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Alternating Current Field Measurement (ACFM) is an electromagnetic inspection method capable of both detecting and sizing (length and depth) surface-breaking cracks in metals. The basis of the technique is that an alternating current can be induced to flow in a thin skin near the surface of an); conductor. By introducing a remote uniform current into an area of the component under test, when there are no defects present the electrical current will be undisturbed. If a crack is present, the uniform current is disturbed and the current flows around the ends and down the faces of the crack. This paper presents results from slow speed (0.1 m/s) tests on a set of rails which contain artificially induced surface-breaking defects, including half-face slots machined normal to the railhead surface, clusters of angled slots, and pocket-shaped defects (representative of gauge corner cracks), using an ACFM system particularly designed for the inspection of railheads. The trends in crack sizes were successfully determined for the artificial defects. Some discrepancies in calculated crack sizes were found, which have been attributed to the large crack mouth opening of the machined defects. ACFM tests were also performed on rail samples that contained actual RCF defects. Further developments for testing on a rotating rail rig at significantly higher speeds are ongoing.
|Number of pages||5|
|Journal||Insight - Non-Destructive Testing and Condition Monitoring|
|Publication status||Published - 1 Jul 2008|
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- 1 Finished
Davis, C. & Roberts, C.
18/10/05 → 17/03/09
Project: Research Councils