Detection of flaws and defects using lateral migration X-ray radiography

摘要

A new Compton X-ray backscatter imaging (CBI) technique called lateral migration radiography (LMR) is applied to detecting a class of sub-surface defects in materials and structures of industrial importance. Examples are delamination in layered composite structures, delects in deposited coatings on metal surfaces such as in aircraft jet engine components and geometrical structural/composition changes (e.g. due to corrosion) on the inside of shell-like components with only outside surface area access. LMR scans on aircraft samples showed intensity decreases of up to 25 % in corroded areas relative to intensities in clean areas. Especially significant were scans of samples that were performed with the clean or uncorroded side facing up. The corrosion on the opposite side of these 2 mm thick samples, where there was contact between the frame member and the aircraft skin, was clearly visible. Scans of other samples showed that LMR is capable of detecting small flaws on the inside of shell-like components with only outside surface area access. Cracks around a fastener hole that were ～15 mm in length and no more than 0.25 mm in width were seen through the aircraft skin. Scans of an aluminum honeycomb structure demonstrated that LMR is also capable of picking up internal defects that include crushed core and debonding zones.