Edge Effect
The edge effect is the distortion of an eddy current signal as the probe approaches a part edge, hole, or geometric discontinuity, which can mask defect signals near edges.
Definition
Eddy currents distribute differently near a free edge, producing a large signal that can swamp defect indications. Higher frequencies, smaller-diameter probes, or specialized edge probes minimize edge effect.
Related terms
- Lift-Off — Lift-off is the change in eddy current signal caused by a variation in the distance between the probe coil and the test surface, used both as a calibration tool and as a nuisance variable to be minimized.
- Impedance Plane — The impedance plane is a 2D display in eddy current testing showing the probe coil's resistive (X-axis) and inductive reactive (Y-axis) components, on which signals from lift-off, defects, and conductivity changes trace characteristic vectors.
- Eddy Current Testing (ET) — Eddy Current Testing (ET) is an electromagnetic NDT method that induces circulating currents in conductive materials using an AC coil; changes in coil impedance reveal surface and near-surface defects, conductivity variations, and coating thickness.
More physics terms
Back-Wall Echo · Beam Spread · Near-Field · Far-Field · Dead Zone · Shear Wave · Longitudinal Wave · Surface Wave · Lamb Wave · Mode Conversion
Where this comes up in practice
Terms like this one appear in three places that matter commercially: the written practice that governs how your personnel are qualified, the procedures and technique sheets that define how an examination is actually performed, and the evidence an auditor or client asks for when they want to know why an inspection was accepted. Getting the terminology right is the easy part; being able to produce the qualification record, the calibration traceability and the procedure revision that applied on the day of the inspection is the part that decides audits.
Atlantis NDT provides NDT training and certification against ASNT SNT-TC-1A and ISO 9712, ASNT Level III consulting for written practices and procedure approval, inspection management software that holds qualification, calibration and procedure-revision evidence in recoverable form, and an asset integrity platform that binds inspection results to the asset they describe. Browse the full NDT glossary or ask a Level III directly.