Infrared detection of fatigue cracks and other near-surface defects.

This paper describes a noncontacting, nondestructive inspection system that can rapidly locate, in real time, the position and extent of fatigue cracks in aircraft and missile structures. The automated ir system described was developed for the USAF for use in their Sonic Test Facility at Wright-Patterson AFB. This facility is capable of subjecting large aircraft or missile structures to the intense sound fields experienced in actual flight or launch. In addition to presenting the basic concepts of the method, this paper (1) describes briefly the design of the system that was developed for the USAF, (2) discusses test results, and (3) presents conclusions and indicates future applications of the technique.