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Eddy-current testing (also commonly seen as eddy current testing and ECT) is one of many electromagnetic testing methods used in nondestructive testing (NDT) making use of electromagnetic induction to detect and characterize surface and sub-surface flaws in conductive materials. == History == Eddy current testing (ECT) as a technique for testing finds its roots in electromagnetism. Eddy currents were first observed by François Arago in 1824, but French physicist Léon Foucault is credited with discovering eddy currents in 1855. ECT began largely as a result of the English scientist Michael Faraday's discovery of electromagnetic induction in 1831. Simply put, Faraday discovered that when there is a closed path through which the current can circulate and that a magnetic field passes through a conductor (or vice versa), an electric current flows through this conductor. In 1879, another English-born scientist, David Edward Hughes, demonstrated how the properties of a coil change when placed in contact with metals of different conductivity and permeability, which was applied to metallurgical sorting tests.〔Ivor Hughes. ("The AWA Review: Professor David Edward Hughes" ), 2009, retrieved July 1, 2015〕 Although there were a number of encouraging developments in the 19th century, much of the actual development of ECT as an NDT technique for industrial applications was carried out during World War II in Germany. Professor Friedrich Förster while working for the Kaiser-Wilhelm Institute (now the Kaiser Wilhelm Society) adapted eddy current technology to industrial use, developing instruments measuring conductivity and sorting mixed ferrous components. After the War, in 1948, Förster founded a company known today the (Foerster Group ) where he made great strides in developing practical ECT instruments and marketing them.〔Nikhil Jahain. ("The Rebirth of Eddy Current Testing" ), 2014, retrieved July 1, 2015〕 Eddy current testing is now a widely used and well understood inspection technique for flaw detection, as well as thickness and conductivity measurements. Frost & Sullivan analysis in the global NDT equipment market in 2012 estimated the magnetic and electromagnetic NDT equipment market at $220 million, which includes conventional eddy current, magnetic particle inspection, eddy current array, and remote-field testing. This market is projected to grow at 7.5% compounded annual growth rate to approximately $315 million by 2016.〔Nikhil Jahain. ("The Rebirth of Eddy Current Testing" ), 2014, retrieved July 1, 2015〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Eddy-current testing」の詳細全文を読む スポンサード リンク
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