Tunability for anomalous refraction of flexural wave in a magneto-elastic metasurface by magnetic field and pre-stress

2022 ◽  
Author(s):  
Shunzu Zhang ◽  
Shiwei Shu ◽  
Xiaohui Bian
Keyword(s):  
Magnetic Field ◽  
Phase Shift ◽  
Elastic Wave ◽  
Negative Refraction ◽  
Functional Unit ◽  
Flexural Wave ◽  
Refraction Angle ◽  
Mechanical Coupling ◽  
Anomalous Propagation ◽  
Vibration Noise

Abstract This letter reports the design of a magneto-elastic metasurface composed of arrayed Terfenol-D pillars deposited on a homogeneous Aluminum plate, aiming to realize the tunability of flexural wave anomalous propagation without altering the structure. Considering the magneto-mechanical coupling of magnetostrictive materials, the phase shift and transmission of functional unit can be calculated. The anomalous refraction of incident flexural wave (i.e., negative refraction) can be accomplished by adjusting magnetic field and pre-stress properly, the refraction angle is remarkably affected by magnetic distribution. The proposed metasurface provides a method for flexible tunability of elastic wave in the fields of vibration/noise control.

scholarly journals Sensitive measurement of phase shift of an AC magnetic field by quantum sensing with multiple-pulse decoupling sequences

2019 ◽  
Vol 126 (6) ◽  
pp. 064504
Author(s):  
Toyofumi Ishikawa ◽  
Akio Yoshizawa ◽  
Yasunori Mawatari ◽  
Satoshi Kashiwaya ◽  
Hideyuki Watanabe
Keyword(s):  
Magnetic Field ◽  
Phase Shift ◽  
Multiple Pulse ◽  
Ac Magnetic Field ◽  
Quantum Sensing

Electromagnetic damping of elastic waves: Experimental results

1968 ◽  
Vol 5 (4) ◽  
pp. 825-829 ◽  
Author(s):  
F. E. M. Lilley ◽  
C. M. Carmichael
Keyword(s):  
Magnetic Field ◽  
Elastic Wave ◽  
Applied Magnetic Field ◽  
Elastic Waves ◽  
Applied Field ◽  
Eddy Currents ◽  
Electrical Conductor ◽  
Electromagnetic Damping ◽  
The Waves ◽  
The Magnetic Field

The passage of an elastic wave causes straining and translation in the transmitting material. If a magnetic field is applied, and the medium is an electrical conductor, some of the energy of the wave is dissipated by the flow of electrical eddy currents. Usually the amount of energy lost is very small, but it may be greatly increased if the applied field is strongly non-uniform.Laboratory experiments are described which demonstrate this effect for standing elastic waves in a metal bar. The applied magnetic field changes from almost zero to its full strength over a distance which is short compared to the length of the standing wave. The result of this strong non-uniformity is that the energy lost due to the translation of the bar in the field greatly exceeds the energy lost due to the straining of the bar in the field.The dependence of the attenuation of the waves by the magnetic field is investigated for variation in frequency of vibration, bar thickness, and field gradient.

Development of Numerical Code for Coupling Dynamical Response of Typical Tokomak Structures Using Volumetric Finite Element

2013 ◽  
Author(s):  
Zhensheng Yuan ◽  
Weixin Li ◽  
Jingyi Xu ◽  
Wenjing Wu ◽  
Zhenmao Chen
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Coupling Effect ◽  
Time Integration ◽  
Numerical Code ◽  
Dynamical Response ◽  
Vacuum Vessel ◽  
Integration Algorithm ◽  
Simulation Accuracy ◽  
Mechanical Coupling

Aiming to simulate the dynamical response of a non-ferromagnetic conductive structure in a strong magnetic field, a code of finite element method (FEM) was developed based on the reduced vector potential (Ar) method and a step by step time integration algorithm. The electromagneto-mechanical coupling effect was taken into consideration by adding ν × B term in the eddy current governing equation to calculate the additional electric field induced by the movement of the structure. The hexahedral isoparametric element was adopted in this code in order to simplify the correspondence between the simulation of electromagnetic force and the dynamical response, which enables the application of the code developed by authors to more complicated structures. To verify the validity of the new numerical code, the benchmark problem (TEAM-16) as a simplified model of Tokamak vacuum vessel structure was simulated. By numerical results contrasted between the current code and the ANSYS software, the code was proved to be more effective than typical commercial codes for structural analysis of a magneto-mechanical coupling problem. The simulation results proved that the new code can improve simulation accuracy especially in case of a large external magnetic field. In addition, the magnetic damping effect was also discussed in the paper.

scholarly journals Electromagnetic Wave Scattering from a Moving Medium with Stationary Interface across the Interluminal Regime

Photonics ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 202
Author(s):  
Zoé-Lise Deck-Léger ◽  
Xuezhi Zheng ◽  
Christophe Caloz
Keyword(s):  
Electromagnetic Wave ◽  
Wave Scattering ◽  
Negative Refraction ◽  
Current Knowledge ◽  
Moving Medium ◽  
Refraction Angle ◽  
Electromagnetic Wave Scattering ◽  
Transmitted Waves ◽  
Stationary Interface ◽  
Moving Media

This paper extends current knowledge on electromagnetic wave scattering from bounded moving media in several regards. First, it complements the usual dispersion relation of moving media, ω(θk) (θk: phase velocity direction, associated with the wave vector, k), with the equally important impedance relation, η(θS) (θS: group velocity direction, associated with the Poynting vector, S). Second, it explains the interluminal-regime phenomenon of double-downstream wave transmission across a stationary interface between a regular medium and the moving medium, assuming motion perpendicular to the interface, and shows that the related waves are symmetric in terms of the energy refraction angle, while being asymmetric in terms of the phase refraction angle, with one of the waves subject to negative refraction, and shows that the wave impedances of the two transmitted waves are equal. Third, it generalizes the problem to the case where the medium moves obliquely with respect to the interface. Finally, it highlights the connection between this problem and a spacetime modulated medium.

scholarly journals The Magnetic Field Produced by the Heart and Its Influence on MRI

2017 ◽  
Vol 2017 ◽  
pp. 1-9
Author(s):  
Dan Xu ◽  
Bradley J. Roth
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Field ◽  
Phase Shift ◽  
Cardiac Tissue ◽  
Spherical Model ◽  
Motion Artifacts ◽  
Resonance Imaging ◽  
Physiological Noise ◽  
Cardiac Action ◽  
The Magnetic Field

Background. Action currents in the heart produce a magnetic field, which could provide a way to detect the propagation of electrical activity through cardiac tissue using magnetic resonance imaging. However, the magnetic field produced by current in the heart is small. The key question addressed in this study is are cardiac biomagnetic fields large enough to be detectable by MRI? Results. A spherical model is used to calculate the magnetic field inside the heart, which has a magnitude of about 14 nT. This field implies a phase shift in the MRI signal of about 0.2°. Conclusion. Phase shifts associated with cardiac action currents will be difficult to detect using current MRI technology but may be possible if motion artifacts and other physiological noise can be suppressed.

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