With respect to the current issue of ASNT's "The NDT Technician" (JAN2010), there is an article titled "New Inspection Technology Heats Things Up" by Lisa Brasche and Dr. Stephen Holland (both from Center for NonDestructive Evaluation), describing an old method (1970's tech) making a comeback due to advances in IR detection.

In short, vibrothermography (or sonic infrared or thermal acoustics) relies on IR detection of frictional heat when two crack faces are rubbed together.

I thought this was very cool and thought I'd share it with you.

Please reference these links:

http://thermal.cnde.iastate.edu/

http://thermal.cnde.iastate.edu/research.html 

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Most detailed:  http://thermal.cnde.iastate.edu/papers/sonicir_qnde06_published.pdf 

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