How is the characteristic frequency (fg) calculated in an impedance diagram for a solid nonmagnetic rod?

The characteristic frequency (fg) in the context of an impedance diagram for a solid nonmagnetic rod is related to the material properties and the dimensions of the rod. The correct formula reflects the relationship between the conductivity and the magnetic permeability of the material, as well as the dimensions of the rod.

In this case, fg = 5060 / σµ / d^2 is the expression that properly relates these parameters under the circumstances of Eddy Current Testing. The coefficient 5060 serves as a constant that is derived from the context of the specific system being analyzed, considering factors such as the dimensions in millimeters and the units of conductivity. The presence of σ (conductivity) and µ (permeability) in the denominator indicates that as conductivity increases, the characteristic frequency decreases, while a higher magnetic permeability may influence the eddy current flow as depth and frequency change.

This particular formulation encapsulates the necessary relationship between the physical dimensions of the material, its electromagnetic characteristics, and how they influence the eddy current responses in the testing methodology. Understanding this relationship helps in interpreting the results of the impedance diagram in practical applications of Eddy Current Testing.