Quantitative thermal depth imaging of subsurface damage in insulating materials

K. Elliott Cramer; Patricia A. Howell; William P. Winfree

doi:10.1117/12.141968

6 April 1993 Quantitative thermal depth imaging of subsurface damage in insulating materials

K. Elliott Cramer, Patricia A. Howell, William P. Winfree

Proceedings Volume 1933, Thermosense XV: An International Conference on Thermal Sensing and Imaging Diagnostic Applications; (1993) https://doi.org/10.1117/12.141968
Event: Optical Engineering and Photonics in Aerospace Sensing, 1993, Orlando, FL, United States

Abstract

A thermal technique is presented for imaging subsurface damage and computing the depth of damaged areas for low diffusivity materials. The measurement technique presented uses uniform heating with quartz lamps over a large area. The surface temperature of the sample is collected using a scanning IR radiometer and a real time image processor during the cooling of the sample after heating. Flaw depths are computed by performing a numeric approximation to the surface Laplacian on each temperature image in the time series. The depth of the damage is then calculated from the time required for the amplitude of the surface Laplacian to reach a minimum in the region over the damage. Experimental results from the application of the technique to low diffusivity materials with surface and subsurface defects at various depths are presented showing the technique's ability to give quantitative depth of damage information. Additionally, the effects of variations in defect size on the time for flux minimum, and thus on the calculated depth, is also investigated. Finally, finite element simulations are compared with experimental results.

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K. Elliott Cramer, Patricia A. Howell, and William P. Winfree "Quantitative thermal depth imaging of subsurface damage in insulating materials", Proc. SPIE 1933, Thermosense XV: An International Conference on Thermal Sensing and Imaging Diagnostic Applications, (6 April 1993); https://doi.org/10.1117/12.141968

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Thermography

Image processing

Radiometry

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Video processing

Data acquisition

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