Analytical Model of an I-Core Coil Inspecting a Metal Disk With a Borehole and an Annular Slot

The impedance variation of an I-core coil above a metal disk with a borehole and an annular slot is analyzed by an enhanced truncated region eigenfunction expansion (TREE) method. This problem is intractable by the conventional TREE method, mainly due to the numerical overflow of eigenfunctions of the air-metal multisubdomain regions. By the improved TREE without the deficiency of overflow, an accurate and efficient analytical solution is successfully obtained. Numerical and experimental verification of the proposed method is provided. Satisfactory agreement is achieved, and the efficiency of the propounded method is also confirmed.