On Experimental Determination of Poisson’s Ratio for Rock-like Materials using Digital Image Correlation

Abstract

This article compares the two most used strain determination experimental techniques, the strain gauges and the digital image correlation (DIC), which are used here to determine the static Poisson's ratio of rock-like materials under a compressive loading. While the strain gauge technique measures the strains on the small patch of the underlying material on the spot, where the strain gauge is applied, DIC is a novel optical full-field technique that can measure the strains over the entire region of interest of the specimen. The key research question presented in this paper and research significance is to what extent the measurement of Poisson’s ratio is improved by leveraging the richness of the full-field measurements compared to the conventional strain gauge technique. To this purpose, the hypothesis was tested through virtual experiments in which a numerical simulation of a uniaxial compression test with a cylindrical, rock-like sample was created to mimic the strain gauge and DIC measurement techniques, as well as by conducting an actual compression test on a sandstone material. In contrast to conventional strain gauges, novel optical techniques such as stereo DIC proved to be able to capture the macroscopic Poisson coefficient with higher precision, thus reducing the margin of error.