Correlation of eddy current signals obtained from EDM notches and fatigue cracks

For calibration of eddy current testing, artificial defects are commonly used by virtue of its simple production and ease control of geometric parameters. However, such defects are significantly different in terms of geometric aspects from real ones, even with a precise control of the manufacturing process. To ensure reliable calibration results, it is mandatory to establish a relationship between the signals from artificial (machined) and real defects. This work exposes a detailed study correlating eddy current signals from electrical discharge machine notch (EDM notch) and fatigue cracks. To perform the tests an absolute pencil probe was used. Although there is a significant difference between the signals of EDM notch and fatigue cracks, the results show that it is possible to use artificial defects to represent fatigue cracks reliably if a proper correction is implemented.