| 摘要 |
PURPOSE:To improve the efficiency of electromagnetic ultrasonic detection by using a simple, small-sized magnetic core by putting a superconductor between magnetic poles of the magnetic core, and increasing the magnetic resistance between the magnetic poles through its diamagnetic operation and reducing leak magnetic flux between the magnetic poles. CONSTITUTION:A closed magnetic path which is formed by a flat and spiral coil 1 while penetrating a material 4 to be inspected consists of a loop l1 passing the magnetic poles 2a and 2b and a loop l2 passing magnetic poles 2b and 2c. Leak magnetic flux le is formed at a distance from the material 4 to be inspected in addition to the magnetic loops l1 and l2 where one piece of magnetic flux passes, and the magnetic flux density nearby the surface of the material 4 is reduced. Further, the superconductor is put between the magnetic poles 2a and 2b, and 2b and 2c of the magnetic core 3 and then the magnetic resistance between the magnetic poles increases by its diamagnetic operation, so that the magnetic flux is concentrated on the loops l1 and l2 weight passing through the superconductor. Consequently, the magnetic flux density on the surface of the body to be inspected can be increased, so the detection efficiency can easily be increased by the small-sized magnetic core. |
