New Technologies in Electromagnetic Non-destructive Testing (eBook)

Preface 6
Contents 8
1 The Electromagnetic Ultrasonic Guided Wave Testing 12
1.1 Outline 12
1.2 Influencing Factors of EMAT 15
1.2.1 Influence of Wire Spacing of the Coil on the Performance of EMAT 15
1.2.2 The Influence of the Number of Foldings on the Performance of EMAT 16
1.2.3 The Influence of Coil Liftoff on the Performance of EMAT 16
1.3 EMATs for the Generation of Guided Waves Along the Axial Direction of the Pipe 17
1.3.1 The Modes of Axial Guided Waves and Frequency Dispersion 17
1.3.2 The Structure of Axial Guided Wave EMAT and Its Transduction Principle 18
1.4 The Dispersion Characteristics of the Guided Waves 20
1.4.1 The Dispersion Characteristics of the Lamb Waves in the Plate 20
1.4.2 The Dispersion Characteristics of the SH Guided Waves in the Plate 21
1.5 The Electromagnetic Ultrasonic Guided Wave Testing Technique 22
1.5.1 Thickness Measurement Based on Electromagnetic Ultrasound 22
1.5.2 Electromagnetic Ultrasonic Guided Wave Testing Along the Axial Direction of the Pipeline 29
1.5.2.1 Hardware of System of the Electromagnetic Ultrasonic Guided Wave Testing Along the Axial Direction of the Pipeline 29
1.5.2.2 Experiment of the Axial Electromagnetic Ultrasonic Guided Wave Testing and the Influencing Factors 34
1.5.3 Electromagnetic Ultrasonic Guided Wave Testing for Cracks in the Natural Gas Pipeline 46
References 50
2 The Pulsed Eddy Current Testing 52
2.1 Basic Principle of Electromagnetism 53
2.1.1 The Penetration Depth and the Skin Effect 54
2.1.2 Principle of Probe Design 56
2.1.3 Principle of the Pulsed Eddy Current Testing 57
2.2 The Coil Sensors in the Pulsed Eddy Current Testing 59
2.2.1 Classifications of the Testing Coils 60
2.2.2 Working Modes of the Testing Coils 60
2.2.3 Probes of the Pulsed Eddy Current Testing 61
2.2.3.1 Requirements of the Working Conditions of the Pulsed Eddy Current Testing 62
2.2.3.2 Selection of the Material of the Probe Magnetic Core 63
2.2.3.3 Winding of the Probe Coil 65
2.2.3.4 Supression of the Liftoff Effect of the Probe 66
2.2.3.5 Sensors with Closed Magnetic Circuits 69
2.2.3.6 The Two-Level Differential Probe 70
2.2.3.7 Rotating Magnetic Field Probe 73
2.2.3.8 Probe with a Cup-Shaped Magnetic Core 75
2.2.3.9 Cross-Winding Probe 77
2.2.3.10 Star-Shaped Coil Probe 78
2.2.3.11 The Horizontal–Vertical Coil Probe 80
2.2.3.12 The Improved Horizontal–Vertical Coil Probe 82
2.2.4 The Reciprocity Rule in Probe Design 83
2.3 Circuits of the Pulsed Eddy Current Testing 83
2.3.1 The Power Supply Module 84
2.3.2 The Excitation Source 86
2.3.3 The Analog Signal Processing Module 87
2.3.4 The Microcontroller Subsystem 88
References 90
3 The Remote-Field Eddy Current Testing 92
3.1 Outline 92
3.2 The Mathematical Model of the RFEC in the Pipeline 95
3.2.1 Basic Equations 95
3.2.2 The Propagation of the AC Magnetic Field in the Ferromagnetic Pipe Wall 99
3.2.3 The Voltage Signal of the Receiving Coil 101
3.3 The FEM Modeling of the RFEC in the Pipeline 102
3.3.1 Introduction to the FEM and ANSYS 102
3.3.2 Building the Remote-Field Eddy Current Model 106
3.4 2D FEM Simulation of RFEC in Pipeline 116
3.4.1 Electromagnetic Decomposition Analysis 120
3.4.2 The Evaluation Model of the Magnetic Field at the Inner Pipeline Surface 123
3.4.3 Analysis of the Full Circumferential Defect 125
3.4.4 Relation of the Defect Signal with the Dimensions of the Defect 129
3.5 3D FEM Simulation of the RFEC in the Pipeline 132
3.5.1 Signal of the Groove Defect 132
3.5.2 Relationship Between Axial Defect Signal and Defect Size 139
References 146
4 Low-Frequency Eddy Current Testing 147
4.1 Introduction 147
4.2 Finite Element Simulation of Eddy Current Coils 148
4.2.1 The Finite Element Modal of Coils 148
4.2.2 Result of Probe Coil Finite Element Simulation 150
4.2.2.1 The Influence of Difference Between Inner and Outer Diameter on Detecting Resolution 150
4.2.2.2 The Influence of Thickness of Probe Coil on Detecting Resolution 153
4.2.2.3 The Influence of Equivalent Radius of Probe Coil on Detecting Resolution 156
4.2.3 Theoretical Analysis of Probe Coil Model 160
4.2.3.1 The Influence of Difference Between the Inner Radius and the Outer Radius of Probe Coil on Magnetic Field Yielded by the Probe 160
4.2.3.2 The Influence of the Thickness of Probe Coil on Magnetic Field Yielded by the Probe 163
4.2.3.3 The Influence of the Equivalent Radius of Probe Coil on Magnetic Field Yielded by the Probe 167
4.3 Pipe Deformation Detecting System Based on Low-Frequency Eddy Current 170
4.3.1 Systematic Design 170
4.3.2 Digital Alternating Current Bridge Measuring Circuit 171
4.3.3 Signal Processing and Display Module 175
References 177
5 Metal Magnetic Memory Testing 179
5.1 Introduction 179
5.2 The Relationship Between Metal Magnetic Memory and Geomagnetic Field 180
5.2.1 The Influence of Geomagnetic Field to Metal Magnetic Memory Testing 180
5.2.2 The Influence of Geomagnetic Field to Metal Magnetic Memory Generation 185
5.2.3 Stress Distribution Detection by Metal Magnetic Memory Testing Method 189
References 193
6 Magnetic Flux Leakage Testing 194
6.1 Introduction 194
6.2 Magnetic Flux Leakage Testing Principle 196
6.3 The Influence Factors of Magnetic Flux Leakage Testing 198
6.3.1 The Thickness of Material 199
6.3.2 The Component of Material 199
6.3.3 The Coupling Loop 199
6.3.4 The Space Between Magnetic Poles 199
6.3.5 The Speed of Inspector 200
6.3.6 The Remanence 201
6.3.7 The Internal Stress 202
6.3.8 The Lift off of Probe 202
6.4 Defect Quantification Method of Magnetic Flux Leakage Testing 205
6.4.1 Defect Quantification Method Based on Statistical Identification 206
6.4.2 Defect Quantification Method Based on Radial Basis Function Neural Network (RBFNN) 211
6.4.3 Defect Quantification Method Based on Three-Dimensional Finite Element Neural Network 217
6.4.3.1 Discretization Principle of Finite Element Method 217
6.4.3.2 Finite Element Neural Network 220
6.4.3.3 From One Dimension to Three Dimension 225
6.4.3.4 Solving Positive and Inverse Problems Using FENN 228
References 230