Fracture mechanics analysis of thermally tempered glass plate: fracture induced by an embedded crack

This paper presents a fracture mechanics analysis of a thermally tempered glass plate. The fracture is induced by an embedded penny-shaped crack. The analysis shows that the existence of a penny-shaped crack will reduce the strength of tempered glass. The impact and fatigue resistance of the glass is related to the position and size of the penny-shaped crack. When the tempering intensity reached to a certain level, thermally tempered glass with a penny-shaped crack could experience spontaneous fracture. The damage of a central crack on glass is more severe than a surface crack. With surface compression, thermal tempering will increase the critical applied stress of the glass if the surface penny-shaped crack size is in the range of 0 < a/d < 0.27, where a is the crack size, d is the half thickness of the glass plate. For a small surface crack with the size of a/d ≤ 0.09, the tempering can hinder its extension. However, if there is a central penny-shaped crack, the critical applied stress of the tempered glass will decrease with the intensity of tempering.