Chapter 1 FUNDAMENTALS ........................................ 11
1.1 Microstructure evolution during deformation ............... 11
1.2 Controlled microstructure formation in hot deformation .... 12
1.3 Advanced conceptions of metals deformation processing
modelling ................................................. 16
Chapter 2 MODELLING OF METAL BEHAVIOUR IN HOT DEFORMATION ..... 19
2.1 The flow stress relationship in hot deformation ........... 19
2.2 Technique for generation and approximation of
compression test data ..................................... 19
2.2.1 Hot-work hardening during high temperature
deformation ........................................ 23
2.2.2 The steady state of flow stress .................... 30
2.2.3 Strain resistance during multi-pass loading ........ 34
2.2.4 Application of stress resistance diagrams in
laboratory simulation of hot forming processes ..... 37
Chapter 3 MODELLING OF THE MICROSTRUCTURE DEVELOPMENT OF
HOT DEFORMED METALS ................................. 43
3.1 Static and dynamic recrystallization ...................... 43
3.1.1 Factors affecting the recrystallization ............ 44
3.2 Modelling of static and dynamic recrystallization ......... 47
3.2.1 Static recrystallization ........................... 47
3.2.2 Relationships of dynamic and metadynamic
recrystallization .................................. 47
3.2.3 Grain size evolution of austenite during high
temperature deformation ............................ 48
3.2.4 Coupling of the thermomechanical and the
microstructure models .............................. 49
3.2.5 Methods of investigation of recrystallization
kinetics ........................................... 50
3.3 Phase transformation of deformed austenite in cooling ..... 51
Chapter 4. MODELLING OF THE FORMING PROCESS .................... 57
4.1 Modelling of the material ................................. 58
4.1.1 Mechanical model ................................... 58
4.1.1.1 Strain state .............................. 58
4.1.1.2 Stress state .............................. 62
4.1.1.3 Constitutive relations for the material
of the workpiece .......................... 63
4.1.1.4 Constitutive relations for the material
of the tools .............................. 68
4.1.2 Thermal model ...................................... 68
4.1.3 Coupling of the models ............................. 68
4.2 Modelling the action upon the deformed body ............... 69
4.2.1 Modelling the action of the tools .................. 69
4.2.2 Modelling the thermal contact with the
environment ........................................ 70
4.3 Modelling the initial state ............................... 70
4.4 Basic system of equations describing the thermo-plastic
problem ................................................... 71
Chapter 5. NUMERICAL SIMULATION OF THE FORMING PROCESS BY
MEANS OF THE FINITE ELEMENT METHOD .................. 74
5.1. Basic relations of the FEM for rigid-plastic and visco-
plastic bodies ............................................ 74
5.1.1. Variational principles and assumptions ............. 74
5.1.1.1 Mechanical state .......................... 74
5.1.1.2 Thermal state ............................. 78
5.1.2 Relations of the FEM for rigid-plastic bodies ...... 78
5.1.2.1 Mechanical state .......................... 79
5.2 FE-calculation of heat transfer ........................... 86
5.3 Coupled thermo-plastic processes .......................... 88
5.4 Remeshing ................................................. 89
5.5 Simulation of microstructure evolution .................... 90
Chapter 6. NUMERICAL SIMULATION OF THERMOMECHANICAL
PROCESSES IN HOT EXTRUSION OF ALUMINIUM PROFILES .... 93
6.1 Modelling of thermomechanical strengthening of extruded
AlCu4Mg-alloy ............................................. 93
6.1.1 Modelling of the mechanical behaviour of the
material ........................................... 94
6.1.2 Microstructure and TMT model ....................... 95
6.2 FE simulation of hot extrusion of AlCu4Mg alloy,
followed by cooling on the press .......................... 97
Chapter 7. DEVELOPMENT OF IMPROVED TECHNOLOGICAL REGIME
IN DIE FORGING ..................................... 103
7.1 Improving of die filling in forging of a steel flange .... 103
7.1.1 Modelling of the material behaviour for the
deformation process (stages 2 to 5) ............... 104
7.1.2 Numerical simulation of stages 2 to 5. Results
and discussion .................................... 106
7.1.3 Thermomechanical treatment of steel flange with
self-tempering (stages 6 and 7) ................... 108
7.1.4 Numerical simulation of the thermal problem ....... 108
Chapter 8. IMPROVING OF THE MICROSTRUCTURE AND THE MECHANICAL
PROPERTIES IN ROLLING OF STEELS .................... 113
8.1 Computer simulation of multi-pass rolling ................ 113
8.2 FEM-rationalized TEMPCOR-process in shape rolling of
steel rods ............................................... 118
Chapter 9. FE SIMULATION OF THE FINE GRAINED MICROSTRUCTURE
EVOLUTION IN STAINLESS STEEL ....................... 124
9.1 Fine grained metal materials in advanced forming
processes ................................................ 124
9.2 Elaborating of thermomechanical schedule for fine-
grained stainless steel .................................. 126
9.2.1 Experimental procedure ............................ 126
9.2.2 Modelling procedure ............................... 127
9.2.2.1 Modelling of the material behaviour in
the hot rolling process .................. 127
9.2.2.2 Modelling of the material behaviour in
the cold torsion process ................. 129
9.2.2.3 Modelling of the material behaviour in
the annealing process .................... 132
9.2.2.4 Modelling of the material behaviour in
the warm forging process ................. 133
9.2.3 Experimental results and discussion ............... 136
9.3 FE-simulation of the complex process ..................... 141
9.3.1 Numerical simulation of the rolling process ....... 141
9.3.2 Numerical simulation of the torsion process ....... 144
9.3.3 FE simulation of gears warm die forging ........... 145
Appendix A .................................................... 156
Appendix В .................................................... 165
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