Role of shear stress in scratch deformation of soda-lime-silica glass

Various advance applications of glass demand high precision grinding and polishing of glass, a typical brittle material. The grinding and polishing are basically material removal by multiple scratches. In spite of the wealth of literature on soda-lime-silica glass, unfortunately however, the magnitudes of the maximum shear stresses generated beneath the moving indenter and the patterns of the shear stress contours are yet to be comprehensively understood. The stress beneath the indenter is required to be known to understand in a better way the damage evaluation processes as well as the material removal mechanisms as shear stress is the most important component of the stress tensor. Therefore, to develop a better understanding about the damage evolution and consequent material removal mechanisms the shear stress contours beneath the scratches made at four different normal loads of 2, 5, 10 and 15 N at scratching speed of 500 μm/s were predicted using the Hertzian contact analysis. The extensive use of field emission scanning electron microscopy (FESEM) of the sub surface regions of the SLS glass revealed that three zones exist in the sub-surface region of the scratch grooves. The spatial extents of these three zones measured from the actual photomicrographs and the predictions were comparable.

► The shape of the stress contours beneath the indenter for SLS glass.
► The variation of shear stress in both radial and depth directions beneath the moving indenter in scratch experiments.
► The cause of existence of three zones in the sub-surface region of the scratch grooves.