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Loading...Micro-scaled Products Development via Microforming
Deformation Behaviours, Processes, Tooling and its Realization
Contents
1 Introduction 1
1.1 Introduction . 1
1.2 Size Effects in Microforming . 2
1.3 Size Effect Affected Deformation Behaviors . 3
1.4 Microforming Processes . 4
1.5 Flow-Induced Defects in Microforming 4
1.6 Microforming Process of BMGs . 5
1.7 Summary . 5
References 5
2 Size Effects in Micro-scaled Plastic Deformation 9
2.1 Introduction . 9
2.2 Flow Stress in Micro-scaled Plastic Deformation 9
2.2.1 Strengthening Behavior 10
2.2.2 Modified Hall–Petch Relation 12
2.2.3 Grain Boundary Surface Area-Based Model 13
2.2.4 Mixture Model 17
2.2.5 Surface Layer Model 25
2.3 Deformation Behavior 26
2.3.1 Anisotropic Properties of Single Grain . 27
2.3.2 Modeling of Deformation Behavior 29
2.4 Fracture Behavior . 38
2.4.1 Fracture Strain and Fractograph 38
2.4.2 Grain Statistics 42
2.5 Elastic Recovery 47
2.6 Surface Roughening 47
2.7 Summary . 50
References 51
xi3 Size Effect in Tooling-Workpiece Interface 57
3.1 Introduction . 57
3.2 Experiments . 60
3.3 Results and Discussion 60
3.3.1 Specimen Geometry Size Effect on Interfacial
Friction . 60
3.3.2 Deformation Behavior of Surface Asperity . 62
3.3.3 Fraction of Real Contact Area . 65
3.3.4 Asperity Size Effect 67
3.3.5 Annealing and Grain Size Effects . 68
3.4 Summary . 71
References 71
4 Microforming Processes 73
4.1 Introduction . 73
4.2 Micro Deep Drawing . 75
4.2.1 Interfacial Friction . 75
4.2.2 Process Window . 76
4.2.3 Workpiece and Grain Size Effects . 79
4.3 Microembossing 86
4.3.1 Stamping and Hydroforming 87
4.3.2 Rubber Pad Forming 89
4.4 Micropunching/Microblanking . 90
4.4.1 Deformation Behavior . 91
4.4.2 Deformation Pressure . 94
4.4.3 Ultimate Shear Strength 97
4.4.4 Flexible Tooling . 98
4.5 Microcoining . 100
4.6 Microextrusion . 100
4.6.1 Interfacial Friction . 101
4.6.2 Size Effect . 103
4.6.3 Warm Forming 106
4.6.4 Other Microextrusion Processes 107
4.7 Microheading 109
4.8 Micro Progressive Forming . 116
4.8.1 Microextrusion in Thickness Direction . 120
4.8.2 Fracture Surface . 123
4.9 Summary . 124
References 126
xii Contents5 Flow-Induced Defects in Mesoforming Processes 131
5.1 Introduction . 131
5.2 Folding Defect Formation Mechanism . 133
5.2.1 Experimental Setup . 133
5.2.2 FE Simulation 137
5.3 Feature-Based Method for Defect-Free Forming Process
Determination 140
5.3.1 Detailed Approaches to Avoiding the Folding
Defects . 143
5.4 Summary . 148
References 148
6 Micropart Fabrication Using Bulk Metallic Glasses 151
6.1 Introduction . 151
6.2 Properties of Metallic Glasses . 155
6.2.1 Initial Atomic Structure and Thermal Properties . 156
6.2.2 Flow Stress 157
6.2.3 Strain Rate Sensitivity . 159
6.2.4 Properties of the Deformed Metallic Glasses . 160
6.2.5 Heat- and Deformation-Induced Hardening 162
6.2.6 Process Window . 164
6.3 Microimprinting-Based Processes 165
6.4 Part Ejection in Steel Die-Based Microforming Process . 169
6.5 Summary . 172
References
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