JIANG Xinzhao, LIU Shujiang, SHEN Jianxing

(Key Laboratory of Processing and Testing Technology of Glass & Functional Ceramics of Shandong Province,
Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, Shandong, China)

Abstract: The viscous relaxation time of glass at room temperature is too long that to detect the viscous flow. However, permanent deformation can be easily realized under sharp diamond indenter. Crack initiation and permanent deformation of soda lime silica glass were studied by using a Vickers indentation tester. The deformation of glass is divided into two deformation processes: plastic (or shear) flow and densification. Plastic flow is the volume conservative displacement of material, while densification is the irreversible compression of non-volume conservation. In this work, the mechanical properties of soda lime silica glass were tested by using indentation method, where the influence of the network connectivity and applied load on deformation and fracture behavior of the glass was emphasized. It is found that, when the network connectivity is sufficiently low (i.e. high content of non-bridging oxygen), the glass has high atomic packing density and low molar volume, resulting in high elastic modulus and Poisson's ratio, high hardness and brittleness, low toughness and weak cracking resistance. On the contrary, when the network connectivity is high, densification is the characteristic of the whole indentation process. The higher the degree of densification in the glass, the stronger the crack resistance the glass will have, which is reflected by the great reduction in the residual stress of the indentation after annealing treatment.
Key words: network connectivity; densification; crack resistance