Eddy Current Non-destructive Testing Applications - Flaw Detection

Ether NDE possesses the expertise and offers a wide range of equipment for eddy current (ECT) non-destructive testing (NDT) aimed at all the application requirements of their customers. Flaw detection, particularly surface and sub-surface crack detection as well as sub-surface corrosion detection, is the most common application.

Surface Crack Detection

Generally, this is performed using either “pancake” type probes or pencil probes on ferrous or non-ferrous metals. Usually, frequencies ranging from 100 kHz to a few MHz are used. Normally, it is possible to detect cracks of 0.1 mm or less in depth based on surface condition. Thanks to the focused field of the shielded probes, the test can be performed very close to edges or different materials such as ferrous fasteners in an aluminum structure can be tested.

Occasionally, differential probes are used, mainly in automated applications. However, care must be exercised to make sure that the orientation of flaws is accurate for detection.

Sub-Surface Crack/Corrosion Detection

This is predominantly used in airframe testing. Eddy currents can penetrate aluminum or similar materials to a depth of about 10 mm by using an appropriate probe and a low frequency. This enables the detection of second and third layer cracking, which is undetectable from the surface, or thinning of any of the distinct layers that form the structure.

In general, test frequencies are in the range of 100 Hz to 10 kHz. Furthermore, the size of the probe should be two or more times broader than the required penetration depth.

This information has been sourced, reviewed and adapted from materials provided by Ether NDE Ltd.

For more information on this source, please visit Ether NDE Ltd.

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