What is the eddy current test?
Eddy current testing is an advanced technique in non-destructive testing (NDT) that is used to simplify the quality and maintenance of materials, products and structures in various testing processes. This method is used to identify surface and subsurface defects in any type of portable product and material.
The scope of quality control in production processes is related to the principles of eddy current inspection. Today’s eddy current NDT testing techniques have advanced functions in complex engineering applications, inspection of heat exchanger tubes, testing of advanced aerospace components, etc.
Eddy current test principles
In its simplest form—the single-element eddy current probe—a coil of conductive wire is excited by an alternating electric current. This coil produces an alternating magnetic field around itself, the direction of which is determined by the right-hand rule.The magnetic field oscillates with the same frequency as the current passing through the coil. As the coil approaches the conducting material, currents opposite to those in the coil are induced in the material – eddy currents.
Changes in the electrical conductivity and magnetic permeability of the test object and the presence of defects cause changes in eddy currents and corresponding changes in phase and amplitude, which can be detected by measuring the impedance changes in the coil. This is the basis of the standard eddy current (pancake winding) test.
The eddy current test has a wide range of applications. Since the eddy current test is electrical in nature, it is limited to conductive materials. There are also physical limitations to the generation of eddy currents and penetration depth.Advantages • Computerized record keeping: minor
• Faster inspection
• Better identification capability
• Easier analysis due to simpler scan patterns
• Improved positioning and measurement due to encrypted data
• Identify, locate and isolate defects faster
