Effect of Post-processing Parametres on the 2D Digital Image Correlation Results

Digital image correlation technic (DIC) present a full field strain measurement method employed during experimental test execution. Displacement or strain measurements are carried out through the correlation between the reference image and the images captured along the test. Several studies were investigated based on the DIC method, but the effect of the post-processing parameters on the reliability of the results has not been fully investigated. In this context, the 2D DIC technic is employed during the 4-point bending tests on different composite tube types. Single tube and butt-welded joined tubes according to the NFT57-900 and the DIN16966 standard are tested. Then, a parametric study was conducted, based on the variation of the grid step and the pattern analysis size. The results obtained by the different parameter value combinations are validated by comparison with the machine stress-strain obtained curve. The various parameters couple combinations prove that the more the grid step and the analysis pattern size are increased, the more the deformation decreases and converges to the results obtained by the machine. Furthermore, the accuracy of the 2D DIC technic measurement is influenced by the speckle quality. Finally, the 2D DIC method predicts well the quasi-elastic behavior of the composite material.