Electromagnetic Acoustic Transducers (eBook)

Preface to the Second Edition 6
Preface to the First Edition 8
Contents 11
1 Introduction 17
Abstract 17
1.1 Contact and Noncontact Measurements 17
1.2 Brief Historical Sketch of EMAT 20
1.3 Electromagnetic Acoustic Resonance - EMAR 24
References 25
Development of EMAT Techniques 28
2 Coupling Mechanism 29
Abstract 29
2.1 Background 29
2.2 Generation Mechanism 30
2.2.1 Governing Equations 30
2.2.2 Dynamic Magnetic Fields in a Ferromagnetic Material 31
2.2.3 Lorentz Force 35
2.2.4 Magnetization Force 37
2.2.5 Magnetostriction Force 38
2.3 Receiving Mechanisms 45
2.4 Comparison with Measurements 46
2.4.1 SH Plate Wave 47
2.4.2 Bulk Shear Wave 50
References 51
3 Available EMATs 53
Abstract 53
3.1 Bulk-Wave EMATs 53
3.2 Longitudinal-Guided-Wave EMAT for Wires and Pipes 56
3.3 PPM EMAT 59
3.4 EMAT for Torsional Wave along Pipes 60
3.5 Meander-Line-Coil SH-Wave EMAT 60
3.6 SH-Wave EMAT for Chirp Pulse Compression 61
3.7 Axial-Shear-Wave EMAT 64
3.8 SH-Wave EMAT for Resonance in Bolt Head 66
3.9 Rayleigh-Wave EMAT 67
3.10 Line- and Point-Focusing EMATs 67
3.11 Trapped-Torsional-Mode EMAT 70
3.12 EMATs for High-Temperature Measurements 73
3.13 Antenna Transmission Technique for Piezoelectric Materials 77
References 79
4 Brief Instruction to Build EMATs 82
Abstract 82
4.1 Coil 82
4.2 Magnets 85
4.3 Impedance Matching 86
4.3.1 L-Matching Network 86
4.3.2 Voltage Step-up Ratio 88
4.3.3 Example 1: Meander-Line-Coil EMAT 88
4.3.4 Example 2: Bulk-Wave EMAT with a Spiral Coil 90
Resonance Spectroscopy with EMATS-EMAR 93
5 Principles of EMAR for Spectral Response 94
Abstract 94
5.1 Through-Thickness Resonance 94
5.2 Spectroscopy with Analog Superheterodyne Processing 97
5.3 Determination of Resonance Frequency and Phase Angle 101
References 102
6 Free-Decay Measurement for Attenuation and Internal Friction 103
Abstract 103
6.1 Difficulty in Attenuation Measurement 103
6.2 Isolation of Ultrasonic Attenuation 104
6.3 Measurement of Attenuation Coefficient 105
6.4 Correction for Diffraction Loss 106
6.4.1 Diffraction Phenomena Radiated by a Bulk-Wave EMAT 107
6.4.2 Correction at a Resonant State 109
6.5 Comparison with Conventional Technique 110
References 112
Physical Acoustic Studies 113
7 In-Situ Monitoring of Dislocation Mobility 114
Abstract 114
7.1 Dislocation Damping Model for Low Frequencies 114
7.2 Elasto-Plastic Deformation in Copper 116
7.3 Point-Defect Diffusion toward Dislocations in Aluminum 123
7.3.1 Diffusion under Stress 123
7.3.2 Activation Energy for Diffusion 129
7.4 Dislocation Damping after Elastic Deformation in Al-Zn Alloy 132
7.5 Recovery and Recrystallization in Aluminum 135
References 138
8 Elastic Constants and Internal Friction of Advanced Materials 141
Abstract 141
8.1 Mode Control in Resonance Ultrasound Spectroscopy by EMAR 141
8.1.1 Difficulty of Mode Identification 141
8.1.2 Mode Selection Principle 143
8.2 Inverse Calculation for Cij and Qij?1 145
8.3 Monocrystal Copper 148
8.4 Metal Matrix Composites (SiCf/Ti-6Al-4V) 153
8.4.1 Difficulty of Measuring Cij of Anisotropic Composites 153
8.4.2 Cross-Ply and Unidirectional Composites 154
8.4.3 Cij and Qij?1 at Room Temperature 155
8.4.4 Micromechanics Modeling 159
8.4.5 Elastic Constants of a Single SiC Fiber 163
8.4.6 EMAR at High Temperatures 164
8.5 High-Temperature Elastic Constants of Titanium through hcp-bcc Phase Transformation 168
8.6 Lotus-Type Porous Copper 170
8.7 Ni-Base Superalloys 174
8.8 Thin Films 176
8.8.1 Anisotropy of Thin Films 176
8.8.2 Thickness Resonance of Layered Plate 177
8.8.3 Free-Vibration Resonance of Layered Rectangular Parallelepiped 180
8.8.4 Ni-P Amorphous Alloy Thin Film 181
8.9 Resonance Measurements at Elevated Temperatures for Piezoelectric Materials 185
8.9.1 Langasite (La3Ga5SiO14) 186
8.9.2 ?-Quartz 191
8.9.3 Phonon-Assisted Hopping Conduction of Carriers in GaN 194
References 195
9 Resonance Ultrasound Microscopy 200
Abstract 200
9.1 Local Elastic Stiffness 200
9.2 Isolation of Oscillator 201
9.3 Vibrational Analysis 203
9.4 Young’s Modulus Imaging 206
9.5 Portable Young’s Modulus Tester 210
References 214
10 Nonlinear Acoustics for Microstructural Evolution 216
Abstract 216
10.1 Nonlinear Elasticity 216
10.2 Second Harmonic Generation 217
10.3 Collinear Three-Wave Interaction 218
10.4 Nonlinear Resonant Ultrasound Spectroscopy 221
References 223
Industrial Applications 224
11 Online Texture Monitoring of Steel Sheets 225
Abstract 225
11.1 Texture of Polycrystalline Metals 225
11.2 Mathematical Expressions of Texture and Velocity Anisotropy 226
11.3 Relation between ODCs and r-Values 229
11.4 Online Monitoring with Magnetostrictive-Type EMATs 234
References 236
12 Acoustoelastic Stress Measurements 238
Abstract 238
12.1 Higher-Order Elasticity 238
12.2 Acoustoelastic Response of Solids 240
12.3 Birefringence Acoustoelasticity 242
12.4 Practical Stress Measurements with EMAR 246
12.4.1 Axial Stress of Railroad Rails 247
12.4.2 Bending Stress in Steel Pipes 250
12.4.3 Residual Stress in Shrink-Fit Disk 253
12.4.4 Residual Stress in Weldments 254
12.4.5 Two-Dimensional Stress Field in Thin Plates 257
12.5 Monitoring Bolt Axial Stress 261
12.5.1 Shear Wave Acoustoelasticity along the Bolts 261
12.5.2 Combination of Longitudinal/Shear Velocity Ratio 268
12.5.3 SH-Wave Resonance in the Bolt Head 270
References 273
13 Measurement of Induction Hardening Depth 275
Abstract 275
13.1 Sensing Modified Surface Layers 275
13.2 Axial-Shear-Wave Resonance 276
13.3 Linear Perturbation Scheme 278
13.4 Inverse Evaluation of Case Depth 280
References 283
14 Detection of Flaw and Corrosion 285
Abstract 285
14.1 Gas Pipeline Inspection 285
14.1.1 Linear Scanning with PPM EMAT 286
14.1.2 Dispersion Relation of SH Modes 287
14.1.3 Interpretation of Measurements 289
14.2 Total Reflection of SH Modes at Tapered Edges 293
14.3 Flaw Detection by Torsional Modes along Pipes 295
14.4 Line- and Point-Focusing EMATs for Back Surface Defects 299
14.4.1 Line-Focusing EMAT for Detection of Slit Defects 299
14.4.2 Point-Focusing EMAT for Detecting Back Surface Cracks 303
References 306
15 Average Grain Size of Steels 307
Abstract 307
15.1 Scattering of Ultrasonic Waves by Grains 307
15.2 Fourth-Power Law 308
15.3 Steel Specimens and Grain Size Distribution 309
15.4 Grain Size Evaluation 310
References 313
16 Remaining-Life Assessment of Fatigued Metals 315
Abstract 315
16.1 Fatigue and Ultrasonic Measurements 315
16.2 Zero-to-Tension Fatigue of Copper 316
16.3 Rotating-Bending Fatigue of Low-Carbon Steels 323
16.3.1 Specimen Preparation and Measuring Method 323
16.3.2 Attenuation Peak 325
16.3.3 Nonlinearity Peaks 328
16.3.4 Microstructure Observations 328
16.3.5 Mechanism of First Nonlinearity Peak 329
16.3.6 Mechanism of Attenuation Peak and Second Nonlinearity Peak 331
16.3.7 Influence of Interruption of Fatiguing on the Measurements 334
16.4 Tension-Compression Fatigue of Low-Carbon Steels 335
References 338
17 Creep Damage Detection 340
Abstract 340
17.1 Aging of Metals 340
17.2 Creep and Dislocation Damping in Cr-Mo-V Steel 341
17.3 Commonly Observed Attenuation Peak 347
References 348
18 Field Applications of EMATs 349
Abstract 349
18.1 Monumental Work of EMAT Field Applications 349
18.2 Crack Inspection of Railroad Wheels 352
18.3 Residual Stress in Railroad Wheels 353
18.4 Measurement on High-Temperature Steels 354
18.4.1 Velocity Variation at High Temperatures 354
18.4.2 Solidification-Shell Thickness of Continuous Casting Slabs 356
18.5 Wall Thickness of Hot Seamless Steel Tubes 360
18.6 Corrosion of Heat Exchanger Tubes 364
18.7 In-Process Weld Inspection 367
18.7.1 Phased-Array SH-Wave EMAT 367
18.7.2 Laser-EMAT Hybrid Systems 370
References 372
Index 375