| 摘要 |
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.
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