Skin Effect
Skin effect is the phenomenon where high-frequency alternating currents preferentially flow in the near-surface layers of a conductor. This limits the testing depth in eddy current testing.
Physicochemical Mechanism of Action
High-frequency alternating currents induce a magnetic flux density in metals that is enhanced in the surface layers. This leads to increased electrical resistance in these layers, which affects the current flow profile and reduces thermal conductivity.
Metallurgical Relevance & Risks in Welding
The skin effect limits the inspection depth in the eddy current method, as the heat input occurs mainly in the near-surface layers. This can lead to inaccurate test results and increase the risk of defects.
Workshop Practice & Action Instructions
To minimize the skin effect, use metals with low thermal conductivity when eddy current testing or increase the frequency of the alternating current. Pay attention to a correct control design depth and carry out regular calibrations.