An Improved Design of the Spiral-Coil EMAT for Enhancing the Signal Amplitude

Jia, Xiaojuan; Ouyang, Qi; Zhang, Xinglan

doi:10.3390/s17051106

Cited by 20 publications

(5 citation statements)

References 26 publications

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“…Pei et al utilized a new permanent magnet arrangement structure to increase the signal amplitude of the surface waves [13]. Jia et al modified the spiral coeil structur and combined it with a new permanent magnet structure to increase the signal amplitude of the body wave [14]. To address the problem that Lamb waves have multiple modes, which can make the analysis of the results difficult, Sun et al used changing the drive frequency and coil parameters to achieve mode selection of Lamb waves [11].…”

Section: Introductionmentioning

confidence: 99%

An EMAT for improving the purity and amplitude of S₀ Lamb waves

Yang

Zhang²,

Wu³

et al. 2022

Meas. Sci. Technol.

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Different waves of the Lamb waves may be superimposed in practical tests due to its multimodal characteristics and dispersion characteristics, thus greatly increasing the difficulty of later signal analysis and creating a huge limitation to their application in non-destructive testing (NDT). Only a single magnet was used to generate a static magnetic field in the traditional S0 mode Lamb wave (S0 wave) electromagnetic acoustic transducer (EMAT), which resulted in a less pure S0 wave. Additionally, the accompanying A0 mode Lamb wave (A0 wave) will decrease the accuracy of the results in defect detection and increase the difficulty of the signal processing. In order to obtain a single-mode S0 wave, a periodic magnet structure EMAT structure was proposed in this study. Finite element models were established and the effect of single and periodic magnet structure on the static magnetic field was analyzed. The periodic magnet structure EMAT can substantially enhance the S0 mode Lamb wave amplitude by increasing the flux density of the local magnetic field using periodically arranged magnets. However, it also causes enhancement to the A0 wave and decreases the detection accuracy. An improved EMAT was further proposed to increase the S0 wave amplitude with no enhancement to the A0 wave amplitude. Experiments were conducted and two types of EMAT were comparatively investigated, which agreed with the simulated results. The S0 wave amplitude can be increased by 7 times with the improved EMAT compared to traditional EMAT, and the A0 wave is completely submerged in the noise. The improved EMAT proposed in this study can provide guidance for the single-mode S0 wave defect detection.

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Section: Introductionmentioning

confidence: 99%

An EMAT for improving the purity and amplitude of S₀ Lamb waves

Yang

Zhang²,

Wu³

et al. 2022

Meas. Sci. Technol.

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“…Electromagnetic acoustic transducers (EMATs) do not require direct contact with the specimen being tested during the detection process, and they outperform piezoelectric transducers without the need for coupling agents and surface pretreatment [8]. Furthermore, EMATs have the capability of operating at high temperatures and high speeds, and in other harsh environments, in addition to having significant advantages in thickness measurement and detection of rail defects due to their good penetration ability [7,9].…”

Section: Introductionmentioning

confidence: 99%

Numerical Study and Optimal Design of the Butterfly Coil EMAT for Signal Amplitude Enhancement

Zhang

Liu

Jia

et al. 2022

Sensors

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The low energy conversion efficiency of electromagnetic acoustic transducers (EMATs) is a critical issue in nondestructive testing applications. To overcome this shortcoming, a butterfly coil EMAT was developed and optimized by numerical simulation based on a 2−D finite element model. First, the effect of the structural parameters of the butterfly coil EMAT was investigated by orthogonal test theory. Then, a modified butterfly coil EMAT was designed that consists of three−square permanent magnets with opposite polarity (TSPM−OP) to enhance the signal amplitude. Finally, the signal amplitude obtained from the three types of EMATs, that is, the traditional EMAT, the EMAT optimized by orthogonal test theory, and the modified EMAT with TSPM−OP, were analyzed and compared. The results show that the signal amplitude achieved by the modified butterfly coil EMAT with TSPM−OP can be increased by 4.97 times compared to the traditional butterfly coil EMAT.

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“…In this paper, a radial-flux-focusing magnet is proposed, inspired by Halbach’s concept, which can provide a stronger magnetic field, thus improving the efficiency of the energy transfer of the longitudinal-wave EMAT and making the measurement signal easier to identify. This work also utilizes two kinds of spiral coils [ 25 ] by changing their size parameters according to the location of the area where the horizontal and vertical components of the magnetic field are concentrated. When dual modes are needed, the amplitude of shear waves and longitudinal waves simultaneously excited by the flux-concentrating EMAT can be increased using the large-diameter coil.…”

Section: Introductionmentioning

confidence: 99%

A New Design of the Dual-Mode and Pure Longitudinal EMAT by Using a Radial-Flux-Focusing Magnet

Zhang

et al. 2022

Sensors

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An electromagnetic acoustic transducer (EMAT) is suitable for measuring the propagation time more accurately without causing abrasion to the transducer during testing due to the principle of its excitation. This work designs a flux-concentrating EMAT with a radial-flux-focusing permanent magnet to significantly enhance static magnetic field strength. Through theoretical analysis and finite element simulation, two kinds of coils are designed according to the concentration areas of the horizontal and vertical components of the magnetic field. One is used to generate pure longitudinal waves, and the other is used to generate both longitudinal waves and shear waves. The experimental comparison shows that the amplitudes of the pure longitudinal wave and the dual-mode wave excited by the two kinds of coils with the radial-flux-focusing magnet are more than two times higher than those with the ordinary magnet. Therefore, the flux-concentrating EMAT with the appropriate coil provides an insight into realizing more accurate detection where longitudinal wave detection is required.

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An Improved Design of the Spiral-Coil EMAT for Enhancing the Signal Amplitude

Cited by 20 publications

References 26 publications

An EMAT for improving the purity and amplitude of S₀ Lamb waves

An EMAT for improving the purity and amplitude of S₀ Lamb waves

Numerical Study and Optimal Design of the Butterfly Coil EMAT for Signal Amplitude Enhancement

A New Design of the Dual-Mode and Pure Longitudinal EMAT by Using a Radial-Flux-Focusing Magnet

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An Improved Design of the Spiral-Coil EMAT for Enhancing the Signal Amplitude

Cited by 20 publications

References 26 publications

An EMAT for improving the purity and amplitude of S0 Lamb waves

An EMAT for improving the purity and amplitude of S0 Lamb waves

Numerical Study and Optimal Design of the Butterfly Coil EMAT for Signal Amplitude Enhancement

A New Design of the Dual-Mode and Pure Longitudinal EMAT by Using a Radial-Flux-Focusing Magnet

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An EMAT for improving the purity and amplitude of S₀ Lamb waves

An EMAT for improving the purity and amplitude of S₀ Lamb waves