A modified design of the omnidirectional EMAT for antisymmetric Lamb wave generation

This work presents a modified design of electromagnetic acoustic transducer (EMAT) that generates only antisymmetric (A0) omnidirectional Lamb wave. The new magnetic configuration includes a solid cylindrical magnet and a ring-shaped magnet surrounding the outside of the solid cylindrical magnet. The diameter of the solid cylindrical magnet is slightly small than the inner diameter of the ring-shaped magnet. The double-turn coil is used instead of a single spiral coil. Numerical simulation is applied to characterize the magnets and determine the coil parameters. Experimental results on a 3 mm-thick aluminum plate show that the modified EMAT we proposed can generate and receive pure single A0 mode Lamb wave with high signal to noise ratio and can effectively meet the imaging requirements.