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Various methods are widely used for the detection of surface defects. Among these methods, the eddy current testing (ECT) method, stands out the most. The eddy current method is based on the principle of electromagnetic induction. It is used to identify or distinguish a wide variety of physical, structural and metallurgical properties of conductive materials. Since electromagnetic energy is used in the method, there is no need for direct contact with the inspected element. These changes will be amplified and will be represented on a graph.
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Advantages
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Principles
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Penetration depth
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Industrial applications: Rotating probes
- Applied with or without contact between the induction coil and material (i.e. painted conductive materials).
- Anomalies generated by the circulation of the currents are detected by electronic means.
- Repetitiveness: once the systems are properly set up, the repetitiveness is terrific.
- Sensitiveness: the eddy current systems can detect surface defects up to 0,03mm
- Recognized method for most of the standards and codes
- Repetitiveness
- Reliability
- Can be easyly adopted
- Low cost
- Doesn't need human extensive participation
- An alternating current is circulated on a coil and the current is placed closely to the surface of a conductive material. The magnetic field generated in the coil in turn induces a magnetic field in the material.
- The magnetic field induced in the material induces a superficial electric current in the material.
- An analysis of the behaviour of this superficial current with sophisticated electronic equipment can determine the presence and nature of surface defects produced by alterations in the induced current.
- The main applications of this method are the detection of surface discontinuities, the determination of changes from thermal treatments (changes in electrical conductivity), hardness, and the inspection of the welds on welded pipes.
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