Analysis of symmetric fracture mirrors in glass bottles

Fracture conditions which defined the mirror fracture that developed from random flaws were characterized in glass bottles. A constant ratio of the mirror constant to the critical stress intensity factor (A/K_IC) equal to 2.35 with a scatter of 12% was found. The sharp transition between the flaw and the mirror plane signifies an abrupt transition to rapid fracture propagation. The model implied by Shand that the mirror boundary is the loci of all points occurring at different times when conditions for bifurcation are reached, is confirmed. For this purpose both changes of stress with the thickness of glass wall and edge effects on the stress intensity factor were considered.