Non destructive testing is an important application in the production of safety critical components and the maintenance thereof. Digital Shearography is an emerging NDT technique, particularly suited for the detection of defects within composite structures as found for example in the aircraft and aerospace industries. This paper presents the initial results of a project aimed at developing a low cost portable NDT prototype based an the principles of digital Shearography. As part of the cost saving measures the system is designed to operate off a laptop using a FireWire interface. The developed test unit achieved a significant cost reduction, in the order of 50 %, by using lower cost components where available, a higher level of OEM integration, and customwritten software. Its performance was satisfactory, acquiring conventional intensity-based and phase-stepped interference images which were used to successfully detect flaws in two different aerospace components. The phase-stepped images that were obtained were of sufficient quality to be filtered and phase-unwrapped to reveal the surface displacements. In comparison to the existing shearography implementation, the new testing unit produced images that are of a slightly lower quality, particularly in conventional intensitybased shearography. The FireWire camera exhibits a poorer signal to noise ratio and appears to be less sensitive than the CameraLink version used in the prior prototype. It was also noted that the repeatability of the phase stepping module, if used over an extended period of time, needs to be investigated, as a minimal amount drift in the preset PZT steps was noted. The impact of these two aspects is marginal though, as the unit produced perfectly usable results.
Evaluating low cost portable shearography on aircraft components
Bewertung einer preiswerten transportablen Scherographie an Luftfahrtkomponenten
2008
9 Seiten, 10 Bilder, 6 Quellen
Conference paper
English
Evaluating Low Cost Portable Shearography on Aircraft Components
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