Assessment of surface-local strains from remnant microindents on a Zr-based metallic glass

Abstract

In this study, a morphological modeling was done for remnant microindents on a Zr-based metallic glass for avoiding an overestimation in the indented surface area by applying the Riemann integral and for calculating quantitative values of the stretch strain which is defined by the indented surface area divided by its projected area according to Milman et al. A discrete pixel image for an indent was fitted into a continuous ellipsoidal cap and its indented surface area by a spherical indenter was deterministically calculated by integrating the ellipsoidal cap surface. The calculated stretch strains were lower than their upper limits and quantitatively close to the conventional indentation strains. The stretch strains were generally higher than the conventional indentation strains but decreased to their lower values at a shallow indentation of less than 50 μm. This phenomenon was attributed to severe elastic recovery in shallow indentations. From an overall viewpoint, the strain overestimation by the Riemann integral was clearly resolved, and this result confirmed the validity of the new approach for estimating the indented surface area and the stretch strain.