Comparing 2D and 3D digital image correlation for an inflation test

Abstract

3D digital image correlation (DIC) is widely used in biomechanics to measure the deformation of 3D structures. However, 3D-DIC implementation can be challenging under specific conditions, such as high magnification (i.e. low depth of focus) or environment with limited access for two-angled cameras. Here, we aimed to compare 2D-DIC and 3D-DIC for the same inflation test, to evaluate 2D-DIC as an alternative to 3D-DIC under those conditions. A two-camera stereovision system acquired top-down images of a membrane inflated vertically to 5.41 kPa (reference pressure), then to 7.87 kPa (deformed pressure), while a single camera system simultaneously recorded side images. 2D-DIC and 3D-DIC were used to calculate vertical (out of membrane plane) and horizontal (in membrane plane) displacements, and meridional strain. Under inflation, the variability in displacements and strains was larger than under static conditions for both DIC methods. 2D-DIC showed a smaller variability than 3D-DIC, especially in the vertical displacements, and the absolute difference between the averaged 3D-DIC and 2D-DIC data was in the range of the 3D-DIC variability. The meridional strain uncertainty was similar between both DIC methods. Those findings suggests that 2D-DIC might be an alternative to 3D-DIC for inflation under certain conditions.