An experimental research dealing with the development of novel, infrared interferometers for detecting subsurface disbonds and failure characterization in aerospace materials is undertaken. A real-time, full-field, non-contacting infrared Twyann-Green interferometer using coherent 10.6 micrometer radiation for performing quantitative deformation field mapping has been developed. The choice of the wave length offers the advantage of using the interferometer with structural components with little or no surface preparation of the medium under investigation. The limitation on the surface roughness/texture commonly encountered when using visible light is circumvented through a favourable roughness to wave length ratio in the proposed interferometer. This provides greater latitude in working with surfaces in as-is' condition and in tolerating textural changes that may be due to damage accumulation, plastic deformation and oxidation during testing. The infrared technique provides real-time measurements unlike traditional double exposure schemes involving laser speckels. In this paper, the range of surface roughness which can be studied using this interferometer is reported. Examples of defect detection as well as deformation field quantification for failure characterization are provided.
Publication Source: Trends in NDE Science & Technology; Proceedings of the 14th World Conference on Non-Destructive Testing, New Delhi, 8-13 December 1996.Vol. 5, pages 57 - 58 Publisher:Ashgate Publishing Company
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