Three-dimensional dynamic thermal imaging of structural flaws by dual-band infrared computed tomography

Nancy DelGrande; Kenneth W. Dolan; Philip F. Durbin; Michael R. Gorvad; B. T. Kornblum; Dwight E. Perkins; Daniel J. Schneberk; Arthur B. Shapiro

doi:10.1117/12.160340

15 November 1993 Three-dimensional dynamic thermal imaging of structural flaws by dual-band infrared computed tomography

Nancy DelGrande, Kenneth W. Dolan, Philip F. Durbin, Michael R. Gorvad, B. T. Kornblum, Dwight E. Perkins, Daniel J. Schneberk, Arthur B. Shapiro

Author Affiliations +

Proceedings Volume 1942, Underground and Obscured Object Imaging and Detection; (1993) https://doi.org/10.1117/12.160340
Event: Optical Engineering and Photonics in Aerospace Sensing, 1993, Orlando, FL, United States

Abstract

We discuss three-dimensional dynamic thermal imaging of structural flaws using dual-band infrared (DBIR) computed tomography. Conventional (single-band) thermal imaging is difficult to interpret. It yields imprecise or qualitative information (e.g., when subsurface flaws produce weak heat flow anomalies masked by surface clutter). We use the DBIR imaging technique to clarify interpretation. We capture the time history of surface temperature difference patterns at the epoxy-glue disbond site of a flash-heated lap joint. This type of flawed structure played a significant role in causing damage to the Aloha Aircraft fuselage on the aged Boeing 737 jetliner. The magnitude of surface-temperature differences versus time for 0.1 mm air layer compared to 0.1 mm glue layer, varies from 0.2 to 1.6 degree(s)C, for simultaneously scanned front and back surfaces. The scans are taken every 42 ms from 0 to 8 s after the heat flash. By ratioing 3 - 5 micrometers and 8 - 12 micrometers DBIR images, we located surface temperature patterns from weak heat flow anomalies at the disbond site and remove the emissivity mask from surface paint of roughness variations. Measurements compare well with calculations based on TOPAX3D, a three-dimensional, finite element computer model. We combine infrared, ultrasound and x-ray imaging methods to study heat transfer, bond quality and material differences associated with the lap joint disbond site.

Citation Download Citation

Nancy DelGrande, Kenneth W. Dolan, Philip F. Durbin, Michael R. Gorvad, B. T. Kornblum, Dwight E. Perkins, Daniel J. Schneberk, and Arthur B. Shapiro "Three-dimensional dynamic thermal imaging of structural flaws by dual-band infrared computed tomography", Proc. SPIE 1942, Underground and Obscured Object Imaging and Detection, (15 November 1993); https://doi.org/10.1117/12.160340

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