VICKERS INDENTATIONS IN GLASS .1. RESIDUAL-STRESS FIELDS AND ISO-STRESS CONTOUR MAPS

This paper describes an experimental approach to measure the residual stress field around Vickers indentations in soda-lime glass. The metho d uses a small indentation as a microprobe to measure the residual str ess at a specific position near a large indentation. Extensive experim ents have been performed and the residual stresses field around a 45 N Vickers indentation were mapped. The relation between the residual st ress and the distance from the indentation was determined along severa l specific directions from the indentation based on numerical regressi on. The residual stress field around the Vickers indentation is a non- equal bi-axial stress field. Both residual tensile stress and compress ive stress show a power law relation with distance from the indentatio n. These relations are angle dependent. The iso-stress contours of bot h residual tensile and compressive stresses are then determined from t he experiments. A self-calibration experiment, i.e. indentation on pre -stressed glass bending bars, was specially designed to confirm the ac curacy of the experiments and the analysis. The present experiments an d the analysis are accurate as long as the residual stress is larger t han 10 MPa.