| 摘要 |
PURPOSE:To enable a flaw detection regardless of the shape in the a defect, by simultaneously detecting changes in the magnetic resistance of a magnetic circuit and changes in the impedance of a detection coil based on variations in eddy current. CONSTITUTION:As a high frequency current is supplied to detection coils 12 and 13 from a high frequency power source 15, an alternating magnetic flux is formed perpendicular to the direction of a defect 14. This alternating magnetic flux runs around a core 11 passing through a part of the surface of material S to be inspected to form a magnetic circuit containing a part of the material S being inspected. Therefore, as any defect 14 intercepting the magnetic circuit will increase the magnetic resistance of the magnetic circuit, an induction voltage is generated in the detection coils 12 and 13 to identify flaws. With the application of an alternating magnetic field to the materials S being inspected, an eddy current flowing over the surface of the material being inspected in the direction roughly perpendicular to the core 11. When a defect exists with the width extending along the orientation of the core 1 such as drill hole in the material S being inspected, the distribution of the eddy current is disturbed due to the defect and thus, the defect is detected as changes in the impedance of the detection coils 12 and 13. |
