| 摘要 |
<p>A method and apparatus is disclosed to characterise a part with respect to an axis through the part.The part is exemplified as a ferromagnetic shaft (10) rotatable about a longitudinal axis (A-A). A source of magnetisation (22), a permanent magnet or an electromagnet, is located adjacent the shaft (10) to magnetise the local surface-adjacent zone (12) of the shaft (10). The shaft is rotated so that the local magnetisation carries to a magnetic field detector (26) axially aligned with, but angularly offset from, source (22). The output from the detector (26) varies with angle in accordance with some magnetic property of the shaft (10). The shaft (10) may be given an axial translation by means (16) to enable the surface of the shaft (10) to be successively scanned. An alternative arrangement uses an in-line source and detector. A particular application is to investigating the uniformity of case-hardening of steel shafts.</p> |
