In Eddy Current Testing, what does a phase shift typically indicate?

In Eddy Current Testing, a phase shift is a significant indicator of changes in impedance related to defects within the material being tested. When eddy currents are induced in a conductor, they generate a magnetic field that interacts with the material properties. If a defect, such as a crack, corrosion, or other discontinuity, is present, it affects the distribution of eddy currents and consequently modifies the impedance.

As defects alter the path and density of the induced currents, the relationship between the voltage and the current (which is known as the phase angle) changes. This phase shift is directly correlated with the type and extent of the defect, allowing inspectors to characterize the nature of the flaw and assess its impact on the material's integrity.

Understanding this relationship is crucial for accurately interpreting test results and determining the condition of the material, which is why a phase shift is primarily associated with changes in impedance due to defects.