Abstract
Many multiaxial experimental setups rely on stereocorrelation (SC) techniques to resolve surface strains and deformations. Torsional loadings can affect the quality and accuracy of SC results due to changes in lighting conditions and the non-conservation of gray levels with the angle of twist. In this note, the gray level correction method implemented for 2D DIC cases is introduced in a 3D surface NURBS SC formalism and applied for torsional loadings. In particular, tension-torsion loading of AISI 1144 steel rods is used to demonstrate the approach. Different surface parameterizations, with and without gray level corrections, are tested in order to enhance the SC quality (defined via gray level residuals). It is found that both gray level corrections and relaxing the regularization of an overly constrained NURBS surface definition (6 vs. 36 knots), lower SC residuals.
References
Beaubier B, Dufour JE, Hild F, Roux S, Lavernhe S, Lavernhe-Taillard K (2014) CAD-Based calibration and shape measurement with stereo-DIC. Exp Mech 54(3):329–341
Dufour JE, Beaubier B, Hild F, Roux S (2015) CAD-based displacement measurements with Stereo-DIC. Exp Mech 55:1657–1668
Piegl L, Tiller W (1997) The NURBS Book, Monographs in Visual Communication, 2nd edn. Springer, Berlin
ASTM E8/E8M - 11 Standard Test Methods for Tension Testing of Metallic Materials, ASTM International
Charbal A, Dufour J-E, Guery A, Hild F, Roux S, Vincent L, Poncelet M (2016) Integrated digital image correlation considering gray level and blur variations: application to distortion measurements of IR camera. Opt Lasers Eng 78:75–85
Acknowledgements
This material is based, in part, upon work supported by the Air Force Office of Scientific Research (AFOSR) under award number FA9550-16-1-0438.
Author information
Authors and Affiliations
Corresponding author
Additional information
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Charbal, A., Cinoglu, I.S., Hild, F. et al. Stereocorrelation Formalism Considering Brightness and Contrast Effects: Application to Torsional Loadings. Exp Mech 60, 727–732 (2020). https://doi.org/10.1007/s11340-019-00576-2
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11340-019-00576-2