Shear wave generation using a spiral electromagnetic acoustic transducer

Jian, X.; Dixon, S.; Baillie, Iain; Edwards, R. S.; Morrison, James P.; Yang, Fan

doi:10.1063/1.2408644

Cited by 19 publications

(19 citation statements)

References 10 publications

(10 reference statements)

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“…Although such analysis is available for homogeneous particles, 44 the effect of surface heterogeneity on tuning the diffusivity and rotational motion has not been investigated. The translational motion of Janus nanoparticles at liquid interfaces is important to understand interfacial self-assembly processes and to use them as tracer elements in micro-and nanorheology, 45,46 while their orientational motion has implications for their use as catalysts e.g. at oil-water interfaces.…”

Section: Introductionmentioning

confidence: 99%

Molecular simulation of translational and rotational diffusion of Janus nanoparticles at liquid interfaces

Rezvantalab

Drazer

Shojaei-Zadeh

2015

The Journal of Chemical Physics

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We perform molecular dynamics simulations to understand the translational and rotational diffusion of Janus nanoparticles at the interface between two immiscible fluids. Considering spherical particles with different affinity to fluid phases, both their dynamics as well as the fluid structure around them are evaluated as a function of particle size, amphiphilicity, fluid density, and interfacial tension. We show that as the particle amphiphilicity increases due to enhanced wetting of each side with its favorite fluid, the rotational thermal motion decreases. Moreover, the in-plane diffusion of nanoparticles at the interface becomes slower for more amphiphilic particles, mainly due to the formation of a denser adsorption layer. The particles induce an ordered structure in the surrounding fluid that becomes more pronounced for highly amphiphilic nanoparticles, leading to increased resistance against nanoparticle motion. A similar phenomenon is observed for homogeneous particles diffusing in bulk upon increasing their wettability. Our findings can provide fundamental insight into the dynamics of drugs and protein molecules with anisotropic surface properties at biological interfaces including cell membranes.

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Section: Introductionmentioning

confidence: 99%

Molecular simulation of translational and rotational diffusion of Janus nanoparticles at liquid interfaces

Rezvantalab

Drazer

Shojaei-Zadeh

2015

The Journal of Chemical Physics

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“…Detection EMATs used two different designs; a linear coil for directivity measurements [22], and a matched racetrack design to the generation coil for scanning bar samples, to ensure the same spatial frequency response [27]. Both were hand-wound using 0.08 mm diameter wire.…”

Section: Emat Configurationmentioning

confidence: 99%

“…Due to the antisymmetry of the Lorentz force across the central part of the racetrack coil, similar to a 2D view of a spiral coil, the in-plane component of the shear wave will have zero amplitude directly opposite the generation EMAT. A critical angle is expected where there is maximum amplitude due to constructive interference of the shear and head waves [22].…”

Section: Shear Wave Directivitymentioning

confidence: 99%

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Multiple Wavemode Scanning for Near and Far-Side Defect Characterisation

Xiang

Edwards

2020

J Nondestruct Eval

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The combination of ultrasonic inspections using different wavemodes can give more information than is available with single mode inspection. In this work, the response of shear and Rayleigh waves to surface-breaking defects propagating on the nearside and far-side of a sample is investigated. The directivity of shear waves generated by a racetrack coil electromagnetic acoustic transducer (EMAT) is identified and used to set an ideal separation for a pair of transmit-receive EMATs. Defects are indicated by a reduction in the transmitted Rayleigh wave amplitude, and by blocking of the shear wave. Used together, these can identify features in the bulk wave behaviour which are due to near-face surface-breaking defects, and give a full picture of both surfaces. By using a combination of the two wavemodes, the angle of propagation and length of any nearside defects can additionally be identified. A scanning method for samples is proposed.

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“…1. It consists of a single cylindrical permanent magnet placed on top of a pancake-like coil, such that radially polarized waves are generated [7].…”

Section: A Emats Based On the Lorentz Forcementioning

confidence: 99%

Optimization of the Bias Magnetic Field of Shear Wave EMATs

Isla

Cegla

2016

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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The main advantage of electromagnetic acoustic transducers (EMATs) over piezoelectric transducers is that no direct contact with the specimen under test is required. Therefore, EMATs can be used to test through coating layers. However, they produce weaker signals, and hence, their design has to be optimized. This paper focuses on the design of a Lorentz force shear wave EMAT and its application in thickness gaging; special emphasis is placed on the optimization of the design elements that correspond to the bias magnetic field of the EMAT. A configuration that consists of several magnets axisymmetrically arranged around a ferromagnetic core with like poles facing the core was found to give the best results. By using this configuration, magnetic flux densities in excess of 3 T were obtained in the surface of a specimen; the maximum value achieved by a single magnet under similar conditions is roughly 1.2 T. If the diameter of an EMAT ultrasonic aperture is 10 mm, the proposed configuration produces signals roughly 20 dB greater than a single magnet, while for a given overall EMAT volume, signals were greater than 3-6 dB. Linear and radial shear wave polarizations were also compared; a higher mode purity and signal intensity were obtained with the linear polarization

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Shear wave generation using a spiral electromagnetic acoustic transducer

Cited by 19 publications

References 10 publications

Molecular simulation of translational and rotational diffusion of Janus nanoparticles at liquid interfaces

Molecular simulation of translational and rotational diffusion of Janus nanoparticles at liquid interfaces

Multiple Wavemode Scanning for Near and Far-Side Defect Characterisation

Optimization of the Bias Magnetic Field of Shear Wave EMATs

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