FURTHER ANALYSIS OF THE SIZE EFFECT IN INDENTATION HARDNESS TESTS OF SOME METALS

The variation of apparent hardness observed in previously reported Vickers indentation tests of metals is reexamined, Common descriptions of the effect are shown to be inaccurate: the variation of apparent hardness is monotonic bur not simple, The effect is consistent with varying size of a previously postulated ''plastic hinge'' at the perimeter the indent. This complexity confers uncertainty on the estimation of characteristic macrohardness from small scale tests. Association of the indentation size effect with friction and with strain hardening is confirmed.