Micro-Photoelastic Evaluation of Indentation-Induced Stress in Glass

Abstract

In this study, micro-photoelastic measurements were performed to obtain three-dimensional stress maps of silica and soda-lime glasses during ball indentation. The stress components were calculated from retardations and azimuths, which were determined from photoelastic measurements with a spatial resolution of about 1 µm. During loading, it was observed that the tensile stress in the radial direction is generated near the surfaces of both glasses. During unloading, however, it was found that stress distributions of silica and soda-lime glasses are different from each other. It is concluded that the different stress distributions during indentation result in different crack geometries, ring and radial cracks.

Fig. 4 Principal stress maps of (a) silica and (b) soda-lime glasses under a ball indenter. The origin of each stress map corresponds to the contact point between the indenter and the glass. The positive values (red) and negative values (blue) indicate tensile and compressive stresses, respectively. Fine black lines denote directions of principal stresses.