Transparent brittle ceramics such as soda-lime glass pose unique challenges for performing full-field optical measurement of deformations and stresses to characterise fracture and failure behaviours. Low fracture toughness, coupled with high stiffness and elastic wave speeds are among the factors responsible for some of these challenges as deformations tend to be small and confined to an extremely small region near the stress concentrators. Need for strong birefringence, elaborate optics, or lack of sufficient measurement sensitivity are some of the factors against legacy techniques such as photoelasticity, optical interferometry, and speckle methods, respectively, to study soda-lime glass. Motivated by these factors, the feasibility of Digital Gradient Sensing (DGS) method to measure crack-tip and contact-induced deformations in soda-lime glass under quasi-static loading is demonstrated. This first of a two part paper demonstrates the applicability of DGS for the problem under quasi-static loading conditions. The optical measurements are used to evaluate relevant parameters and compare with the analytical solutions. The second part of this study is focused on measuring contact-point and crack-tip deformations during impact-induced stress wave loading.
