AWS Certified Welding Inspector — FundamentalsNondestructive Examination (NDE)Medium
A technician is performing an eddy current testing (ET) inspection on an aerospace component for surface cracks. The probe is a surface coil operating at a specific frequency. What fundamental principle governs the interaction between the eddy current probe and the conductive material to detect discontinuities?
- AThe disruption of induced eddy currents by material discontinuities.
- BThe reflection of sound waves from internal interfaces.
- CThe change in magnetic flux leakage around a discontinuity.
- DThe absorption of radiation by denser materials.
Show answer & explanationAnswer & explanation
Correct answer: A. The disruption of induced eddy currents by material discontinuities.
Eddy current testing operates on the principle of electromagnetic induction. An alternating current in the probe coil generates a primary magnetic field, which induces eddy currents in the test material. Discontinuities or changes in material properties disrupt these eddy currents, causing a detectable change in the impedance of the probe coil.
Why the other options are wrong
- B. This describes the principle of Ultrasonic Testing (UT).
- C. This describes the principle of Magnetic Particle Testing (MT).
- D. This describes the principle of Radiographic Testing (RT).
ET - Operating Principle
Eddy Current Testing (ET) detects discontinuities and material variations by measuring changes in the impedance of a probe coil as induced eddy currents in a conductive material are disrupted by flaws or property changes.
- Based on electromagnetic induction.
- Alternating current in probe induces eddy currents.
- Discontinuities disrupt eddy current flow.
- Disruption changes probe coil impedance.
Memory trick: Each NDE has its own physics trick.