Thermographic imaging of cracks in thin metal sheets

K. Elliott Cramer; William P. Winfree; Patricia A. Howell; Hazari I. Syed; Keith A. Renouard

doi:10.1117/12.58532

1 April 1992 Thermographic imaging of cracks in thin metal sheets

K. Elliott Cramer, William P. Winfree, Patricia A. Howell, Hazari I. Syed, Keith A. Renouard

Proceedings Volume 1682, Thermosense XIV: An Intl Conf on Thermal Sensing and Imaging Diagnostic Applications; (1992) https://doi.org/10.1117/12.58532
Event: Aerospace Sensing, 1992, Orlando, FL, United States

Abstract

The presence of cracks significantly decreases the structural integrity of thin metal sheets used in aerospace applications. Thermographic detection of surface temperature variations due to these cracks is possible after external heating. An approximate line source of heat is used to produce an inplane flow of heat in the sheet. A crack in the sheet perturbs the inplane flow of heat and can be seen in an image of the surface temperature of the sheet. An effective technique for locating these perturbations is presented which reduces the surface temperature image to an image of variations in the inplane heat flow. This technique is shown to greatly increase the detectability of the cracks. This thermographic method has advantages over other techniques in that it is able to remotely inspect a large area in a short period of time. The effectiveness of this technique depends on the shape, position and orientation of the heat source with respect to the cracks as well as the extent to which the crack perturbs the surface heat flow. The relationship between these parameters and the variation in the heat flow is determined both by experimental and computational techniques. Experimental data is presented for through-the-thickness, subsurface and surface EDM notches. Data for through-the-thickness fatigue cracks are also presented.

Citation Download Citation

K. Elliott Cramer, William P. Winfree, Patricia A. Howell, Hazari I. Syed, and Keith A. Renouard "Thermographic imaging of cracks in thin metal sheets", Proc. SPIE 1682, Thermosense XIV: An Intl Conf on Thermal Sensing and Imaging Diagnostic Applications, (1 April 1992); https://doi.org/10.1117/12.58532

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