The Load (Lock) Slot viewed from the top is shaped like a running track around a soccer field (see Figure 1.1). The minimum size of the crack required to be detected is 0.005″×0.010″. For modeling cracks, there are altogether 9 notches in the Slots as marked in the Figure 1.1. The minimum notch at the 9th stage is 0.005″×0.010″. For inspection of this complex geometry, an eddy current probe with a double reflection coil was developed. Scanning occurs in the minor elliptical axis direction while indexing takes place along the major axis. The split of the coil is perpendicular to the scan direction (or in another word, parallel to the Slot edge). The challenge here is the changing scan surface length due to the elliptic shape and the small size (the minor axis is about 1/8″ long) of the inspection area.
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