Abstract:

Tempered glass is widely used in building and furniture as a type of safety glass. However, spontaneous breakage of tempered glass is a serious problem known as "glass cancer" characterized by sudden and catastrophic. It is important to reduce, prevent and predict this phenomenon of spontaneous breakage of tempered glass through preparation and application. This study focused on the mechanism of spontaneous breakage of tempered glass and provided the answers on the reasons of spontaneous breakage. The critical conditions including internal and external influence factors on spontaneous breakage were discussed. It is demonstrated that the spontaneous breakage of tempered glass is caused by stress concentration in glass itself while the stress concentration may result from various particles or defects in the glass. Furthermore, local strength is defined for tempered glass which is non-linear distributed along thickness of the glass together with residual stress. The maximum of the local strength occurs at surface of tempered glass, while the lowest value is at neutral layer. The fundamental reason behind spontaneous breakage of tempered glass is that the stress concentration in the glass exceeds local strength, while impurities, such as nickel sulfide or monolithic silicon particles traditionally considered as the breakage causes, are actually indirect causes. A criterion for spontaneous breakage of tempered glass is also revealed which is useful for analysis of breakage of glass.

Key words: tempered glass, spontaneous breakage, local strength, residual stress