| 摘要 |
PURPOSE:To enable to perform a high-sensitive finding of a defect through the detection of a defect existing at the inside of a material as an impedance of a defect finding coil, by a method wherein an eddy current, generated by an electromagnetic inductive action, is used, and simultaneously, excitation, produced by a direct current, is used in combination. CONSTITUTION:A defect finding coil 1 forms a coil with a diameter which is sized so that a material W to be checked can pierce through the inside of the coil, and the coil is constituted such that it has a winding of 3,000-6,000T and a length of 20-100mm., and a coil current 1, being 60Hz frequency and 50- 80mA, flows. A DC bias exciting coil 2 and said defect finding coil are lined up. The coil 2 is sized in a diameter equal to that of the coil 1, has a winding of 10,000-151,000T, and the length of the coil is set so that a DC current 1 of 50- 100mA flows in a direction of an arrow mark. This constitution permits the detection of each defect as a change factor of an impedance at a high sensitivity. |
