Fundamental experiments of eddy current testing for additive manufacturing metallic material toward in-process inspection

We evaluated the detectability of the eddy current testing for the inner defects of the additive manufacturing specimens with the step and the slope on the surfaces by the fundamental experiments. The eddy current testing was able to detect the inner defects of 0.5 mm or more in diameter which were at the depth of 0.5 mm from the surfaces of the specimens in signal-to-noise ratio of 2 or more at the frequency of 250 kHz. We also confirmed that the signal post-processing for the acquired eddy current testing data had the potential to separate the inner defect signals from the noises caused by the surface shapes using the difference in the phase angle between the signals and the noises.