Thermal Wave Imaging for NDI of Aircraft

We describe the application of Pulse-echo thermal wave imaging to nondestructive inspection [NDI] of aircraft. This technique uses high-power photographic flash lamps as a heat source and an IR video camera as a detector. The flash lamps launch pulses of heat into the skin of the aircraft and the IR camera images the returning thermal wave reflections from subsurface defects. The system also includes electronic hardware and software for carrying out the time-gated imaging and real time analysis of the defects. It also has the ability to image large areas (currently 17” wide by 17” high) in short times (currently one minute, including time to store the image and move the system to the adjacent imaging position). This translates into an inspection speed of over 90 feet of a 17” strip of aircraft per hour. We have applied the technique to a variety of airframe defects, including metal and composite structures. Images of typical structures and defects are presented.