Eddy Current Inspection

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Eddy current is used electromagnetic induction to detect flaws in conductive materials and there are only can tested the conductive materials. Eddy current also used to detect surface cracks, pits, subsurface crack, corrosion on inner surfaces and to determine alloy and heat treat condition. Besides that, standard eddy current test is required a near-surface technique and there are useful for detecting near-surface and variations in materials composition. Eddy current also can used to measure the thickness of non-electrically conductive coatings on electrically conductive substrates. Based on this reason, it can detecting corrosion damage and other damage that causes a thinning measurement on aircraft skins and in walls or tubing used in assemblies such as heat exchanger. In most steels, eddy current testing is limited to surface examination due to the relatively high permeability of these materials. As the response the inspection of weld in ferritic steels can be problematic, the change in the magnetic is dominating permeability across the weld. However, special types of probes have been developed (differential coils) to lessen the effects to material changes and permit the detection of small flaws. Three basic functions such as generating, receiving and displaying will be performed due to the eddy current test instrument. An alternating current is provided by the generating portion of the unit to the test coils. For display, the receiving section processes the signal from the test to the required form and amplitude. Instrument output or display consist of a variety of visual, audible, storage, or transfer techniques utilizing meters, video display, chart recorder, alarm, magnetic tape, computer, and electrical or electronic relays. In standard eddy current testing, a circular coil carrying an AC current is placed in close proximity to an electrically

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