In the decade since the first production Shearography NDT system was implemented on the Northrop B-2 Stealth Bomber program, laser shearography has evolved into a very powerful and respected tool for the rapid inspection of composite aerospace structures. Shearography images deformation derivatives of a structure subjected to a differential stress. These images reveal delaminations, impact damage, core splices, skin-to-core disbonds and in many cases allow the detection and measurement of defects located on the far side. Recent advances in phase stepping shearography show more than an order of magnitude increase in sensitivity to defects in composites. In the last two years shearography systems have become available which are highly competitive with Ultrasonic C-Scan and offer substantial improvement in through-put, productivity and cost-benefit. In addition, portable on-aircraft shearography systems are now being used by airlines, aircraft manufacturers and military aircraft maintenance facilities for a wide range of large area inspection applications. This paper will focus on the basic theory of shearography nondestructive testing, defect detection capabilities and probability of detection as a function of material and design. In addition, we will examine four case studies where shearography NDT has been selected for major aerospace programs.
Publication Source: Trends in NDE Science & Technology; Proceedings of the 14th World Conference on Non-Destructive Testing, New Delhi, 8-13 December 1996.full paper not received Publisher:Ashgate Publishing Company
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