| 摘要 |
PURPOSE:To attain to enhance the detection accuracy of a flaw part, by arranging an insulating press plate in opposed relation to the terminal surface of the electrode inserted in the hollow part of a cylindrical object to be inspected. CONSTITUTION:After the chucking of electrodes 1, 12 and an object 5 to be inspected was performed, high voltage with a predetermined level is applied between the electrodes 1, 12. When a pinhole 15 is present in the object 5 to be inspected, spark discharge is generated and a discharge current by discharge is detected by an ammeter 2 and the flaw part of the object 5 to be inspected can be discriminated. Because clearances d1, d2 are respectively provided between the terminal surface of the positive electrode 12 and press plates 7, 9 and between the terminal surface of the negative electrode 1 and the press plates 7, 9, the distance of the creeping discharge route between the electrodes 1, 12 becomes longer than that of the discharge route through the pinhole 15 even if both ends of the object 5 to be inspected are not perfectly and closely contacted with the press plates 7, 9 without forming the gaps therebetween and, therefore, the generation of creeping discharge can be certainly prevented by properly setting applied voltage. As a result, the deterioration in detection accuracy due to creeping discharge during inspection is prevented and highly accurate inspection reaching even the end parts of the object 5 to be inspected is enabled. |
