In eddy current testing, what happens if the test frequency is increased?

When the test frequency is increased in eddy current testing, there is an enhancement in sensitivity to surface defects. Higher frequencies lead to the generation of eddy currents that are more concentrated near the surface of the material being tested. This occurs because the skin effect causes the eddy currents to flow primarily within a limited depth from the surface. As a result, small surface defects, such as cracks, corrosion, or other anomalies, are more likely to be detected since their impact on the eddy current response becomes more pronounced at higher frequencies.

The relationship between frequency and detection capability is vital in applications where surface integrity is critical. While this increased sensitivity can improve the overall effectiveness of the test for identifying surface flaws, it also means that deeper defects will be harder to detect, as higher frequencies do not penetrate as deeply into the material. Therefore, the choice effectively underscores the importance of tuning the frequency according to the specific requirements of the inspection being performed.