A type of focused single-mode A0 Lamb wave EMAT for performance improvement

Abstract In this paper, a Halbach array periodic permanent magnet (HPPM) electromagnetic acoustic transducer (EMAT) was proposed for generating stronger and purer A0 mode Lamb wave (A0 wave). Compared to conventional periodic permanent magnets (PPM), the HPPM generates a more intense and purer horizontal magnetic field, enhancing A0 wave amplitude by 28% and suppressing the S0 mode Lamb wave (S0 wave) by 32%. Additionally, a focused A0 wave EMAT (FHPPM-EMAT) with arc structure is proposed. The FHPPM-EMAT demonstrates excellent transduction efficiency and focusing capability. An orthogonal analysis was conducted to evaluate the factors affecting the transduction efficiency of the FHPPM-EMAT. With optimized parameters based on orthogonal analysis, the FHPPM-EMAT achieved a 93% increase in A0 wave amplitude compared to the HPPM-EMAT. Furthermore, the size of the focal area is characterized by a horizontal focal width (Hd) and a vertical focal width (Vd) of only 36.21 mm and 10.45 mm, respectively.