Abstract
A new experimental method for measuring strain fields in highly deformable materials has been developed. This technique is based on an in-house developed Digital Image Correlation (DIC) system capable of accurately capturing localized or non-uniform strain distributions. Thanks to the implemented algorithm based on a Semi-Global Matching (SGM) approach, it is possible to constraint the regularity of the displacement field in order to significantly improve the reliability of the evaluated strains, especially in highly deformable materials. Being originally introduced for Digital Surface Modelling from stereo pairs, SGM is conceived for performing a one-dimensional search of displacements between images, but here a novel implementation for 2D displacement solution space is introduced. SGM approach is compared with the previously in-house developed implementation based on a local Least Squares Matching (LSM) approach. A comparison with the open source code Ncorr and with some FEM results is also presented. The investigation using the present DIC method focuses on 2D full-field strain maps of plain and notched specimens under tensile loading made of two different highly deformable materials: hot mix asphalt and thermoplastic composites for 3D-printing applications. In the latter specimens, an elliptical hole is introduced to assess the potentiality of the method in experimentally capturing high strain gradients in mixed-mode fracture situations.
Highlights
Experimental solid mechanics testing often requires accurate measurements of full-field strain components
This paper summarizes the most significant experimental studies performed using Digital Image Correlation (DIC)-based techniques on the two different high deformable materials, comparing strains registered by different DIC stereo matching algorithms with finite element simulations
Deformation components are calculated according to the Green-Lagrange finite strain tensor, which, in the case of small displacement gradient compared to unity, coincides with the small strain tensor
Summary
Experimental solid mechanics testing often requires accurate measurements of full-field strain components. Kim and Wen [6] first proposed the use of DIC technique as a possible displacement/strain measurement method for asphalt mixture.
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