Dual-band infrared thermography for quantitative nondestructive evaluation
The authors have developed dual-band infrared (DBIR) thermography that is being applied to quantitative nondestructive evaluation (NDE) of aging aircraft. The DBIR technique resolves 0.2 degrees C surface temperature differences for inspecting interior flaws in heated aircraft structures. It locates cracks, corrosion sites, disbonds or delaminations in metallic laps and composite patches. By removing clutter from surface roughness effects, the authors clarify interpretation of subsurface flaws. To accomplish this, the authors ratio images recorded at two infrared bands, centered near 5 microns and 10 microns. These image ratios are used to decouple temperature patterns associated with interior flaw sites from spatially varying surface emissivity noise. They also discuss three-dimensional (3D) dynamic thermal imaging of structural flaws using dual-band infrared (DBIR) computed tomography. Conventional thermography provides single-band infrared images which are difficult to interpret. Standard procedures yield imprecise (or qualitative) information about subsurface flaw sites which are typically masked by surface clutter. They use a DBIR imaging technique pioneered at LLNL to capture the time history of surface temperature difference patterns for flash-heated targets. They relate these patterns to the location, size, shape and depth of subsurface flaws. They have demonstrated temperature accuracies of 0.2{degree}C, timing synchronization of 3 ms (after onset of heat flash) and intervals of 42 ms, between images, during an 8 s cooling (and heating) interval characterizing the front (and back) surface temperature-time history of an epoxy-glue disbond site in a flash-heated aluminum lap joint.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States); Federal Aviation Administration, Washington, DC (United States); Department of Defense, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 10181259
- Report Number(s):
- UCRL-JC-113742; CONF-9304189-3; ON: DE93019151; TRN: AHC29311%%17
- Resource Relation:
- Conference: 1993 joint Army, Navy, NASA, Air Force (JANNAF) nondestructive evaluation subcommittee meeting,Livermore, CA (United States),26-28 Apr 1993; Other Information: PBD: Apr 1993
- Country of Publication:
- United States
- Language:
- English
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