What does the term "phase shift" in eddy current testing refer to?

The term "phase shift" in eddy current testing refers to the lag between input and output signals. In this context, phase shift is an important concept because it provides insight into the characteristics of the material being tested.

When eddy currents are induced in a conductive material, the resulting electromagnetic fields interact with the material's properties, such as conductivity and permeability. This interaction can cause a phase difference between the induced eddy current signal (output signal) and the primary field (input signal). The amount of phase shift is influenced by the material's properties and the presence of any defects, providing valuable information about the material's condition.

The phase shift can be quantified and analyzed to determine various parameters, such as the presence of cracks or corrosion. As such, it serves as a key indicator in the evaluation process during eddy current testing. Understanding this relationship allows technicians to form conclusions about material integrity, enabling effective inspections and assessments.