Berkovich nanoindentation of borosilicate K9 glass

Instrumented indentation was used to investigate the proportional relationships among indentation variables such as the maximum indentation displacement, contact depth, the ratio of load over contact stiffness, and the ratio of permanent displacement over the maximum displacement. Material and indenter were borosilicate K9 glass and a Berkovich indenter, respectively. Results of fused silica under the same indenter were compared. Load–displacement curves of K9 glass were characterized by power-law functions for both loading (power exponent of 2) and unloading (power exponent of 1.36) with hardness, elastic modulus, yield stress, and power strain hardening exponent being 7.72, 82.8, 3.5 GPa, and 0.6, respectively. Experimental results were found to be in agreement with theoretical prediction and dimensional analysis. The results calculated from energy-based method were found to be consistent with those based on Oliver and Pharr’s method. General implications of the scaling relations for indentation variables were discussed (e.g., the scaling expressions can be used to check indentation data).