Budgetary constraints on defense spending have highlighted the importance of programs aimed at extending the service life of aging aircraft. Nondestructive inspection is a key component of such programs. One important capability is the detection of cracking and corrosion around fastener holes. Phased array ultrasonics offer a novel and powerful solution. They can steer an ultrasonic beam at various angles around the hole, allowing a range of skin thicknesses and fastener diameters to be inspected without mechanical adjustments. Complete circumferential scans can be performed, in some cases without any physical motion of the probe. The added flexibility of examining flaws at a whole range of angles simultaneously leads to a higher probability of detection. The elimination of some or all physical motion reduces weight, size and complexity. The feasibility of detecting first layer corner cracks on the faying surface using phased arrays has been demonstrated in a prior USAF program. Similar technology could be applied to the detection of cracks in multiple layer structures provided sealant exists between the layers to ensure coupling. This proposal outlines our approach for overcoming the technical hurdles of applying phased arrays to thick, multiple layer structures.
Benefits: It is anticipated that technology developed under this SBIR will have direct benefits for United States Air Force Aging Aircraft Programs by allowing safe, rapid and effective nondestructive inspection of fastener holes in thick, multiple layer structures and that such technology, if proven successul, would be acquired by the DoD. As the cost of the technology decreases, it is believed that commercial carriers may also develop an interest
Keywords: fastener, inspection, ultrasonic, phased array, crack, nondestructive, detection
