Specific Features of Glass Damage and Fracture Resistance under the Rockwell Indenter Scratching of the Specimen Surface until the Edge Chipping Appearance

The paper presents the experimental results of investigations using different types of glass by the Rockwell indenter scratching of the specimen surface till its edge chipping (S+EF method). The peculiar features of the materials’ fracture are determined as a result of fractography analysis of the empirical data. It is proposed to classify chips under two different groups. The first group is characterized by the edge fracture that is accompanied by the fully developed shell-like chip with typical zones of the fracture crack propagation (traces of axisymmetric quasi-cone crack propagation). The second group of chips involves the edge fracture without smoothly outlined borders of the fracture crack propagation on the lateral surface of the specimen with a set of branched and randomly oriented cracks having the reflecting zone of comparatively small dimensions. The mechanisms of variation in the shape of chip scars (fracture crack propagation trajectory) are implied with the increase of the fracture load on the indenter or fracture distance. It is established that the fracture resistance is invariant to the fracture load and does not depend on the asymmetry of chip scars according to their side views. The authors demonstrate the correlation dependence between the test results (the S+EF and SEVNB methods) on the different glass types, which reveals the effect on the specified cracking and chipping of the material in the zone of its contact with indenter for fracture resistance of glass under local edge loading. The authors propose to use the methods of indenter scratching of the specimen surface till its edge chipping as the rapid assessment of damage and fracture resistance of glass in the solution to the optimization tasks, certification procedure or materials’ selection.