A Parametric Study on the Influence of Internal Speckle Patterning for Digital Volume Correlation in X-Ray Tomography Applications

Use of the Digital Volume Correlation (DVC) technique has grown steadily in the mechanics community as a way of quantifying internal mechanical response of complex microstructures under loading. The DVC technique has been combined with internal imaging methodologies such as X-ray microcomputed tomography (X-ray microCT), confocal microscopy, and photoelasticity enabling many full field studies of bone, foam, rock, polymers, and metals. Despite all these efforts, many DVC limitations remain unknown such as those of "optimal" subset size, step size, and the quality of an internal speckle pattern. Here we investigate in detail the effects of internal speckle patterning on DVC. To help determine the optimum setup for DVC, we develop internal speckle patterns using markers ranging from 5 to 50 mu m particles and study these over different resolution length scales. A correlation of pattern size and quality was determined using baseline (i.e., no deformation) and rigid body motion experiments, resulting in a recommended pattern quality parameter. We then performed a uniaxial compression experiment using the optimal pattern determined from the parametric study where we compare accuracy using DVC calculated strains and displacements with theoretical values. An in situ uniaxial compression test demonstrated DVC capabilities resulting in a 2 % error in strain computations.