Chapter 1 General Introduction of Deep-sea Spherical Pressure Hulls 1

1.1Application scenario of deep-sea spherical pressure hulls 2

1.2 The design methodology of deep-sea pressure hull 6

1.2.1 Shape selection 6

1.2.2 Material selection 8

1.2.3 Hull thickness requirement based on the depth limit and safety factor 9

1.2.4 End closures design compatible with the hull and design requirement 9

1.3 Other considerations to ensure safety 10

1.3.1 Reliability 10

1.3.2 Fatigue and fracture 12

1.3.3 Model test 14

1.3.4 Seal design 16

1.4 Manufacturing process of deep-sea pressure hulls 17

References 21

Chapter 2 Material Selection for Deep-sea Spherical Pressure Hulls 23

2.1 Candidate materials for deep-sea spherical pressure hulls 24

2.1.1 Steels 26

2.1.2 Aluminium alloys 28

2.1.3 Titanium alloys 28

2.1.4 Acrylic plastics (polymethyl methacrylate) 29 2.1.5

Composites 30

2.2 Practice for material selection 31

2.2.1 Selection of titanium alloys 33

2.2.2 Selection of maraging steels 44

References 50

Chapter 3 Linear Buckling Mechanics of Deep-sea Spherical Pressure Hulls 53

3.1 Overview of current rules for spherical pressure hulls 53

3.1.1 Introduction of rules 53

3.1.2 Comparison of rules 59

3.2 Analytical analysis 62

3.2.1 Strength evaluation 62

3.2.2 Stability evaluation 69

3.3 Numerical analysis 76

3.3.1 Brief introduction of FEM principle 76

3.3.2 Numerical study of different methods 82

References 92

Chapter 4 Nonlinear Buckling of Deep-sea Spherical Pressure Hulls 94

4.1 Overview of current studies 94

4.1.1 Empirical formulae 94

4.1.2 Phenomenological models 104

4.2 Elastic-plastic buckling analysis 107

4.2.1 Titanium alloy spherical pressure hulls 107

4.2.2 Maraging steel spherical pressure hulls 124

4.3 Experimental study in laboratory scale 127

4.3.1 Materials and methods 128

4.3.2 Results and discussion 132

References 143

Chapter 5 Fatigue Life Assessment Theory for Deep-sea Spherical Pressure Hulls 146

5.1 Analysis methods for fatigue of spherical pressure hulls 147

5.1.1 Loading history of the spherical pressure hull 148

5.1.2 Low-cycle fatigue theory based on strain-cycles curve 152

5.1.3 Methods based on crack growth theory 158

5.1.4 A simplified life estimation method 185 References 192

Chapter 6 Testing and Numerical Simulation of Deep-sea Spherical Pressure Hulls 195

6.1 Verification testing 197

6.1.1 Ultimate compression-carrying capacity testing for scale model 198

6.1.2 Hydrostatic pressure testing for viewports 207

6.1.3 Function testing for hatch-cover opening and closing mechanism 209

6.2 Inspection testing 210

6.2.1 Material properties testing 210

6.2.2 Geometrical size measurement 213

6.3 Acceptance testing 214

6.3.1 Leakage testing 214

6.3.2 Hydrostatic pressure testing 215

6.4 Numerical Simulation 216

6.4.1 Structural strength calculation of the deep-sea spherical pressure hull using FEA method 216

6.4.2 Numerical simulation on collapse of the deep-sea spherical pressure hull 221

6.4.3 The simulation of transient dynamic process of crushing 226

References 233