Introduction
Eddy current testing is a form of non-destructive testing used to detect surface and subsurface flaws or irregularities in metallic materials and electrically conductive non-metallic materials. Eddy current testing is used across many industries including aerospace, automotive, military, industrial, fabrication and aerospace.
History
Eddy current testing was first discovered in 1824 by a French physicist, Andre-Marie Ampere, who discovered that a current flowing in a wire could cause itself to deflect if there was a metallic object close by. The deflection he predicted is known today as an eddy current. During World War II, eddy current testing emerged as a reliable method for aircraft inspections. It has been used in the aviation industry ever since, and today, eddy current testing is accepted as one of the primary methods of aircraft inspections.
Advantages
The primary advantage of using eddy current testing is its ability to detect flaws and irregularities in materials without causing any damage to the surface or subsurface of the material being tested. This saves time and money because it prevents the need to re-manufacture parts, and it can detect flaws even when the material is protected by a coating such as paint or chrome plating. Additionally, the nondestructive nature of eddy current testing means that it can be used to inspect components already in service, allowing for continuous operational testing.
Inspection Techniques
Eddy current testing can be used in a variety of different inspection techniques. The most basic technique is flaw detection, which uses a probe to detect flaws and discontinuities on the surface or subsurface of a material. Another technique is resonance detection, which uses a pulsed excitation current to detect defects that are in resonance. Finally, one of the most advanced techniques is Eddy current array inspection, which uses an array of electrodes to map defects and scan larger areas.
Applications
Eddy current testing can be used to detect a broad range of flaws and discontinuities. Common applications include detecting fatigue and corrosion cracks, surface porosity, inclusions, and subsurface defects. Eddy current testing is also used to detect and measure linear wall thickness and identify invisible alterations caused by welding, machining, brazing and other processes. Additionally, eddy current testing can be used to test electrical insulation, measure the amount of remaining core, detect the amount of material left on a surface, and verify the integrity of drive shafts.
Conclusion
Eddy current testing is a valuable tool that can be used to detect surface and subsurface defects in metals and other conductive materials. It is a non-destructive method of testing that can save time and money by enabling parts to be inspected and tested without being removed from service or re-manufactured. The versatility of eddy current testing means it can be used in a variety of different inspection techniques and applications, making it a powerful tool for industry and manufacturing.
