In an eddy current test, what influences the depth of penetration?

In eddy current testing, the depth of penetration is primarily influenced by the frequency of the test signal. When the frequency increases, the depth of penetration decreases. This is due to the skin effect, which describes how alternating currents tend to flow near the surface of conductors, with deeper penetration occurring at lower frequencies.

As frequency increases, the induced eddy currents are concentrated closer to the surface, reducing the effective depth from which the eddy currents can detect flaws or changes in material properties. Therefore, selecting the appropriate frequency is critical for assessing materials of different thicknesses and properties effectively.

Other factors, such as the type of material being tested, probe geometry, and environmental conditions, do play roles in the overall testing process, but they do not directly affect the depth of penetration as significantly as frequency does.