A comparison of 2D and 3D digital image correlation for a membrane under inflation

Abstract

Three-dimensional (3D) digital image correlation (DIC) is becoming widely used to characterize the behavior of structures undergoing 3D deformations. However, the use of 3D-DIC can be challenging under certain conditions, such as high magnification, and therefore small depth of field, or a highly controlled environment with limited access for two-angled cameras. The purpose of this study is to compare 2D-DIC and 3D-DIC for the same inflation experiment and evaluate whether 2D-DIC can be used when conditions discourage the use of a stereo-vision system. A latex membrane was inflated vertically to 5.41 kPa (reference pressure), then to 7.87 kPa (deformed pressure). A two-camera stereo-vision system acquired top-down images of the membrane, while a single camera system simultaneously recorded images of the membrane in profile. 2D-DIC and 3D-DIC were used to calculate horizontal (in the membrane plane) and vertical (out of the membrane plane) displacements, and meridional strain. Under static conditions, the baseline uncertainty in horizontal displacement and strain were smaller for 3D-DIC than 2D-DIC. However, the opposite was observed for the vertical displacement, for which 2D-DIC had a smaller baseline uncertainty. The baseline absolute error in vertical displacement and strain were similar for both DIC methods, but it was larger for 2D-DIC than 3D-DIC for the horizontal displacement. Under inflation, the variability in the measurements were larger than under static conditions for both DIC methods. 2D-DIC showed a smaller variability in displacements than 3D-DIC, especially for the vertical displacement, but a similar strain uncertainty. The absolute difference in the average displacements and strain between 3D-DIC and 2D-DIC were in the range of the 3D-DIC variability. Those findings suggest that 2D-DIC might be used as an alternative to 3D-DIC to study the inflation response of materials under certain conditions.

Geometry of an inflated membrane in elliptic bulge tests: Evaluation of an ellipsoidal shape approximation by stereoscopic digital image correlation measurements

“…In that regard, field measurements appear as a valuable and practical solution when a detailed knowledge of the all sample mechanical state is needed. However, when such methods as stereoscopic DIC cannot be used, the alternative methods and hypotheses taken to infer information from scarcer measurements need be to carefully investigated to get a clear idea on how they impact the obtained results [19].…”

Material characterization of curved shells under finite deformation using the virtual fields method

“…As shown in Table A2, a value of 1 μm is representative for the out-of-plane displacement noise levels found in the experiments. [17,18] The noise…”

“…Behind the membrane is an air-filled cavity, which is connected to a pressure generator and a pressure gauge amplitude was the same for all displacement components, even though in-plane displacements obtained with DIC would have lower noise amplitude. [17,18] Therefore, the simulations intent to consider extreme conditions that are worse than the experimental ones in order to provide an upper bound of the effects of noise. As an example, in Figure 5a-f, we show simulated displacements and strains at a pressure level of 1 kPa.…”

Deformation Monitoring System Based on 2D-DIC for Cultural Relics Protection in Museum Environment with Low and Varying Illumination

“…Digital image correlation (DIC) among other optical nondestructive testing (NDT) methods is becoming more widely accepted for materials and structural monitoring. The two-dimensional DIC is applied to a series of images of a deforming planar object acquired by a single camera [8]. The surface of the object is speckled to present a randomly distributed intensity pattern.…”