Speckle Pattern Improvements for Digital Image Correlation to Capture Small Strains in Tensile Tests on Rock

Digital image correlation (DIC) is a popular optical strain measurement technology for deformation analysis in rock mechanics laboratory testing. Although reliable and repeatable, traditional gauge extensometer techniques have drawbacks including high recurring cost limited spatial distribution of data. DIC utilizes continuous photography computer software to track paint speckle pixel displacements material deforming under load, producing full-field map each recorded increment. presents an opportunity overcome the limitations methods, significant precision care required typical total 0.005 mm (0.01% strain) Brazilian tensile stress (BTS) tests igneous sedimentary specimens measuring 47.6 diameter. For algorithms precisely individual pixels between frames, it often necessary apply unique pattern conforming several criteria specimen. A variety application been reported literature; however, importance high-quality resulting influence on accuracy results frequently overlooked. The testing program this research utilized 2-Dimensional BTS investigate cost, efficiency, ease application, effectiveness methods. In addition spraypaint, airbrush, stamp innovative laser engravement technique was developed that provides more results. This practical recommendations small 2D measurements.