1. Eddy Current – An Efficient NDT Testing Method
One of many NDT methods used is eddy current that works on the principal of “electromagnetism”
to conduct examinations. Several other methods like Remote Field Testing (RFT) and Flux Leakage
also work on this principle for evaluating materials.
Eddy currents are created by a process known as electromagnetic induction. When alternating
current is applied to a conductor like copper wire, a magnetic field exists in and around the
conductor. This magnetic field expands with the rise in alternating current and collapses as the
current reduces to zero. When another electric conductor is brought in the vicinity of this changing
magnetic field current is induced in the second field. Eddy currents are induced currents that follow
a circular path. They get their name from the ‘eddies’ which form when a liquid or a gas flows in
a circular path around obstacles under the most appropriate conditions.
There are many advantages of using this technology to perform a variety of measurements and
evaluation. Under proper circumstances, Eddy Current can be used to perform checks like:
 Coating thickness measurements
 Crack detection
 Material thickness measurements

2. It is also used for conductivity measurements for:
 Heat damage detection
 Material identification
 Heat treatment monitoring
 Case depth determination
This easy and efficient testing method has many advantages:
 Detects surface and near surface defects
 Sensitive to small cracks and other defects
 Equipment is easily portable
 Test probe does not need to contact the part
 Scrutinizes complex shapes and sizes of conductive materials
 Method can be used for much more than flaw detection
 Inspection gives immediate results
 Minimum part preparation is required
When using this evaluation method, there are some important factors which must be considered.
Some limitations have to be taken into account:
 Surface finish and roughness may get in the way
 Surface must be accessible to the probe
 Depth of penetration is limited
 Reference standards needed for setup
 Skill and training required is more extensive than other techniques
 Only conductive materials can be inspected
 Some flaws lying parallel to the probe coil winding are undetectable
Industrialists, engineering and many other manufacturing companies rely on different testing
methods to ensure credibility of the materials or processes in question. Aside from Visual Testing
Massachusetts, there are many testing methods which professionals use to bring quality in processes.
Many service providers also offer testing and inspection to help industrialists.
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