Small Eddy Current Testing Sensor Probe using Tunneling Magnetoresistance Sensors for Detection of Cracks in Steel Structures

摘要

Eddy current testing (ECT) is a nondestructive testing (NDT) method, and is widely used to detect flaws in metal structures. ECT involves the use of a pair of detection and induction coils. The detection coil is used to measure the secondary magnetic field generated by the eddy current in the metal due to the applied AC magnetic field of the induction coil. In the case of a nonmagnetic material, since the magnetic field detected by the detection coil is generated only by the eddy current, ECT using a detection coil is suitable for detecting any abnormality in the eddy current distribution caused by a flaw. However, in the case of ferromagnetic materials, the magnetic field detected by the detection coil arises not only from the eddy current but also from the magnetization of the material.