How does test frequency affect the depth of penetration for eddy currents?

In eddy current testing, the frequency of the eddy currents directly influences the depth of penetration into the material being tested. As the frequency increases, the skin effect becomes more pronounced. The skin effect refers to the phenomenon where alternating current tends to flow near the surface of a conductor rather than penetrating deeply. Thus, higher frequencies result in a reduced penetration depth.

In contrast, lower frequencies allow for a greater penetration depth, as the currents have a better ability to travel into the material. Therefore, understanding the relationship between frequency and penetration depth is critical for effective eddy current testing, particularly when assessing the condition of materials or detecting flaws. This relationship is essential for technicians to tailor their testing methods based on the specific requirements of the materials they are working with and the types of imperfections they are looking to identify.