Cette publication ne fait pas partie de la bibliothèque YouScribe
Elle est disponible uniquement à l'achat (la librairie de YouScribe)
Achetez pour : 189,89 € Lire un extrait

Téléchargement

Format(s) : PDF

avec DRM

Modelling of Powder Die Compaction

De
0 page

Manufacture of components from powders frequently requires a compaction step. This is widely used in the powder metallurgy, ceramic, hardmetal, magnet, pharmaceutical, refractory and other sectors to make anything from complex gears for cars to pills to dishwasher tablets. Development of the tooling to manufacture a component can be a long process with several iterations. A complementary approach is to use a model of the compaction process to predict the way that powder behaves during compaction and hence the loads that need to be applied to achieve compaction and the quality of the compacted part.


Modelling of the process of die compaction has been the subject of recent collaborative research from leading experts in Europe and this book presents a summary of the state of the art, taking examples from recent world-class research. In particular the book presents a number of case studies that have been developed to test compaction models. Full details of data required for input to compaction models of these case studies is given together with a survey of the techniques used to generate the data. Details are also given of methods to produce and assess components for validation of die compaction models. Inclusion of information on case studies then provides a reference for testing and validation of compaction models.


The reader will gain an appreciation of:



  • The requirements in industry for models of die compaction

  • The techniques available to generate the material data required for input to compaction models

  • The production and assessment of compacts for comparison with model predictions

  • A range of compaction models and the results from exercises comparing results from these models with real powder compacts

  • And a range of potential uses and modes of use of compaction models in industry.
Voir plus Voir moins
Contents
Lists of Contributors and Project Partners......................................................xvii
1 Introduction....................................................................................................... 1 P.Brewin, O.Coube, P.Doremus and J.H.Tweed1.1 Treatment of Main Subjects in Compaction Modelling...................................... 2 1.2 Summaries of Individual Chapters.. ................................................................... 2
2 Modelling and Part Manufacture.................................................................... 7P.Brewin, O.Coube, J.A.Calero, H.Hodgson, R.Maassen and M.Satur2.1 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.Cocks3.1 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.Coube4.1 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.Doremus5.1 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.Doremus6.1 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.Doremus7.1 Introduction ...................................................................................................... 95 7.2 Tensile Test ...................................................................................................... 96 7.3 Diametral Compression Test............................................................................. 98 7.4 Simple Compression Test ............................................................................... 100
Contents
xiii
7.5 Concluding Comments ................................................................................... 103 References………………………………………………………………………..103
8 Friction and its Measurement in Powder-Compaction Processes ............ 105 D.T.Gethin, N.Solimanjad, P.Doremus and D.Korachkin8.1 Introduction .................................................................................................... 105 8.2 Friction Measurement by an Instrumented Die............................................... 107 8.3 Friction Measurement by a Shear Plate .......................................................... 111 8.4 Example Measurements .................................................................................. 112  8.4.1 Instrumented-Die Measurements ........................................................... 112  8.4.2 Shear-Plate Experiments........................................................................ 115 8.5 Factors that Affect Friction Behaviour ........................................................... 118  8.5.1 Surface Properties .................................................................................. 118  8.5.2 Compact and Process Influences ........................................................... 122 8.6 Other Friction Measurement Methods ............................................................ 125 8.7 Relevant Bibliography .................................................................................... 127 8.8 Concluding Comments ................................................................................... 127 References........ .................................................................................................... 128 Chapter Bibliography ........................................................................................... 128
9 Die Fill and Powder Transfer ...................................................................... 131 S.F.Burch, A.C.F.Cocks, J.M.Prado and J.H.Tweed9.1 Introduction .................................................................................................... 131 9.2 Potential Sigificance of Die Fill Density Distribution .................................... 132 9.3 Die-Filling Rig................................................................................................ 133 9.4 The Flow Behaviour of Powder into Dies Containing Step-like Features ...... 136 9.5 Metallographic Techniques for Determining Density Variations ................... 139 9.6 Measurement of Die Fill Density Distribution  by X-Ray Computerised Tomography ............................................................ 140  9.6.1 Hardware Components Needed for X-Ray CT ...................................... 141  9.6.2 Technique for the Quantitative Measurement of Density Variations..... 142  9.6.3 Results for Die fill Density Distribution  Using X-Ray Computerised Tomography ............................................. 143 9.7 Modelling of Die Filling ................................................................................. 146 9.8 Concluding Comments ................................................................................... 149 References ............................................................................................................ 149
10 Calibration of Compaction Models ............................................................. 151 P.Doremus10.1 Introduction .................................................................................................. 151 10.2 Calibration of the Drucker-Prager Cap Model ............................................. 151  10.2.1 Elasticity .............................................................................................. 151  10.2.2 Calibration of Yield Stress Surface and Plastic Strain.  Method Based on Simple Tests........................................................... 152 10.3 Calibration of the Cam-Clay Model ............................................................. 158 10.4 Calibration of the Drucker-Prager Cap Model from Triaxial Data............... 159 10.5 Comparison of the Two Calibrations............................................................ 161
xiv
Contents
10.6 Concluding Comments ................................................................................. 163 References ............................................................................................................ 163
11 Production of Case-Study Components....................................................... 165 T.Kranz, W.Markeli and J.H.Tweed11.1 Introduction .................................................................................................. 165 11.2 Press Instrumentation for Force and Displacement ...................................... 166  11.2.1 Punch Force ......................................................................................... 166  11.2.2 Punch Travel ........................................................................................ 169 11.3 Side Effects of Load Buildup – Press and Punch Deflections ...................... 171  11.3.1 Press Deflections.................................................................................. 171  11.3.2 Punch Deflections ................................................................................ 173  11.3.3 Implications for the Acquired Position Values .................................... 176  11.3.4 Concluding Comments on System Deflections.................................... 177 11.4 Case-Study Components .............................................................................. 177 References ............................................................................................................ 178
12 Assessing Powder Compacts......................................................................... 179 S.F.Burch, J.A.Calero, M.Eriksson, B.Hoffman, A.Leuprecht, R.Maassen, F.M.M.Snijkers, W.Vandermeulen and J.H.Tweed12.1 Introduction .................................................................................................. 179 12.2 Density Distribution by the Archimedes Method ......................................... 180  12.2.1 Hardmetals ........................................................................................... 180  12.2.2 Zirconia and Sm-Co Samples .............................................................. 181 12.3 Density Determination by Machining .......................................................... 185 12.4 Density Distribution Determined by SEM-EDS Line Scan  of Polished Cross-Sections ........................................................................... 187  12.4.1 General Considerations on Density Measurements  of Green Samples.......................................................................................... 187  12.4.2 Samples................................................................................................ 188  12.4.3 Experimental Procedure....................................................................... 188  12.4.4 SEM-EDS Method to Determine Density Distribution........................ 189  12.4.5 Results.................................................................................................. 189  12.4.6 Discussion and Conclusion .................................................................. 190 12.5 Density Determination by X-ray Computerised Tomography...................... 190 12.6 Comparison of Result of Density Distribution Measurement Techniques ... 192 12.7 Determination of Defect Distribution ........................................................... 193 12.8 Concluding Comments ................................................................................. 195 References ............................................................................................................ 195
13 Case Studies: Discussion and Guidelines..................................................... 197 O.Coube and P.Jonsén13.1 Introduction .................................................................................................. 197 13.2 Constitutive Parameters Sensitivity .............................................................. 198  13.2.1 Case Study 3 ........................................................................................ 198  13.2.2 Constitutive Model used for the Parameter Study ............................... 199  13.2.3 Influence of the Constitutive Parameter R ........................................... 200
Contents
xv
 13.2.4 Influence of the Hardening for High Density Values .......................... 202  13.2.5 Looking for Good Agreement with Experimental Values ................... 205  13.2.6 Discussion............................................................................................ 207 13.3 Framework for the Numerical Simulation .................................................... 207 13.4 Influence of Meshing.................................................................................... 211 13.5 Influence of the Initial and Process Data ...................................................... 212  13.5.1 Reference Case .................................................................................... 213  13.5.2 Influence of the Fill Density Distribution ............................................ 214  13.5.3 Influence of the Punch Kinematics ...................................................... 217  13.5.4 Discussion............................................................................................ 220 13.6 Conclusions and Guideline ........................................................................... 221 References ........................................................................................................... 222
14 Modelling Die Compaction in the Pharmaceutical Industry ..................... 223 I.C.Sinka and A.C.F.Cocks14.1 Introduction .................................................................................................. 223 14.2 Pharmaceutical Formulations and Processes ................................................ 225 14.3 Rotary Tablet Press Production Cycle .......................................................... 226  14.3.1 Die Fill on Rotary Presses.................................................................... 227  14.3.2 Compression and Ejection ................................................................... 229 14.4 Tablet Compaction Modelling...................................................................... 230  14.4.1 Material Characterisation for Model Input .......................................... 230  14.4.2 Friction................................................................................................. 233 14.5 Case Studies ................................................................................................. 234  14.5.1 Case Study 1: The Density Distribution in Curved-Faced Tablets ...... 235  14.5.2 Case Study 2: The Density Distribution in Bi-layer Tablets................ 237  14.5.3 Case Study 3: The Density Distribution  in Compression Coated Tablets .......................................................... 239 14.6 Summary and Conclusions ........................................................................... 240 14.7 Acknowledgements ...................................................................................... 241 References ............................................................................................................ 241
15 Applications in Industry ............................................................................... 243 P.Brewin, O.Coube, D.T.Gethin, H.Hodgson and S.Rolland15.1 Numerical Simulation of Die Compaction and Sintering of Hardmetal Drill Tips.......... ........................................................ 243  15.1.1 Summary.............................................................................................. 243  15.1.2 Introduction.......................................................................................... 244  15.1.3 Numerical Simulation of Die Compaction........................................... 244  15.1.4 Numerical Simulation of Sintering ...................................................... 248  15.1.5 Discussion and Conclusions ................................................................ 251 15.2 Ceramic Case Studies ................................................................................... 252 15.3 Concluding Comments ................................................................................. 258 References ............................................................................................................ 258
xvi
Contents
A.1 Appendix 1 – Compaction Model Input Data for Powders...................... 259 A.1.1 Distaloy AE Powder ................................................................................... 259 A.1.2 WC-Co Powder........................................................................................... 266 A.1.3 Zirconia Powder. Low- and High-Pressure Closed Die Compaction ......... 275 A.1.4 Samarium Cobalt Powder Low- and High- Pressure  Closed Die Compaction .............................................................................. 286 References........ .................................................................................................... 292
A.2 Appendix 2 – Case Study Components..................................................... 295 A.2.1 Introduction ................................................................................................ 295 A.2.2 Data for Case Study Components............................................................... 296 References........ .................................................................................................... 318
Glossary............................................................................................................... 319
Index .................................................................................................................... 325
http://www.springer.com/978-1-84628-098-6
Un pour Un
Permettre à tous d'accéder à la lecture
Pour chaque accès à la bibliothèque, YouScribe donne un accès à une personne dans le besoin