What term defines an eddy current test coil that uses magnetic material to shape the magnetic field?

The term that defines an eddy current test coil using magnetic material to shape the magnetic field is "Gap coil." In this context, a gap coil is designed to concentrate the magnetic field into a specific area, enhancing the sensitivity of the eddy current testing process. This feature is particularly beneficial for detecting surface and near-surface defects in magnetic materials, as the shaping of the magnetic field allows for better interaction with the conductive material being tested.

The construction of gap coils typically incorporates magnetic materials, which helps in focusing the magnetic flux lines and improving detection capabilities. This design can be applied effectively in various critical applications, such as identifying cracks or other anomalies that may compromise the integrity of components.

In contrast, other types of coils like bobbin coils, encircling coils, and spinning coils serve different purposes or operate under different principles. Bobbin coils are often used for measuring the conductivity of cylindrical samples, encircling coils are utilized for inspecting larger flat parts, and spinning coils are typically employed for dynamic testing on rotating components. Each coil type has its own unique attributes depending on the specific application in eddy current testing.