Phased Array Ultrasonic Inspection of Fastener Holes in Two-Layer Structures

"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 oftenno 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 arraysfor 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 PhaseII 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."