Instrumented indentation of fused silica by Berkovich indenter

Scaling 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 were investigated via Berkovich indentation of fused silica. Load-displacement curves were characterized by power-law functions for both loading and unloading. The power exponents can be assumed to be constant for loading and unloading. Hardness, elastic modulus, and yield stress were measured to be 9.8 GPa, 73.3 GPa, and 5.5 GPa, respectively, for fused silica that can be assumed to be elastic-perfectly plastic. The empirical algorithm for estimating yield stress was verified for fused silica. The experimental results accorded well with theoretical prediction and dimensional analysis. The expressions obtained can be used to check indentation data, and general implications of the relations are discussed.