The size effect in microindentation

Abstract

The theory by Stelmashenko et al., De Guzman et al. and Nix and Gao of the size effect in microindentation is outlined and some implicit assumptions are discussed. By an algebraic rearrangement, the slope of the straight-line plot of the square of hardness against the reciprocal of the diameter or depth of an indentation acquires a value which is predictable and in order of magnitude in agreement with experiment. The corresponding scale length, of order 1 micron in copper, is thus a real physical property of the material, although it is not visible in the undeformed material. In the recent experiments of Motz et al. it is observed directly. The two-phase ‘hard metal’ WC-Co has a microscopic intrinsic scale length, accordingly, the plot is no longer linear.

Acknowledgments

Section 3 was stimulated by a discussion with A.S. Argon; D. Kuhlmann-Wilsdorf drew our attention to the work of L.D. Dyer.