Monday, July 4, 2011

Brief introduction to Eddy Current Testing, Applications and Limitations

What are Eddy Currents? What is eddy current inspection?

Eddy current inspection is one of several NDT methods that use the principal of electromagnetism” as the basis for conducting examinations. Eddy currents are created through a process called electromagnetic induction. When alternating current is applied to the conductor, such as copper wire, a magnetic field develops in and around the conductor. If another electrical conductor is brought into the close proximity to this changing magnetic field, current will be induced in this second conductor.

 In brief Eddy currents are induced electrical currents that flow in a circular path.

 Where do we used Eddy Currents?
 • Crack detection   
 • Material thickness  measurements 
 • Coating thickness measurements  
 • Conductivity measurements

What are the advantages of Eddy current testing as NDT method?

• Eddy current inspection is an excellent  NDT Method for detecting surface and near surface discontinuities when the probable defect location and orientation is well known. 

• Sensitive to small cracks and other defects

• Inspection gives immediate results

• Equipment is very portable

• Test probe does not need to contact the part

• Inspects complex shapes and sizes of conductive materials

What are the limitations?

• Only conductive materials can be inspected

• Surface must be accessible to the test probe

• Skill and training required is more extensive than other NDT methods

• Depth of penetration is limited