The Effect of Tempering and Wall Thickness on the Fracture of Pint Glasses

This study presents a comprehensive analysis of the effect of tempering and wall thickness on the fracture of tempered drinking glasses typically used in bars and pubs in the United Kingdom. The fracture patterns are related to the manufacturing process, the glass geometry, and the level of residual stress. The bulk of experimentation was split into two categories: Firstly, an assessment of the residual stress was conducted, followed by an assessment of the fracture response of the glass in practical applications. Drinking glasses have a variable wall thickness as a consequence of their design and manufacture. This has a direct effect on the level of residual stress in the article, which in turn produces glasses that break to give fragments of variable sizes, with large sharp-edged fragments nearer the glass rim. It is also shown that tempered glasses broken by impact have a characteristic fracture pattern. The results show that to control the fracture of glasses to produce small fragments similar to those in tempered flat glass, the wall thickness and resulting level of residual stress need to be optimized.