Which property of a material can decrease the effectiveness of eddy current testing?

The effectiveness of eddy current testing is influenced by various material properties, and increased thickness is a significant factor. Eddy current testing is based on the principles of electromagnetic induction, where an alternating current generates a magnetic field that induces eddy currents in the material being tested. However, as the thickness of the material increases, the depth of penetration for the induced eddy currents decreases. This is known as the skin effect, where the eddy currents tend to flow more in the surface layer of the material rather than penetrating deeply.

When a material is thicker, the eddy currents may not reach deeper flaws or anomalies located within the material, potentially leading to missed defects or inadequate evaluations of material integrity. Therefore, increased thickness can hinder the ability of eddy current testing to effectively inspect the material and detect subsurface defects.

Understanding how material thickness impacts the performance of eddy current testing is crucial for ASNT Level II technicians, as they need to assess whether the testing method is suitable given the specific characteristics of the material being inspected.