgy European Powder Metallurgy
Association (EPMA) Association (EPMA)
2nd Floor, Talbot House 2nd Floor, Talbot House
Market Street Market Street
Shrewsbury, SY1 1LG Shrewsbury, SY1 1LG
UK UK
P. Doremus, PhD J.H. Tweed, PhD
Laboratoire GPM2 AEA Technology
ENSPG Gemini Building
PO Box 46 Harwell, Didcot
Saint Martin d'Heres 38402 Oxfordshire, OX11 0QR
France UK
ISBN 978-1-84628-098-6 e-ISBN 978-1-84628-099-3
Engineering Materials and Processes ISSN 1619-0181
British Library Cataloguing in Publication Data
Modelling of powder die compaction. - (Engineering materials and processes)
1. Compacting 2. Compacting - Mathematical models
I. Brewin, Peter R.
620.4'3
ISBN-13: 9781846280986
Library of Congress Control Number: 2007932623
© 2008 Springer-Verlag London Limited
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Foreword
Die compaction of powders that develop green strength on compaction is the
absolutely dominating forming technology for powdered materials. Areas of
application are structural parts, hardmetal and ceramic indexable inserts,
pharmaceutical tablets, electrical contacts, filters, hard magnets, soft magnetic
composites, friction materials and many others. In particular, multi cross-sectional
net-shape geometries have been gaining importance continuously, because the
ability to deliver complex shapes with higher and higher productivity has
contributed to competitive advantages over alternative forming techniques. Since
the raw material usage is better than 90 % in die compaction, even in areas that
could be served by competing manufacturing technologies, die compaction of
powders is often the most economic solution. The industries applying this
technique have seen tremendous innovation especially in shape capability,
reproducibility and productivity over the last 15 years that has resulted in high
added value, astonishing growth rates and increased employment also in high
labour cost countries.
In order to stay successful in an environment of competing shaping
technologies, the manufacturers must also in the future improve every single
processing step, which implies to reduce the compaction press downtime caused by
tool-setting iterations or tool readjustments. This requires more sophisticated
production planning and quantitative predictions of tool and press deformation,
crack formation and prevention during compaction and ejection, density
development during compaction and final density distribution in the compact as
well as the high-density phenomenon of delaminations. The goal of modelling die-
compaction processes is, therefore, to get a very detailed picture of the powder
density distribution in the die cavity before, during and after finishing the
compaction stroke to provide the precise local stress distribution within the
compact and the tool together with the associated deformations as the key to
precise and crack-free parts.
Much progress has been made in this direction during recent years especially
through the work of the EPMA-coordinated and EU-supported Modnet and Dienet
groups. Modelling is on the brink of becoming a usable tool also in die compaction
of powders. Many details require further intensive development work, because the
vi Foreword
mechanical behaviour of compressible powders is more complex to deal with than
that of incompressible solids. This book is a record of our present knowledge and
the newest achievements in this field. It gives an overview of the present status and
views and shows the existing application possibilities of compaction modelling in
developing new tooling and optimising compaction sequences. Also, the remaining
deficiencies and areas of future progress are mentioned. The book resembles a
balance sheet of what compaction modelling is currently capable of performing for
designers and practitioners. It includes rich databases of information useful for
future work in the field. It is highly welcomed as the starting point to continue
ongoing developments for reliable and user-friendly widespread application.
Paul Beiss
RWTH Aachen
Acknowledgements
The editors would like to thank all those who contributed to the text of this book.
Additionally the editors would like to thank two individuals who originally laid the
foundation for the Thematic Networks, Dr David Whittaker of DW Associates and
Mr. Bernard Williams, former Executive Director, EPMA.
The editors would also like to thank all those who participated in the Thematic
Networks and the associated independently funded research projects, without
whose enthusiasm and involvement little would have been achieved.
Finally the editors would like to acknowledge the support of the European
Union for this work.
Peter Brewin
EPMA
Olivier Coube
EPMA
Pierre Doremus
Institut National Polytechnique de Grenoble
James Tweed
AEA Technology
Figure Acknowledgements
The editors acknowlege permission to publish illustrations that have previously
been published elsewhere. In particular, thanks are due to:
• AEA Technology for Figures 9.1, 9.2, 9.12, 9.13, 12.10 and 12.11. This
work was undertaken as part of the project on “Minimising density
vartiations in powder compacts” funded by the UK Department of Trade
and Industry.
• Elsevier Ltd for Figures 9.3, 9.14, 9.15, 14.1 and 14.9.
• EPMA for Figures 9.8-9.11, 11.4, 11.10, 12.2, 12.8, 12.12 and 12.13,
Appendix 2, figures on pages 299-307, 310-311and 315-317.
• John Wiley and Sons Ltd. for Figure 14.10.
Contents
Lists of Contributors and Project Partners......................................................xvii
1 Introduction.......................................................................................................1
P.Brewin, O.Coube, P.Doremus and J.H.Tweed
1.1 Treatment of Main Subjects in Compaction Modelling......................................2
1.2 Summaries of Individual Chapters.....................................................................2
2 Modelling and Part Manufacture....................................................................7
P.Brewin, O.Coube, J.A.Calero, H.Hodgson, R.Maassen and M.Satur
2.1 Introduction ........................................................................................................7
2.2. Requirements for Improving the PM Production Process.................................8
2.2.1 Introduction................................................................................................8
2.2.2 Selection of Powder Blends.....................................................................10
2.2.3 Tooling Design........................................................................................14
2.2.4 Press Selection.........................................................................................17
2.2.5 Production and Quality Control...............................................................18
2.2.6 Sintering and Infiltration..........................................................................18
2.3 Requirements for Compaction Modelling........................................................19
2.3.1 Input-Data Generation.............................................................................19
2.3.2 Modelling and Part Manufacture: Requirements
of the Hardmetal Industry (“HM”)..........................................................21
2.3.3 Modelling and Parts Manufacture: Requirements
of Ferrous Structural (“FS”) Parts Industry............................................24
2.3.4 Validation................................................................................................26
References…… ......................................................................................................28
xii Contents
3 Mechanics of Powder Compaction................................................................31
A.C.F.Cocks
3.1 Introduction ......................................................................................................31
3.2 Uniaxial Deformation.......................................................................................32
3.3 Deformation under Multiaxial States of Stress.................................................34
References........ ......................................................................................................41
4 Compaction Models........................................................................................43
A.C.F.Cocks, D.T.Gethin, H.-Å. Häggblad, T.Kraft and O.Coube
4.1 Micromechanical Compaction Models.............................................................43
4.1.1 Stage 0 Models........................................................................................44
4.1.2 Stage 1 Models........................................................................................46
4.1.3 Stage 2 Models........................................................................................54
4.2 Phenomenological Compaction Models...........................................................55
4.2.1 Introduction..............................................................................................55
4.2.2 Cap Model...............................................................................................57
4.2.3 Cam-Clay Model......................................................................................59
4.3 Closure…... ......................................................................................................62
References…… ......................................................................................................62
5 Model Input Data – Elastic Properties..........................................................65
M.D.Riera, J.M.Prado and P.Doremus
5.1 Introduction ......................................................................................................65
5.2 Elastic Model ..................................................................................................65
5.3 Experimental Techniques.................................................................................68
5.3.1 Characterisation of Elastic Properties of Green Compacted Samples.....68
5.3.2 Characterisation of Elastic Properties at High Stresses...........................73
5.4 Conclusions ......................................................................................................76
References…… ......................................................................................................76
6 Model Input Data – Plastic Properties..........................................................77
P.Doremus
6.1 Introduction ......................................................................................................77
6.2 Closed-Die Compaction Test............................................................................77
6.2.1 Discussion of Assumptions A1,A2,A3....................................................83
6.2.2 Influence of the Sample Aspect Ratio on Experimental Results..............85
6.3 Powder Characterisation from Triaxial Test.....................................................88
6.4 Concluding Comments.....................................................................................92
References…… ......................................................................................................93
7 Model Input Data – Failure...........................................................................95
P.Doremus
7.1 Introduction ......................................................................................................95
7.2 Tensile Test ......................................................................................................96
7.3 Diametral Compression Test.............................................................................98
7.4 Simple Compression Test...............................................................................100
