Edge chipping of borosilicate glass by blunt indentation

The edge chipping of borosilicate glass by smooth steel and ceramic spherical indenters was investigated experimentally. Indentation near an edge typically formed Hertzian cracks beneath the indentation plane which then grew to asymmetric cone cracks intersecting the side wall. Although these early stages of crack propagation always followed the same general pattern, the ultimate failure of the edge could involve splitting parallel to the side wall, flaking, fragmentation, or crushing the edge. The nature of the failure depended on the constraint of the indenter, the indenter material, and the indentation distance from the edge. These patterns of edge chipping are quite different from those observed with sharp indenters. The results have application in manufacturing processes aimed at producing rounded edges in brittle materials or in situations where edge chipping is to be avoided.