Direct determination of the contact area based on the concept of rounded indenter tip correction for Berkovich nanoindentation tests: Case study on silica glass

Determination of the contact area is a key issue for extracting the mechanical properties from the analysis of nanoindentation load-displacement (P-h) curves. In this paper, a new method for the direct determination of the contact area with the empirical equation A = C (H_c + H_d )² was proposed. It is based on the consideration of round indenter tip correction, using the correction factor H_d yielded by fitting the loading segment of the measured P-h curve and the contact depth H_c determined from the unloading segment of the same curve. Thus, the mechanical properties can be extracted easily and directly without the need of the pre-calibration of area function. The applicability of this new method was examined by statistical analysis of a total of 497 nanoindentation tests performed on silica glass. It was shown that reliable results of Young’s modulus and hardness can be obtained based on the proposed new method.