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Eddy Current Testing, ET

Testing method for materials where a coil is charged with an alternating current to create eddy currents, which differ and indirectly detects when there is a defect in the material surface.

Beskrivning
Illustration of Eddy Current Testing, ET

The process

A coil, positioned above the material to be tested is charged with an alternating current, which creates a magnetic field. This creates opposite alternating currents, hence eddy currents in the material. The eddy currents deviate from their normal current directions if there are defects in the surface of the material which is captured by measurement equipment. Type and size of the current deviations indicate defects in the design.

Eddy Current Testing, ET
Process films
Advantages and disadvantages
In comparison with alternative methods
Sensitive to detect surface defects
Can detect through several layers
Can detect through surface coatings
can be automated
only little prior preparation is required
Portable equipment
No need for direct contact with the object
Very sensitive to magnetic permeability
Will not detect defects parallel to the surface
Not suitable for complex geometries
Not suitable for large areas
Interpretation of the signal is required
Limited to ferromagnetic materials