What effect does a lower testing frequency have on eddy current penetration?

A lower testing frequency in eddy current testing generally increases the depth of penetration of the current into the material being tested. Eddy currents are generated by the electromagnetic fields induced by the testing probe, and the frequency of the testing directly impacts how deeply these currents can penetrate.

As the frequency decreases, the skin effect, which causes eddy currents to be concentrated near the surface, is reduced. This means that the eddy currents can extend deeper into the material, allowing for better penetration and potentially improving the detection of subsurface defects. This is particularly important in applications where assessing material conditions beneath the surface is crucial.

The other potential effects, although relevant to eddy current testing, do not relate to increasing penetration depth as directly as the chosen answer does. For instance, lower frequency may also lead to decreased defect detection in some scenarios, focusing on surface anomalies rather than deep defects. However, the main aspect to note is the relationship between frequency and penetration depth, where a lower frequency indeed supports deeper eddy current flow into the material.