THE INDENTATION LOAD SIZE EFFECT AND THE MEASUREMENT OF THE HARDNESS OF VITREOUS SILICA

The indentation load/size effect (ISE) for the Knoop microhardness measurement of vitreous silica is considered for indentation in different test environments. Analysis was through the application of Meyer's Law. the Hays/Kendall approach of a critical load for the initiation of flow and the proportional specimen resistance (PSR) model proposed by Li and Bradt. The PSR model in combination with a normalized form of Meyer's Law was found to describe consistently the measurements and to yield a load-independent Knoop microhardness for fused silica of 540 kg/mm2. The model also explains the effects of different indentation test environments, suggesting the effect is a result of their lubricating effects at the indenter facet/specimen interface.