| 摘要 |
PURPOSE:To shorten a flaw detection time, by varying a frequency of an AC current to be supplied to the coil of a probe to change the angle of incidence of an ultrasonic wave generated. CONSTITUTION:An electromagnetic ultrasonic probe comprises a coil 2 and a permanent magnet 1 to be opposed to a material 3 to be inspected. The magnet 1 is made up of rectangular permanent magnet pieces 1a so arranged in parallel and series across the width thereof in two rows that the tops thereof act as S and N poles alternately and a spacer 1b made of a non-magnetic material is inserted between adjacent magnet pieces 1a and 1a. When the coil 2 is fed with an AC current, a metal grid on the surface of the material 3 being inspected vibrates parallel with the surface thereof to generate an ultrasonic wave 4 vertically to the direction of vibration and the ultrasonic wave 4 propagates through the material 3 being inspected at an angle of incidence, which is changed by varying the frequency of a current to be applied to the coil 2. This enables the detection of a flaw across the entire thickness of a butt-weld part simply by performing a scanning along the length of the weld part with a pair of transmitting and receiving probes only once. |
