Hardness obtained from conical indentations with various cone angles

The relationship between hardness and cone angle of conical indenters was studied using finite element analysis for elastic-plastic solids with work-hardening. Comparisons were made between the present simulation results, slip line theory, and experimental results. Tabor's concept of representative strain based on indentation experiments in metals (The Hardness of Metals, Oxford, 1951) was shown to be applicable to a wide range of materials. The relative size of plastic zone with respect to the contact radius was found to influence the variation of hardness with indenter cone angle. The method proposed by Atkins and Tabor [J. Mech. Phys. Solids, 13, 149 (1965)] for constructing stress-strain curves using representative strains was also examined, and the conditions under which the method is valid were obtained.