| 摘要 |
PURPOSE:To feed back a powerful reflected wave in an exact direction and to improve the sensitivity in ultrasonic flaw detection in the case of detecting the flaw of a non-magnetic material by applying a magnetic flux of a high density in a strong magnetic field to the inside of an object to be inspected by a small- sized transducer and generating a powerful ultrasonic wave. CONSTITUTION:Small-sized permanent magnets 20a-20f are adjacently arranged by paralleling the directions where the magnetic poles thereof line up and disposing the magnetic poles of the permanent magnets oppositely to each other. A thin sheet-like ferrite core 11 is attached and united to the one side face where the magnetic poles line up thereby constituting a magnetic circuit. Magnetic fluxes B1-B5 are applied at intervals T0 on an object 13 to be inspected by the magnetic field generated in the direction of the S pole from N between the adjacent permanent magnets. When high frequency current IH is conducted in a coil 22 opposite to the magnetic fluxes, eddy currents I1-I5 are generated in the body 13 in parallel with the coil 22. An ultrasonic wave is generated in the body 13 by the Lorentz forces F1-F5 generated by the mutual effect between the eddy currents and the magnetic fluxes and is semi-infinitely propagated therein. |
