Dynamic Indentation Hardness of Metals

Abstract

An experimental technique for determining the dynamic indentation hardness of materi- als is described. Unlike the traditional static hardness measurements, the dynamic hard- ness measurements can capture the inherent rate dependent material response that is germane to high strain rate deformation processes such as high speed machining and impact. The dynamic hardness of several commonly used engineering materials is found to be greater than the static hardness. The percentage increase in hardness is found to be strongly dependent on the crystal structure of the materials used in this study. Micro- structural analysis of static and dynamic indentations on metals with FCC, BCC, and HCP crystal structures revealed that the indentation volume size is a function of plastic properties under static and dynamic conditions. Finite element simulations of the dynamic indentation event indicated that an increase in yield stress and work hardening rate decrease the size of the developed plastic zone beneath the indenter.