Eddy Current Inspection
Eddy Current Technology
Eddy current testing (ECT) is a noncontact method for the inspection of metallic parts. The probe, excited with an alternating current, induces an eddy current in the part being inspected. Any discontinuities or material property variations that change the eddy current flow in the part are detected by the probe as a potential defect.
Over the years, probe technology and data processing have continuously progressed so that the eddy current technique is now recognized to be fast, simple, and accurate. This is why the technique is widely used in the aerospace, automotive, petrochemical, and power generation industries in the detection of surface or near-surface defects in materials such as aluminum, stainless steel, copper, titanium, brass, Inconel®, and even carbon steel (surface defect only).
Benefits of Eddy Current
Eddy currents offers the following benefits:
- A quick, simple, and reliable inspection technique to detect surface and near-surface defects in conductive materials
- Can be used to measure the electrical conductivity of materials.
- Measurement of nonconductive coatings
- Hole inspection with the use of a high-speed rotating scanner and surface probe
Eddy Current Probes
Olympus standard eddy current probes are available in different configurations:
- Bolt hole probes
- Surface probes, in various shapes and configurations
- Low-frequency Spot and Ring probes
- Sliding probes
- Wheel probes
- Conductivity probes
- Speciality probes made for specific applications
Reference standards with EDM notches can be manufactured according to the application specifications.
Probes used to perform eddy current inspections are made with a copper wire wound to form a coil. The coil shape can vary to better suit specific applications.
a- The alternating current flowing through the coil at a chosen frequency generates a magnetic field around the coil.
b- When the coil is placed close to an electrically conductive material, an eddy current is induced in the material.
c- If a flaw in the conductive material disturbs the eddy current circulation, the magnetic coupling with the probe is changed and a defect signal can be read by measuring the coil impedance variation.
Surface preparation is minimal. Unlike liquid penetrant or magnetic particle inspection, it is unnecessary to remove the paint from the surface to inspect the parts.
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