Strain Measurement by Digital Image Correlation: Influence of Two Types of Speckle Patterns Made from Rigid or Deformable Marks

Abstract

For both 2D and 3D measurements by correlation techniques, speckle patterns can be composed of rigid particles (RP). In this paper, a study of the influence of these RP on digital image correlation (DIC) strain error assessment is performed experimentally and numerically. Firstly, it is shown that prior to the influence of pattern, it is necessary to have an appropriate calculation strategy of initial values for DIC iterative process. Then for simulated images, the RP pattern presents a similar behaviour as the one of a deformable pattern to which a noise is added. However, for experimental images, this noise is less predominant on error assessment than the one because of deteriorations of patterns for large strains.

Application of optical methods to investigate the non-linear asymmetric behavior of ceramics exhibiting large strain to rupture by four-points bending test

“…It has a low thermal expansion coefficient (0.1-1.10 −6 K −1 ) and low Young's modulus (8)(9)(10). Besides, it can be used in several applications due to its good thermal shock resistance at temperature lower than 1000 • C due to its instability at high temperatures.…”

“…In this study the experimental measurements were obtained thanks to DIC for fields strain measurements and mark tracking method for local study. [4][5][6][7][8][9][10][11][12] DIC is based on the analysis of successive digital images of a same sample during a mechanical test. The displacement fields are obtained by measuring the degree of similarity of series of subsets between the image corresponding to an unloaded state and the deformed image recorded during the test.…”

“…The material transformation is then composed of 2 rigid displacement parameters (u,v) and 4 local gradients parameters ∂u ∂x , ∂u ∂y , ∂v ∂x , ∂v ∂y . The degree of similarity between f and g, which correspond respectively to the gray levels of the reference and the deformed states, is given by the minimization of the correlation coefficient C 6,9,11 :…”

“…This non-contact optical method directly provides full-field displacements by comparing the digital images of the sample's surface obtained before and during deformation. [4][5][6][7][8][9][10][11][12][13] Recent works on AT using DIC, 14,15 have been performed so as to identify its behavior related to the damage law and the cracking behavior. In the present work, the asymmetry between compression and tension of AT has been studied to highlight the complex behavior of this material.…”

Rendering Deformed Speckle Images with a Boolean Model

“…DIC assessment is, however, likely to be affected by the interpolation scheme. In order to reduce the influence of interpolation, a possibility is to generate low-resolution images by binning pixels of an interpolated high-resolution deformed speckle image [4,6,7,10,18,31,41].…”