Abstract: An electromagnetic acoustic transducer (12, 24) has one or a plurality of magnets for applying a DEC magnetic field to a material (4, 25) under test, and an electrical coil (2, 23) supplied by an alternating current source for, providing an AC magnetic flux within the material under test. A wear plate (16, 26) engages with an slides along the surface of the material under test. The wear plate (16, 26) is of electrically conductive ferromagnetic material and has apertures (17, 31) therein. Thus, both the DC field and the ACT flux can penetrate the material under test and create ultrasonic vibration of that material.

Abstract: An electromagnetic acoustic transducer for exciting ultrasound in a ferromagnetic material under test (2), includes a magnetic unit (6) arranged to be moved relative to the material under test (2) to magnetize a surface layer of the material, and an electrical winding (8) supplied by an alternating current source, the magnetic unit (6) and the electric winding (8), in use, being applied in sequence to the material under test (2) whereby the electrical winding (8) is positioned adjacent the material subsequent to magnetization thereof by the magnetic unit (8), the alternating magnetic flux created by the winding (8) interacting with the remanent magnetization of the material to create ultrasonic vibration of the material.