Eddy Current Testing Overview and Techniques


Eddy current testing or electromagnetic testing is based on the science of electric current being induced in conductors when the magnetic field around them changes. This flow of eddy current with changing magnetic field finds application in locating and sizing minute cracks and defects existing on the surface, can estimate the thickness of coatings, and can assist in determine the material make up (i.e. alloy) a test element.

The current is characterised by closed loops that start to make a magnetic field of their own. As a result, the magnetic field produced by the eddy current and the initial magnetic field opposes each other. The eddy current produced by a material in its pure form will differ from the eddy current produced by the material when present in an altered or defect form. This difference in the creation of a magnetic field is what gets primarily used for NDT or non-destructive testing of materials.

How the process works?

In order to produce eddy current, alternating current is made to flow through a conducting coil. These current starts to produce a magnetic field surrounding the coil. A test piece that is a good conductor of electricity is placed in this field of the probe and the eddy current is induced in the piece. If the test piece is fine, then the eddy currents produced will be of different magnitude than the eddy current that is produced when the material has cracks and defects and imperfections.

When a second probe is used, it can detect the difference in eddy current. In some of the areas, the coil impedance is measured to find the defect.

The eddy current testing method is commonly used in high-end complex industrial processes in the automotive industry, the aerospace, and the electronics industry. The method is a highly advanced method of non-destructive testing. The fact that it is non-invasive, and it can work in sync with a computerised system to display and store results, makes it a popular choice amongst testing methods. It can detect even minutest defects and cracks on the material surface. Therefore, it is used in high-end and sophisticate manufacturing environments.


Location: Perth WA, Australia

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