Characterizing Halbach EMAT Configurations for SH0 Ultrasonic Waves
06 Jan 2021-IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control (IEEE)-Vol. 68, Iss: 5, pp 1866-1875
TL;DR: In this paper, the authors explored the Halbach magnet array pattern as an alternate to the conventional periodic permanent magnet (PPM) structure, and compared the amplitude generated from multiple single-row Halbach EMATs with singlerow PPM EMAT configurations using finite-element-based simulation models for SH0 ultrasonic wave generation.
Abstract: Electromagnetic acoustic transducers (EMATs) can efficiently generate the shear horizontal (SH) guided wave modes. In this article, the Halbach magnet array pattern is explored as an alternate to the conventional periodic permanent magnet (PPM) structure. The magnetic field strength of a Halbach array is significantly higher on one side of the structure while it is weak on the opposite side of the array. This magnetic field distribution enables Halbach EMATs to generate ultrasonic waves with relatively large amplitude. To observe this phenomenon, this study compares the amplitude generated from multiple single-row Halbach EMATs with single-row PPM EMAT configurations using finite-element-based simulation models for SH0 ultrasonic wave generation. This article then presents the ultrasonic wave fields generated by various double-row Halbach EMAT configurations using finite-element-based simulation models and experimentally validated for guided fundamental SH0 mode generated in an aluminum plate specimen. It is observed that distinct ultrasonic guided wave beam patterns be associated and predicted for different double-row Halbach EMAT configurations.
Citations
More filters
10 Oct 2022
TL;DR: In this article , the authors discussed the observation of a simultaneously propagating dual-mode second-harmonic (DMSH) fundamental symmetric (s 0.
Abstract: It is vital to detect material degradation in structures early to ensure their structural safety. Nonlinear ultrasonic techniques in the guided medium are employed to interpret the material nonlinearity by quantifying the harmonic responses from the ultrasonic guided wave. In this work, we discuss the observation of a simultaneously propagating dual-mode second-harmonic (DMSH) fundamental symmetric (s 0 ) mode and an orthogonal-shear horizontal $(\mathbf{sh}_{0}^{\perp})$ mode generated on a weekly nonlinear isotropic elastic plate while excited with a primary shear horizontal (SH 0 ) mode. The presence of two dominant second harmonic modes is the reason for terming the phenomenon DMSH. Numerical simulations demonstrate the existence of dual harmonics on a thin aluminium plate. As the DMSH possesses different group velocities, each wave packet was identified in time domain analysis as separate signals. The observation is validated experimentally, and dual-mode harmonics were determined by a short-time Fourier transform (STFT) analysis of the time domain signal. A locally enhanced material nonlinearity study was conducted via numerical simulations, and the responses from DMSH were studied. It was found that the second-harmonic $\mathbf{sh}_{0}^{\perp}$ mode was sensitive to locally enhanced material nonlinearity, while the second harmonic s 0 and primary SH 0 were seemingly unaffected. Improved insights from this work may provide important implications for accurate early-state defect detection in structural health monitoring and non-destructive evaluation applications of critical structures.
1 citations
DOI•
TL;DR: In this article , the authors discussed the observation of a simultaneously propagating dual-mode second-harmonic (DMSH) fundamental symmetric (s0) mode and an orthogonal-shear horizontal (SH 0) mode generated on a weekly nonlinear isotropic elastic plate while excited with a primary shear horizontal mode.
Abstract: It is vital to detect material degradation in structures early to ensure their structural safety. Nonlinear ultrasonic techniques in the guided medium are employed to interpret the material nonlinearity by quantifying the harmonic responses from the ultrasonic guided wave. In this work, we discuss the observation of a simultaneously propagating dual-mode second-harmonic (DMSH) fundamental symmetric (s0) mode and an orthogonal-shear horizontal $(\mathbf{sh}_{0}^{\perp})$ mode generated on a weekly nonlinear isotropic elastic plate while excited with a primary shear horizontal (SH0) mode. The presence of two dominant second harmonic modes is the reason for terming the phenomenon DMSH. Numerical simulations demonstrate the existence of dual harmonics on a thin aluminium plate. As the DMSH possesses different group velocities, each wave packet was identified in time domain analysis as separate signals. The observation is validated experimentally, and dual-mode harmonics were determined by a short-time Fourier transform (STFT) analysis of the time domain signal. A locally enhanced material nonlinearity study was conducted via numerical simulations, and the responses from DMSH were studied. It was found that the second-harmonic $\mathbf{sh}_{0}^{\perp}$ mode was sensitive to locally enhanced material nonlinearity, while the second harmonic s0 and primary SH0 were seemingly unaffected. Improved insights from this work may provide important implications for accurate early-state defect detection in structural health monitoring and non-destructive evaluation applications of critical structures.
TL;DR: In this paper , an improved periodic permanent magnet electromagnetic acoustic transducer (PPM EMAT) was proposed for defect detection for a U-shaped boom, which has superior frequency response characteristics and acoustic field directivity, which is suitable for detecting large and complex structures.
Abstract: In this research, to solve the problem of the ultrasonic guided wave inspection of a U-shaped boom, an improved periodic permanent magnet electromagnetic acoustic transducer (PPM EMAT) is proposed for defect detection for a U-shaped boom. The acoustic field distribution range of a traditional PPM EMAT is approximately ±20°, and the energy distribution is relatively concentrated. By adjusting the tilt angle between adjacent magnets and coils of a traditional PPM EMAT, an improved PPM EMAT is proposed. The acoustic field distribution range of the improved PPM EMAT is approximately ±30°, and the energy distribution in this range is relatively uniform. The simulation and experimental results show that the improved PPM EMAT has superior frequency response characteristics and acoustic field directivity, which is suitable for detecting large and complex structures. Furthermore, based on the traditional PPM EMAT and the improved PPM EMAT array, combined with the reconstruction algorithm for the probabilistic inspection of damage (RAPID), the damage locations of the double-hole defects of a U-shaped boom are studied. It is shown that the imaging results for defect location using the improved PPM EMATs are better than those found using the traditional PPM EMATs.
References
More filters
Book•
11 Aug 2014
TL;DR: The semi-analytical finite element method (SAFE) has been used for guided wave modeling as discussed by the authors, which has been shown to be useful in the analysis and display of non-destructive testing.
Abstract: Preface Acknowledgments 1. Introduction 2. Dispersion principles 3. Unbounded isotropic and anisotropic media 4. Reflection and refraction 5. Oblique incidence 6. Waves in plates 7. Surface and subsurface waves 8. Finite element method for guided wave mechanics 9. The semi-analytical finite element method (SAFE) 10. Guided waves in hollow cylinders 11. Circumferential guided waves 12. Guided waves in layered structures 13. Source influence on guided wave excitation 14. Horizontal shear 15. Guided waves in anisotropic media 16. Guided wave phased arrays in piping 17. Guided waves in viscoelastic media 18. Ultrasonic vibrations 19. Guided wave array transducers 20. Introduction to guided wave nonlinear methods 21. Guided wave imaging methods Appendix A: ultrasonic nondestructive testing principles, analysis and display technology Appendix B: basic formulas and concepts in the theory of elasticity Appendix C: physically based signal processing concepts for guided waves Appendix D: guided wave mode and frequency selection tips.
823 citations
Book•
03 Dec 2010
TL;DR: In this paper, the authors present a survey of EMAT techniques and their applications in the industrial domain, including on-line texture monitoring of steel sheets and in-situ monitoring of Dislocation Mobility.
Abstract: Preface. Introduction: Noncontact Ultrasonic Measurements. Brief Historical Sketch of EMAT. Electromagnetic Acoustic Resonance - EMAR. Part I: Development of EMAT Techniques. 1: Coupling Mechanism. 1.1. Background. 1.2. Generation Mechanism. 1.3. Receiving Mechanisms. 1.4. Comparison with Measurements. 2 : Available EMATS. 2.1. Bulk-Wave EMATs. 2.2. Longitudinal-Guided-Wave EMAT for Wires and Pipes. 2.3. PPM EMAT. 2.4. Meander-Line Coil SH-Wave EMAT. 2.5. SH-Wave EMAT for Chirp Pulse Compression. 2.6. Axial-Shear-Wave EMAT. 2.7. SH-Wave EMAT for Resonance in Bolt Head. 2.8. Rayleigh-Wave EMAT. 2.9. Line-Focusing EMAT. 2.10. Trapped-Torsional-Mode EMAT. 2.11. EMATs for High Temperature Measurements. 3: Brief Instruction To Build EMATs. 3.1. Coil. 3.2. Magnets. 3.3. Impedance Matching. Part II: Resonance Spectroscopy with EMATs -EMAR-. 4: Principles of EMAR for Spectral Response. 4.1. Through-Thickness Resonance. 4.2. Spectroscopy with Analog Superheterodyne Processing. 4.3. Determination of Resonance Frequency and Phase Angle. 5: Free-Decay Measurement For Attenuation And Internal Friction. 5.1. Difficulty of Attenuation Measurement. 5.2. Isolation of Ultrasonic Attenuation. 5.3. Measurement of Attenuation Coefficient. 5.4. Correction for Diffraction Loss. 5.5. Comparison with Conventional Technique. Part III: Physical-Acoustics Studies. 6: In-Situ Monitoring Of Dislocation Mobility. 6.1. Dislocation-Damping Model for Low Frequencies. 6.2. Elasto-Plastic Deformation in Copper. 6.3. Point-Defect Diffusion toward Dislocations in Deformed Aluminum. 6.4. Dislocation Damping after Elastic Deformation in Al-Zn Alloy. 6.5. Recovery and Recrystallization in Aluminum. 7: Elastic Constants and Internal Friction of Advanced Materials. 7.1. Mode Control in Resonance Ultrasound Spectroscopy by EMAR. 7.2. Inverse Calculation for Cij and Qij-1. 7.3. Monocrystal Copper. 7.4. Metal-Matrix Composites (SiCf/Ti-6Al-4V). 7.5. Lotus-Type Porous Copper. 7.6. Ni-Base Superalloys. 7.7. Thin Films. 7.8. Piezoelectric Material (Langasite: La3Ga5SiO14). 8: Nonlinear Acoustics. Part IV: Industrial Applications. 9: On-Line Texture Monitoring Of Steel Sheets. 9.1. Texture of Polycrystalline Metals. 9.2. Mathematical Expressions of Texture and Velocity Anisotropy. 9.3. Relation between ODCs and r-Values. 9.4. On-Line Monitoring with Magnetostrictive-Type EMATs. 10: Acoustoelastic Stress Measurements. 10.1. Nonlinear Elasticity. 10.2. Acoustoelastic Response of Solids. 10.3. Birefringence Acoustoelasticity. 10.4. Practical Stress Measurements with EMAR. 10.5. Monitoring Bolt Axial Stress. 11: Measurements On High-Temperature Steels. 11.1. Velocity Variation at High Temperatures. 11.2. Solidification-Shell Thickness of Continuous Casting S
287 citations
235 citations
TL;DR: In this paper, a periodic-permanent-magnet (PPM) EMAT is placed inside the pipe, which generates and receives the SH guided waves traveling in the circumferential direction with the axial polarization.
Abstract: An EMAT technique has been developed to detect corrosion defects on the outer surfaces of steel pipelines. A periodic-permanent-magnet (PPM) EMAT is placed inside the pipe, which generates and receives the SH guided waves traveling in the circumferential direction with the axial polarization. Wheels installed on the PPM-EMAT facilitate the linear movement in the axial direction and are useful for a quick inspection. At each point in scanning, the amplitude and phase shift of the round-trip signals in the SH0 and SH1 modes are measured using a superheterodyne phase-sensitive detector. They respond uniquely to surface defects and provide relevant information for locating axial positions of defects and evaluating the depth. The amplitude and phase shift of the SH1 mode are more sensitive to the presence of the defects than those of the SH0 mode. This technique is useful even if the protective resin coating is tightly glued on the pipes and lowered the signal intensity.
204 citations
TL;DR: A description is given of its various scientific and engineering applications, including the study of wave dispersion in structures, global and long-range inspection of steel pipes and tubes, condition monitoring of machinery such as combustion engines, and onboard sensing of crash events for vehicle safety system operations.
193 citations