Meaning
Electromagnetic induction methods detect surface or near-surface flaws in conductive materials without damaging the component. Eddy current non destructive testing relies on a probe that generates an alternating magnetic field to induce circular currents in the test piece. Variations in the electrical conductivity or magnetic permeability of the material indicate the presence of cracks or voids.
Surface Detection
High frequency signals concentrate the induction near the exterior of the part. This surface detection mode in eddy current non destructive testing is ideal for finding fatigue cracks in aluminum skins or thin walled tubing.
Signal Interpretation
Inspectors monitor the phase and amplitude of the impedance change on an oscilloscope to identify specific defect types. Because eddy current non destructive testing is sensitive to both geometry and material properties, the operator must distinguish between a genuine flaw and a change in the alloy composition. Modern digital filters help isolate the signal from background noise and heat treatment effects.
Material Limit
Conductivity variations across different batches of metal can skew the results if the instrument is not regularly zeroed. While eddy current non destructive testing is effective for non-ferrous alloys, the strong magnetic properties of carbon steel often require specialized probes to achieve deep penetration. Correct calibration against a known standard is the only way to ensure the reliability of the inspection.
