An Eddy Current Testing Probe with Dual-Frequency Excitation to Detect Deep Cracks

The skin effect is a common phenomenon in the eddy current testing (ECT), which can make the eddy currents concentrated near the specimen surface and cannot flow into the material. In order to improve the ability of the eddy current probe to detect the deep defects, a new probe with dual-frequency excitation is proposed, which can suppress the eddy current density near the surface of the specimen. The purpose of identifying deep crack defects in stainless steel specimen is achieved with the probe. In this paper, the ANSYS software is used to determine the frequency, excitation current and coil arrangement of the probe. The ability of the new probe to detect deep cracks is verified by experiments. The results show that the detection signal of the cracks with depth of 10 and 15 mm is 4 times and 4.47 times than that of the crack with 5 mm depth. It is more sensitive to the depth change of deep cracks.