Densification modeling of fused silica under nanoindentation

Fused silica is the reference material used for estimating the area function of nanoindenter tips. Despite being a fundamental step in nanoindentation, little has been done to study its deformation. Under a complex state of stress during indentation, fused silica densifies pointing out that the hydrostatic stress contributes to its yielding. A linear Drucker-Prager model is successfully employed to describe fused silica deformation. Real tip geometry obtained from Atomic Force Microscopy (AFM) is utilized to numerically simulate the area calibration process. Our results indicate a significant discrepancy between the tip area input into our simulation and the one obtained by the calibration process. This implies that the estimated area is not an intensive property of the indenter tip but a convolution of the indenter geometry by the fused silica deformation characteristics and as such may produce erroneous values when used on other materials.