CONTENTS
Chapter 1Introduction1
1.1Background and Significance of Topic Selection1
1.2Research Status of Electromagnetic Ultrasonic Guided Wave Inspection of Pipelines3
1.2.1Electromagnetic Ultrasonic Guided Wave Excitation Mechanism3
1.2.2Ultrasonic Guided Waves in Pipelines4
1.3Research Status of Guided Wave Projection Data Extraction Method6
1.3.1Interaction of Guided Waves with Defects6
1.3.2Guided Wave Signal Analysis and Projection Data Extraction8
1.4Research Status of Guided Wave Imaging Methods for Pipeline Defects10
1.5Research Content13
Chapter 2Research on Pipeline Helical Lamb Wave Electromagnetic Ultrasonic Transducers16
2.1Introduction to this Chapter16
2.2Structural Design of Helical Lamb Wave Electromagnetic Ultrasonic Transducer17
2.2.1The Basic Theory of Lamb Wave17
2.2.2Design of Helical Lamb Wave Transducer20
2.3Theoretical Model of the Lorentz Force for the Pipeline Helical Lamb Wave23
2.4Simulation and Verification of the Performance of the Helical Lamb Wave Transducer25
2.5Experimental Verification and Comparative Analysis of Helical Lamb Wave Transducers29
2.5.1Platform Construction and Verification29
2.5.2Comparison with Traditional Transducers32
2.6Chapter Summary36
Chapter 3Ultrasonic Guided Wave Overlapping Signal Separation and Feature Extraction38
3.1Introduction to this Chapter38
3.2Overlapping Signal Separation Identification and Feature Extraction39
3.2.1Dispersion and Multimode Characteristics of Guided Waves39
3.2.2Polynomial Chirplet Transform40
3.2.3Construction of Basis Functions43
3.2.4Instantaneous Frequencies of Non-Stationary Signals45
3.3Overlapping Guided Wave Signal Separation and Feature Extraction Steps46
3.4Verification with Simulation Signal48
3.4.1Boundary Reflection Case49
3.4.2Robustness Verification under Defects with Variable Distance51
3.5Verification and Comparison under Complex Reflection55
3.5.1Considering Overlap from Defects and Boundaries55
3.5.2Further Comparison and Analysis59
3.6Chapter Summary62
Chapter 4Fast Helical Guided Wave Tomography Based on Staight Ray Approximation63
4.1Introduction to this Chapter63
4.2Pipeline MultiHelical Guided Wave Propagation Model64
4.3Probabilistic Reconstruction Imaging Methods66
4.3.1Imaging Models Based on Signal Difference Coefficient66
4.3.2Probabilistic Reconstruction Method Steps69
4.4Verification for Tomography Based on Probabilistic Reconstruction with Simulation Signal70
4.4.1The Single Defect Case70
4.4.2The Double Defect Case74
4.5Verification with Real Complex Defect75
4.5.1Platform Construction and Imaging Verification75
4.5.2Further Comparison and Analysis77
4.6Chapter Summary80
Chapter 5Ultrasonic DiffractionBased HighResolution Helical Guided Wave Tomography81
5.1Introduction to this Chapter81
5.2The Fourier Diffraction Theorem for Cross-hole Tomography82
5.3The Compressed Sensing Tomography87
5.3.1Non-uniform Fast Fourier Transform88
5.3.2Tomographic Reconstruction under Finite Projection91
5.3.3Solution Based on Compressed Sensing94
5.4Procedures of Ultrasound Diffraction-Based Tomography95
5.5Verification with Simulated Staircase Defect for Tomography97
5.6Verification of Tomography with Complex Defect103
5.6.1Verification with Real Complex Defect103
5.6.2Further Comparison and Analysis105
5.7Chapter Summary108
Chapter 6Conclusions and Future Recommendations109
6.1Conclusion109
6.2Recommendations for Further Work111
References112
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