新∞コイル型渦電流センサに関する研究

Eddy current testing (ECT) is one of the most representative nondestructive testing methods for metallic materials, parts, structures and so on. Operating principle of ECT is based on two major properties of the magnetic field. One is that alternating magnetic field induces eddy current in conducting materials. Thereby, an input impedance of the magnetic field source, i.e., electric source, depends on the eddy current path. Second is that the magnetic field distribution depends not only on the exciting but also on the reactive magnetic fields caused by the eddy currents in targets. Former and latter are the impedance sensing and magnetic flux sensing types, respectively.This paper concerns with an optimization of a new magnetic flux sensing type sensor named “∞ coil”. Exciting and sensing coils are composed of ∞ shape coil and a finite length solenoid coil wound on ferrite bar, respectively. Development of this ∞ coil fully depends on the 2D and 3D finite elements method modeling. According to the simulation results, we have worked out two types of ∞ coils. Practical experiments reflect the validity of both simulation and design aims, quite well. Thus, we have succeeded in developing ∞ coil having a higher sensibility compared with that of conventional one.