| 摘要 |
<p>Fissures extending in any direction are revealed on the surface of ferromagnetic test pieces by means of the magnetic particle procedure. The magnetisation is carried out by the application of two magnetic fields directly following each other and with field vectors at the perpendicular to each other. One field is prod. by field circulation and the other by current circulation, the sample being supplied with test medium the while. A.C is used to supply the magnetic field. The latter's strength as well as that of the current flow are faded out after a stipulated function by means of an adjustment control when a min. effective time has elapsed for forming an indication. The second field is applied shortly before, or at the latest with, the start of the adjustment control for the first field applied to the sample.</p> |
