Spontaneous fracture of tempered glass is usually caused by expansion of phase transformation of NiS inclusion. I am curious about the size of fracture mirror of this kind of fracture. In practice, it is difficult to locate the fracture mirror around the NiS inclusion. I don’t know whether the fracture mirror is basically missing from this kind of fracture or it is just difficult to observe.
Spontaneous fracture of tempered glass due to nickel sulfide (NiS) inclusions is indeed a common issue. The phenomenon occurs as NiS undergoes a phase change from a high-temperature form (alpha-NiS) to a low-temperature form (beta-NiS), which causes an increase in volume and potentially induces enough stress to fracture the glass.
Now, regarding the fracture mirror: when a brittle material like glass fractures, it often produces certain characteristic features. These can include the mirror, mist, and hackle regions, which relate to the speed and direction of crack propagation. The mirror region, closest to the origin of the crack, is typically smooth and shiny, hence its name.
For NiS-induced fractures in tempered glass, a fracture mirror should theoretically be present around the NiS inclusion, which acts as the origin of the crack. However, it can indeed be very difficult to locate for several reasons:
Therefore, while a fracture mirror should be present in theory, it can often be very difficult to observe in practice. Methods like scanning electron microscopy (SEM) or other forms of microscopic analysis could potentially be used to locate and examine the fracture mirror if required.
Joshua Depiver Thanks for your reply. Do you know any books or papers that are regarding the fracture mirror of tempered glass? I only know about the paper from Dr. Kasper which clearly shows a fracture mirror caused by an inclusion: .
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