Nanoindentation of Soda Lime-Silica Glass: Effect of Loading Rate

Structural and mechanical reliability of glass for both conventional and advanced applications is determined by the rate at which it can deform and sustain externally applied static or dynamic strain at the microstructural length scale. Hence, a large number of nanoindentation experiments were conducted on a thin (similar to 300 mm) commercial soda lime-silica glass with a 150 nm radius Berkovich tip at a constant load of 10,000 mu N as a function of variations in the loading rates in the range of 10-20,000 mu N/s. The results showed that the nanohardness of the soda lime-silica glass increased by as much as 74% as the loading rate was increased from 10 to 20,000 mu N/s. Further, the presence of serrations in load-depth plots and deformation band formations inside the nanoindentaion cavities were more vividly observed in the nanoindentation experiments conducted at lower loading rates rather than those conducted at higher loading rates. These results are explained in terms of shear stress acting underneath the indenter as well as the time scale of interaction between the nanoindenter and the weak links at local microstructural length scale, which owe their origin to the subtle variations in the composition of the given glass.