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

Conference · Thu Apr 01 04:00:00 EST 1993

OSTI ID:10180562

Del Grande, N K; Dolan, K W; Durbin, P F; Gorvad, M R; Kornblum, B T; Perkins, D E; Schneberk, D J; Shapiro, A B

We discuss three-dimensional (3D) dynamic thermal imaging of structure 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. We use a DBIR imaging unique pioneered at LLNL to capture the time history of surface temperature difference for flash-heated targets. We relate these patterns to the location, size, shape and depth of subsurface flaws. We have demonstrated temperature accuracies of 0.2{degree}C, timing synchronizations of 3 ms (after onset of heat flash) and intervals of 42 ms, between images, during an 8 s cooling (and hearing) interval characterizing the front (and back) surface temperature-time history of an epoxy-glue disbond site in a flash-heated aluminum lap joint. This type of disbond played a significant role in causing damage to the Aloha Aircraft fuselage on the aged Boeing 737 jetliner. By ratioing DBIR images (near 5 and 10 micron), we located surface temperature patterns (generated by weak heat flow anomalies at subsurface flaw sites) and removed the emissivity mask (from surface roughness variations). We compared measurements with calculations from the three-dimensional, finite element computer code: TOPAZ3D. We combined infrared, ultrasound and x-ray imaging methods to characterize the lap joint disbond site spatial, bond quality, and material differences.

• Research Organization: Lawrence Livermore National Lab., CA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 10180562
• Report Number(s): UCRL-JC--113744; CONF-930445--23; ON: DE93019575
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420200
440600
47 OTHER INSTRUMENTATION
99 GENERAL AND MISCELLANEOUS
990200
AIRCRAFT
ALGORITHMS
ALUMINIUM
EPOXIDES
FACILITIES, EQUIPMENT, AND TECHNIQUES
FINITE ELEMENT METHOD
INFRARED THERMOGRAPHY
MATHEMATICS AND COMPUTERS
OPTICAL INSTRUMENTATION
PHOTON COMPUTED TOMOGRAPHY
T CODES
THERMAL ANALYSIS
THREE-DIMENSIONAL CALCULATIONS