Contents
Foreword
Preface
Chapter 1 Dehydration efficiency of high-frequency pulsed DC electrical fields on water-in-oil emulsion 1
1.1 Introduction 1
1.2 Model development 2
1.2.1 Define of emulsion stability index 2
1.2.2 Define of dehydration efficiency index 3
1.3 Experiments 6
1.3.1 Preparation of emulsion 6
1.3.2 Experimental instrumentation 7
1.3.3 Relationship between conductivity and measured current 9
1.4 Results and discussion 9
1.4.1 The relationship between measured current and droplets behaviour 9
1.4.2 Influence of the inter-electrode distance 11
1.4.3 Influence of the frequency 14
1.4.4 Influence of the pulse duration 17
1.4.5 Influence of the water contents 19
1.4.6 Influence of surfactant concentration 20
1.4.7 Influence of initial droplets size 21
1.4.8 Influence of sodium chloride concentration in the dispersed phase 23
1.4.9 Influence of temperature 25
1.5 Conclusions 26
Chapter 2 Simulation of droplet behavior in water-in-oil emulsion subjected to an electric field 27
2.1 Introduction 27
2.2 Kinetic modeling of droplets 28
2.2.1 Forces acting on droplets 28
2.2.2 Electric forces 29
2.2.3 Viscous forces 31
2.2.4 Coulomb force and gravity 32
2.3 Simulation 32
2.3.1 Assumptions 32
2.3.2 Coalescence probability 32
2.3.3 Simulation strategy 34
2.4 Experiments 35
2.5 Results and discussion 36
2.6 Conclusions 42
Chapter 3 Application of variable frequency technique on electrical dehydration of water-in-oil emulsion 43
3.1 Introduction 43
3.2 Experiments 45
3.2.1 Preparation of emulsion 45
3.2.2 Experimental instrumentation 46
3.2.3 Define of dehydration efficiency index 47
3.3 Results and discussion 47
3.3.1 The relationship between measured current and droplets behaviour 47
3.3.2 Dehydration efficiency of the pulsed electric field with constant frequency 49
3.3.3 Dehydration efficiency of the pulsed electric field with changing frequency 51
3.4 Conclusions 54
Chapter 4 Discussion of the drop rest phenomenon at millimeter scale and coalescence of droplets at micrometer scale 55
4.1 Introduction 55
4.2 Theory 56
4.2.1 Stochastic model for the drop-interface and droplet-droplet coalescence 56
4.2.2 Model for the droplets behavior in electric field based on conductivity technique 60
4.3 Materials and methods 62
4.3.1 Materials and preparation of W/O emulsions 62
4.3.2 Experimental conditions 62
4.3.3 Experiments on the measurement of surface and interfacial tension 62
4.3.4 Experiments on interfacial coalescence of drops 62
4.3.5 Experiments on droplets coalescence in pulsed DC electric filed 63
4.4 Results and discussion 64
4.4.1 Adsorption at water-oil interfaces 64
4.4.2 Interfacial coalescence of drops 65
4.4.3 Emulsion stability in pulsed DC electric filed 67
4.5 Conclusions 69
Chapter 5 Investigation of the charging characteristics of micron sized droplets based on parallel plate capacitor model 71
5.1 Introduction 71
5.2 Principle 73
5.3 Experimental section 77
5.4 Results and discussion 79
5.4.1 Validation of the method 79
5.4.2 Influence of electrical field strength and ion species 80
5.4.3 Influence of electrolyte concentration 81
5.4.4 Influence of droplets size 82
5.5 Comparison with high electrical field strength 82
5.6 Conclusions 86
Chapter 6 Investigation on the influence of the dielectrics on the material removal characteristics of EDM 87
6.1 Introduction 87
6.1.1 Type of currently used dielectrics 88
6.1.2 Role of the dielectrics 89
6.1.3 Investigation strategy of this work 91
6.2 Experimental work 92
6.2.1 Experimental set-up 92
6.2.2 Experimental procedure 92
6.2.3 Rebuilt of the crater with 3D-CAD software 94
6.3 Results and discussion 95
6.3.1 Definition of the crater shape 95
6.3.2 Diameter, depth and volume 96
6.3.3 Removal efficiency 101
6.3.4 Transient simulation of the discharge generated bubble 102
6.4 Conclusions 106
Chapter 7 Transient dynamics simulation of the electrical discharge generated bubble in sinking EDM 107
7.1 Introduction 107
7.2 Transient dynamics modeling 109
7.2.1 Assumptions 109
7.2.2 Model and boundary conditions 111
7.2.3 Modeling of the bubble 111
7.2.4 Governing equation 112
7.3 Discussion of the simulation 112
7.3.1 Propagation of the blast wave 113
7.3.2 Pressure at the center of the discharge spot on the workpiece’s surface 114
7.3.3 Force applied on the electrodes 114
7.3.4 Velocity field in the gap 115
7.4 Experiments and results 117
7.4.1 Shape characters of discharge crater 118
7.4.2 Volume of removed material and removal efficiency 120
7.4.3 Vibration intensity of workpiece 121
7.5 Conclusions 122
Chapter 8 A novel method of determining energy distribution and plasma diameter of EDM 124
8.1 Introduction 124
8.2 Energy distribution model of EDM 126
8.2.1 Principle 126
8.2.2 Heat conduction analysis 127
8.3 Experimental work 131
8.4 Results and discussion 133
8.4.1 Determination of Xdeb 133
8.4.2 Determination of Xcon and Rpc 134
8.4.3 Influence of polarity and dielectric 139
8.4.4 Comparison with previous researches and discussion 139
8.5 Conclusions 141
Chapter 9 Sinking EDM in water-in-oil emulsion 142
9.1 Introduction 142
9.2 Experiments and methods 144
9.2.1 Preparation of emulsion 144
9.2.2 Viscosity of emulsion 145
9.2.3 Experimental set-up 145
9.3 Results and discussion 147
9.3.1 Comparison of EDM machining characteristics using kerosene and W/O emulsion at different peak currents 147
9.3.2 Comparison of kerosene and W/O emulsion at different pulse durations 156
9.4 Discussion of the gap phenomenon 159
9.5 Conclusions 162
Chapter 10 Study of the recast layer of a surface machined by sinking EDM using water-in-oil emulsion as dielectrics 164
10.1 Introduction 164
10.2 Experimental procedures 166
10.3 Results and discussion 168
10.3.1 SR and RLT 168
10.3.2 Oxide existed in the recast layer 171
10.3.3 XRD measurement 173
10.3.4 EDS measurement 174
10.3.5 Micro-cracks and micro-voids in the recast layer 176
10.3.6 Micro hardness 180
10.4 Conclusions 182
References 184