Dynamic thermal tomography for nondestructive inspection of aging aircraft

We apply dual-band infrared (DBIR) imaging as a dynamic thermal tomography tool for wide area inspection of a Boeing 737 aircraft (owned by the FAA/AANC at the Sandia hangar in Albuquerque, NM) and several Boeing KC-135 aircraft panels (used for the round robin experiment conducted at Tinker AFB, OK). Our analyses are discussed in this report. After flash-heating the aircraft skin, we record synchronized DBIR images every 40 ms, from onset to 8 seconds after the heat flash. We analyze selective DBIR image ratios which enhance surface temperature contrast and remove surface-emissivity clutter (from dirt, dents, tape, markings, ink, sealants, uneven paint, paint stripper, exposed metal and roughness variations). The Boeing 737 and KC-135 aircraft fuselage panels have varying percent thickness losses from corrosion. We established the correlation of percent thickness loss with surface temperature rise (above ambient) for a partially corroded F-18 wing box structure (with a 2.9 mm uncorroded thickness) and several aluminum plates (with 1.0, 1.1, 2.3, and 3.9 mm thicknesses) which had 6 to 60% thickness losses at milled flat-bottom hole sites.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.