EXPLOITING GUIDED WAVES FOR MATERIALS CHARACTERIZATION IN PLATES
D. E. Chimenti, O. I. Lobkis, and A. Safaeinili Center for NDE and Dept. of Aerospace Engineering and Engineering Mechanics, Iowa State University, Ames IA 50011
Keywords: Modeling, Algorithm, Material characterization, Guided Waves, NDT
ABSTRACT
A 3-dimensional model has been exploited to construct an efficient inversion algorithm for material characterization. The inversion has been carried out using either wideband or narrow band measurements. Our method utilizes a model that accurately accounts for all geometric and frequency-dependent effects of the experimental setup, enabling us to estimate the viscoelastic material properties and/or sample thickness with a high degree of certainty. The model is based on Auld's reciprocity representation, where the integral of the receiver voltage is evaluated asymptotically, providing an accurate but very efficient signal estimate. Efficiency is crucial in an inversion process where many forward calculations are needed. Wideband measurements have been carried out using swept frequency toneburt chirps, or impulse excitation. This estimation technique has been applied to both isotropic and anisotropic single and/or multilayered plate with excellent results. To achieve narrowband inversion, signals we recorded at many transducer separations. In both cases data were accummulated at multiple incident angles. Good repeatability is found in successive inversions using different measurements. Results are presented both for gas and fluid-coupled conditions.
Publication Source: Trends in NDE Science & Technology; Proceedings of the 14th World Conference on Non-Destructive Testing, New Delhi, 8-13 December 1996.Vol. 1, pages 237 - 240 Publisher:Ashgate Publishing Company
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