SBIR-STTR Award

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

Nondestructive inspection is a key component of programs aimed at extending the service life of aging aircraft. One important capability is the detection of cracking and corrosion around fastener holes. In thick, multiple layer structures, there is often no solution but removal of the fasteners for inspection, a costly and potentially damaging process. Phased array ultrasonics offer a novel and powerful solution. In Phase I of this project, we have demonstrated the technical feasibility of phased arrays for inspection without fastener removal through experimental measurements on two-layer specimens and through the design of a prototype. The validity of the design was demonstrated by extensive ray-tracing and ultrasonic field modeling studies. In Phase II our focus is building and testing the prototype. If we are successful, we anticipate Phase III funding to adapt our device to specific Air Force aircraft, which we intend to accomplish with the help of our large commercial partners.

Keywords:
Fastener, Phased Array, Crack, Detection, Inspection, Ultrasonic, Nondestructive