Statistical Investigation of the Influence of Maximum Shear Stresses Induced by Thermal Treatments on Fracture Toughness of Soda-Lime Silica Glasses: Comparison between Hertzian and Vickers Indentations

摘要

Hertzian and Vickers indentation tests have been performed to estimate the hardness and the fracture toughness of a soda-lime silica glass fabricated by the float process. A comparison between as-prepared glass, annealed glass (90 min at 680°C), and tempered glass (quenched from 660°C to 25°C) has been conducted to investigate the influence of thermal treatments on fracture toughness. In this study, a new method based on acoustic emission, recorded during Hertzian indentation tests, has been used in order to determine precisely the minimum load for fracture of these glasses having various thermal histories. Experimental results have shown the existence of a threshold load below which no crack can be propagated in glass. These critical loads have been used to determine Weibull's fracture laws as a function of surface quality and maximum shear stresses. It has been also shown that the presence of residual stresses induced by quenching leads to a shift of this threshold load and modifies Weibull's laws. Therefore, this method, which requires no measurement of any crack length, can be used to accurately estimate residual stresses induced by quenching in soda-lime silicate glasses.