Relationship Between the Eddy Current Probe Size and the Flaw Size for Flaw Detection: A Numerical Study

The flaws of metal parts can seriously harm the safety of operating equipment. Eddy current testing (ECT) is a common technique based on the electromagnetic induction principle for non-destructive testing of mental specimens. The eddy current probe size and the flaw size are two sensitive parameters affecting the detection performance. Present researchers analyze them separately while the relationship between them is also worth exploring. In this work, a two-dimensional finite element model (FEM) for eddy current testing is established to study the relationship between the eddy current probe size and the flaw size. The size of the probe is optimized by taking the inner and outer diameter of the probe as the change factor. This research has found that probe with smaller sizes has higher sensitivity and better linearity. In addition, the variation regularity of coil impedance signal waveform in the process of the probe scanning for flaws is revealed, and the corresponding explanation is given from the perspective of energy change. It is also found that the distance between inflection points can be extracted from the real or imaginary part of the impedance curve to quantify the flaw length.