PSI - Issue 5

Francisco Barros et al. / Procedia Structural Integrity 5 (2017) 1260–1266 Francisco Barros et al./ Structural Integrity Procedia 00 (2017) 000 – 000

1266

7

The discrepancies between the two methods might also be explained by the filtering and smoothing performed by the commercial software.

4. Conclusion and future work

The results obtained with the frequency domain method match the values computed by commercial software using traditional intensity based DIC calculations. This indicates that the developed method is accurate, at least for small deformations, and could, in the future, be implemented in situations where it would replace traditional methods in cases where they yield low quality results, namely field measurements where a controlled environment with regard to lighting quality is difficult to achieve. The method is still in an early stage of development and is in need of some improvement and further validation before it can be considered fully reliable. It is currently limited to small deformations that do not deviate much from pure translation. It also lacks filtering of points whose 3D position is wrongly detected. The frequency domain method should also be tested in the aforementioned conditions where traditional methods are prone to fail, in order to validate it as a better alternative to these methods. The authors gratefully acknowledge the funding of Project NORTE-01-0145-FEDER-000022 - SciTech - Science and Technology for Competitive and Sustainable Industries, co-financed by Programa Operacional Regional do Norte (NORTE2020) through Fundo Europeu de Desenvolvimento Regional (FEDER). References [1] M. A. Sutton, J. J. Orteu and H. W. Schreier, Image Correlation for Shape, Motion and Deformation Measurements: Basic Concepts, Theory and Applications, Springer, 2009. [2] B. Pan, H. Xie and Z. Wang, “Equivalence of digital image correlation criteria for pattern matching,” Applied Optics, vol. 49, no. 28, pp. 5501-5509, 2010. [3] H. Lu, C. Huang, C. Wang, X. Wang, H. Fu and Z. Chen, “Fast and noninterpollating method for subpixel displacement analysis of digital speckle images using phase shifts of frequency spectra,” Applied Optics, vol. 53, no. 13, pp. 2806-2814, 2014. [4] M. C. M. Wright, Lecture Notes on the Mathematics of Acoustics, Imperial College Press, 2005. [5] K. R. Rao, D. N. Kim and J. J. Hwang, Fast Fourier Trasnform: Algorithms and Applications, New York: Springer, 2010. [6] R. N. Bracewell, The Fourier Transform and its Apllications, 3rd ed., Mc Graw Hill, 2009. [7] M. Guizar- Sicairos, S. T. Thurman and J. R. Fienup, “Efficient subpixel image registration algorithms,” Optics Letters, vol. 33, no. 2, pp. 156-158, 2008. [8] R. Soummer, L. Pueyo, A. Siv aramakrishnan and R. J. Vanderbei, “Fast computation of Lyot -style coronagraph propagation,” Optics Express, vol. 15, no. 24, pp. 15935-15951, 2007. Acknowledgements