Dual-row split meander-line coil EMAT for circumferential A0-mode Lamb waves with full-range magnetic field coupling

Electromagnetic acoustic transducers (EMATs) often exhibit poor conversion efficiency and weak output signals when inspecting circumferential defects in thin-walled pipelines. To address this, a novel EMAT employing a dual-row split meander-line coil (DS-MLC-EMAT) is proposed to enhance detection signal energy. This design incorporates a dual-magnet array to improve bias magnetic field uniformity, with the coil specifically tailored for efficient coupling between the magnetic field and induced eddy currents. Three-dimensional multiphysics simulations confirm a significant enhancement in Lorentz force generation: the peak X-component increases by 40%, and the Z-component within the local focal region triples compared to the conventional structure. Consequently, strain energy for the A0 mode becomes more concentrated, amplifying the displacement response by 109.3%. Experimental results show that the optimised sensor with a 0.5 mm row spacing achieves the maximum received signal amplitude, representing a 144.2% increase over the conventional single-magnet EMAT. This novel full-range magnetic field coupling approach provides an effective new solution for circumferential pipeline inspection.