EMAT Design of Self-excitation with Coils and Its Characteristics Study

doi:10.3901/JME.2017.16.134

Abstract

Abstract: An electromagnetic acoustic transducer(EMAT) model of self-excitation with coils is proposed. The new EMAT can avoid attraction between the magnet and ferromagnetic particles, as there is no need of magnet providing field. Furthermore, the weight of the EMAT reduces dramatically. Characteristics of the EMAT are investigated by both finite element and experimental methods. A₀ Lamb wave attenuates more rapidly than S₀ Lamb wave. At the lift-off distance of 6 mm, the dynamic magnetic field still has a large horizontal component to excite S₀ Lamb wave by magnetostriction mechanism. In comparison, A₀ Lamb is mainly generated by dynamic Lorentz force. Both the current density and the dynamic magnetic field attenuate markedly after 3 mm, leading to the rapid decrease of out-of-plane vibration produced by dynamic Lorentz force. The coil-only EMAT is able to generate pure S₀ Lamb at the lift-off of 6 mm. This distance is much higher than traditional EMATs, which is usually lower than 3 mm. Finally, directionality of the lamb waves is studied and S₀ Lamb is more suitable for wide range detection because of the longer wavelength.

Key words: EMAT, Lamb wave, lift-off distance, lorentz force, magnetostriction force

CLC Number:

TP212

HE Jianpeng, XU Ke, REN Weiping. EMAT Design of Self-excitation with Coils and Its Characteristics Study[J]. Journal of Mechanical Engineering, 2017, 53(16): 134-140.

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