Eddy-current testing
DENSIN ROLEN
QA/QC WELDING INSPECTOR (CSWIP 3.1 , PCN RT INTERPRETATION & NDT LEVEL -2(RT, UT ,PT,MT),BE. MECHANICAL ENGINEERING) & AUTO CAD 3D
Eddy current testing (ECT) as a technique for testing finds its roots in?electromagnetism.?Eddy currents?were first observed by?Fran?ois Arago?in 1824, but French physicist?Léon Foucault?is credited with discovering them in 1855. ECT began largely as a result of the English scientist?Michael Faraday's discovery of?electromagnetic induction?in 1831. Faraday discovered that when there is a closed path through which current can circulate and a time-varying 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.[1]
Much of the development of ECT as a?nondestructive testing?technique for industrial applications was carried out during?World War II?in?Germany. Professor?Friedrich F?rster?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, F?rster founded a company, now called the?Foerster Group?where he made great strides in developing practical ECT instruments and marketing them.[2]
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.[2]