Eddy current testing is one of the methods of non-destructive testing of parts made of conductive materials. It is based on the analysis of the interaction of the external electromagnetic field with the electromagnetic field of eddy currents induced in the test piece by this field.
The eddy current testing method is based on the analysis of interaction of an external electromagnetic field with an electromagnetic field of eddy currents induced by an exciting coil in an electrically conducting test piece by this field. As the source of an electromagnetic field, an inductive coil (one or more) is commonly used, which is called an eddy current transducer (EDT).
A sinusoidal (or pulsed) current acting in the eddy current coils creates an electromagnetic field that excites eddy currents in an electromagnetic object. The electromagnetic field of eddy currents affects the converter coils, inducing EMF in them or changing their total electrical resistance. By getting the voltage on the coils or their resistance, information is obtained about the properties of the object and the position of the relative transducer. The peculiarity of eddy current control is that it can be carried out without contact between the converter and the object. Their interaction occurs at distances sufficient for the free movement of the transducer relative to the object (from fractions of millimeters to several millimeters). Therefore, these methods can provide good test results even at high object velocity.
- In aviation. The eddy current method is used to test structures made of conductive materials in aircraft:
• wheel hubs
• blades compressor blades and turbine of gas turbine engines
• power elements of airframe
- In railway transport, eddy current testing is used to assess a track condition.
- In pipe production to inspect straight seam of pipes