Enhancement of Eddy Current Testing Sizing Capability for Deep Cracks Using Multi-Exciting Coils

In order to enhance sizing capability for a deep crack, a modified multiple exciting coil eddy current testing scheme was proposed and studied. Not only the amplitude, but also the phase of the exciting current in the two pairs(four) of exciting coils were adjusted to suppress the eddy currents on the surface of the inspection target. The numerical results revealed that the modified way could give some improvement of sizing capability for deep cracks.