What technique is used to increase sensitivity in Eddy Current Testing for surface defects?

Choosing higher frequencies is a technique used to increase sensitivity in Eddy Current Testing for surface defects because higher frequencies generate eddy currents that penetrate less deep into the material. This is advantageous for detecting surface-breaking defects since it allows the testing system to be more responsive to changes in the electromagnetic field caused by flaws closer to the surface.

Eddy current testing operates on the principle that the eddy currents induced in a conductive material will change in response to any discontinuities. When a higher frequency is applied, the induced currents are limited to a smaller depth, enhancing the system's ability to detect small, shallow defects. This increased sensitivity is particularly useful for applications where surface integrity is critical, such as in aerospace or automotive components where surface cracks can lead to catastrophic failures.

While using a larger probe coil or adopting complex geometries may have their benefits in certain contexts, they don't inherently increase sensitivity to surface defects like higher frequencies do. Similarly, applying a pulsed magnetic field is not typical in conventional Eddy Current Testing, which relies on continuous waveforms to induce eddy currents in the material.