High Temperature Shear Horizontal Electromagnetic Acoustic Transducer for Guided Wave Inspection

Kogia, Maria; Gan, Tat-Hean; Balachandran, W.; Livadas, Makis; Kappatos, Vassilios; Szabó, István; Mohimi, Abbas; Round, Andrew M.

doi:10.3390/s16040582

Cited by 32 publications

(22 citation statements)

References 30 publications

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“…Fig. 14. The normalized amplitude of S0 Lamb waves that from the results of the experiments, the simulation and the traditional Lorenz based EMAT which is configured with several periodic permanent magnets and a racetrack coil [17]. The error bars indicate the deviation versus the average value of the experiment results.…”

Section: Methodsmentioning

confidence: 99%

“…The normalized results are shown in Fig. 14. For ease of comparison, both the simulation results and the results from traditional Lorenz based EMAT [17] are also shown in the Fig. 14. The simulation result is in a good accordance with the experiment result.…”

Section: Methodsmentioning

confidence: 99%

“…The result is very significant for studying the excitation efficiency of EMATs via the magnetostrictive mechanism. With an increase of temperature, the magnetic permeability and electrical conductivity of iron decreases sharply [28,29], so that the contribution to ultrasonic generation by the Lorentz force mechanism decreases [17,18]. However, the increase of the magnetostriction coefficient means that the contribution to ultrasonic generation by the magnetostriction mechanism may increase with the increasing temperature.…”

Section: Magnetostriction Curves At Different Temperaturesmentioning

confidence: 99%

“…IntroductionElectromagnetic acoustic transducers (EMATs) are used in non-destructive testing (NDT) as they offer several benefits including their non-contacting nature and their ability to generate and detect a range of wave modes [7,12,13] that are difficult to achieve using conventional transducers. The non-contact nature of EMATs makes them suitable for NDT applications where the object under test is at an elevated temperature or is moving [14][15][16][17][18]. EMATs have poor electro-mechanical efficiency as either generators or detectors and can have complicated coupling mechanisms for ferromagnetic materials, where both magnetoelastic and Lorentz mechanisms contribute to transduction.…”

mentioning

confidence: 99%

“…Therefore, the efficiency of EMATs is related to the EMAT lift-off from the surface of the sample, the EMAT design and the physical properties of the sample, including electrical conductivity, magnetic permeability, Young's modulus, etc., which can be significantly affected by the temperature [28][29][30]. In high temperature applications, the efficiency of EMAT as a generator or detector usually reduces drastically, due to the reduction of Lorentz force, linked to a decrease in the electrical conductivity of the sample [17,18,22]. This paper focuses on the contribution of the magnetostriction mechanism to the EMAT when a low-carbon steel sample is at elevated temperature.…”

mentioning

confidence: 99%

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A study of magnetostriction mechanism of EMAT on low-carbon steel at high temperature

Ren

Dixon

et al. 2019

NDT & E International

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The Electromagnetic acoustic transducer (EMAT) is used in a number of non-destructive testing applications [1][2][3][4][5]. The EMAT's operation is principally based on one of two mechanisms; the Lorenz force and magnetostriction mechanism [6-9]. The magnetostriction mechanism of an EMAT at elevated temperatures is reported in this paper. An optimized model is developed to describe the magnetostriction of polycrystalline iron, which is based on Brown's magnetic domain wall movement model [10] and Lee's magnetic domain rotation model [11]. The magnetostriction curves of polycrystalline iron for the temperature range 300 K to 900 K are predicted, which reveal that the saturated magnetostriction coefficient changes from to approximately . A non-linear, isotropic magnetostriction, finite element model is developed to simulate the Lamb waves generated in 4 mm thick steel plate by an EMAT, and the results show that the amplitude of S0 Lamb wave is greatly enhanced with an increase of temperature. In the experiments, a magnetostriction-based EMAT is used to generate Lamb waves in 4 mm thick steel plate. Experimental measurements verify that the contribution of the magnetostriction mechanism on steel rises as temperature increases in the range 298 K to 873 K, while the contribution to ultrasonic generation from the Lorenz force mechanism decreases, as expected. Key wordsElectromagnetic acoustic transducer, magnetostriction mechanism, high temperature, finite element model, low-carbon steel 1. IntroductionElectromagnetic acoustic transducers (EMATs) are used in non-destructive testing (NDT) as they offer several benefits including their non-contacting nature and their ability to generate and detect a range of wave modes [7,12,13] that are difficult to achieve using conventional transducers. The non-contact nature of EMATs makes them suitable for NDT applications where the object under test is at an elevated temperature or is moving [14][15][16][17][18]. EMATs have poor electro-mechanical efficiency as either generators or detectors and can have complicated coupling mechanisms for ferromagnetic materials, where both magnetoelastic and Lorentz mechanisms contribute to transduction. Research has been undertaken in an attempt to improve the efficiency of the EMAT and better understand the physics behind the coupling mechanisms involved [7,8,[19][20][21][22][23]. In operating on non-ferromagnetic materials, the EMAT has only Lorentz force mechanisms to consider. In ferromagnetic materials, magnetostriction and magnetisation mechanisms must also be considered [7,8]. Research on the quantization of the Lorentz force mechanism and magnetostriction mechanism has shown that, for the conventional EMAT that can operate via both mechanisms, the Lorentz force is usually the main contributor [24,25] to the

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%