Measuring the defect size of a rectangular metallic plate with finite size based on sweep-frequency eddy current testing

Eddy current testing can accurately assess the size, shape and location of defects within the material by virtue of its high-precision detection capability, which effectively guarantees the safety and reliability of equipment operation and reduces the risk of accidents. This paper developed a method of eddy current testing (ECT) for estimating the size of the through-hole defect in the rectangle metallic plate with finite size. Specifically, a modified analytical solution method is investigated for rectangle metallic plates with rectangular through-holes. The integration bounds are modified to the values associated with the polar angle and the hole dimensions of the metallic plate. In addition, the size measurement problem regarding the hole is transformed into a least-squares problem, and an improved Newton–Raphson iterative solver is investigated to reconstruct the size of the through-hole defect. Both numerical solutions and experiments are conducted to verify the proposed method. The size of the through-hole defect can be accurately determined by a modified analytical solution and an iterative solver. Related experimental results indicate that the estimation error of defect size is only 3.7%.