Electro-Magnetic Acoustic Transducer (EMAT) for both Lamb and Shear Horizontal Wave Transduction

An electro-magnetic acoustic transducer comprising:

• a magnet array having a plurality of magnets with alternating polarizations, the magnets being arranged in columns and rows so that the alternating polarizations form a checkerboard pattern;
• a coil;
• wherein at least one of the magnet array and the coil is movable between (i) a first position in which the coil is placed relative to the magnet array such that legs of a coil segment of the coil are positioned along respective boundaries between columns of the checkerboard pattern of alternating polarizations and (ii) a second position in which the coil is placed relative to the magnet array such that the legs of the coil segment of the coil are positioned along respective center lines of columns of the checkerboard pattern of alternating polarizations;
• and
• wherein a Lamb wave is generated when the coil is excited with an electrical current while in the first position and a shear horizontal wave is generated when the coil is excited with an electrical current while in the second position.

An electro-magnetic acoustic transducer comprising:

• a magnet array having a plurality of magnets with alternating polarizations, the magnets being arranged in columns and rows so that the alternating polarizations form a checkerboard pattern;
• a coil placed relative to the magnet array such that legs of a coil segment of the coil are positioned along respective boundaries between columns of the checkerboard pattern of alternating polarizations;
• and
• wherein a Lamb wave is generated when the coil is excited with an electrical current.

An electro-magnetic acoustic transducer comprising:

• a magnet array having a plurality of magnets with alternating polarizations, the magnets being arranged in columns and rows so that the alternating polarizations form a checkerboard pattern;
• a coil;
• a magnetic conducting material layer between the magnet array and the coil, the magnetic conducting material layer configured to direct the checkerboard pattern of alternating polarizations of the magnet array to (i) a first position in which the coil is placed relative to the magnet array such that legs of a coil segment of the coil are positioned along respective boundaries between columns of the checkerboard pattern of alternating polarizations and (ii) a second position in which the coil is placed relative to the magnet array such that the legs of the coil segment of the coil are positioned along respective center lines of columns of the checkerboard pattern of alternating polarizations;
• and
• wherein a Lamb wave is generated when the coil is excited with an electrical current while in the first position and a shear horizontal wave is generated when the coil is excited with an electrical current while in the second position.