Phenomenology of the size effect in hardness tests with a blunt pyramidal indenter

Further detailed analysis of the indentation size effect exhibited by some single-phase metals leads to a new, very accurate, descriptive equation. Th is affords consistent and realistically low evaluation of macrohardness fro m micro-indentation test data. The indentation size effect exhibited by fused silica is also matched preci sely by the new description, demonstrating a common phenomenology regardles s of the different micromechanisms sustaining indentation. Comparison of data from standard and low-load Vicker's tests with data from ultra-microindentation with a Berkovich indenter establishes continuity of a monotonic size effect throughout the entire range of indent size. The observed size effects are consistent with the projected refinement of a previously proposed model of indentation that attributed the effect to var ying importance of the constrained flexing at the perimeter of the indent. The magnitude of the size effect appears to be a measure of the resistance to strain concentration in the perimeter flexure zone. The large size effec t for eminently plastic metals indicates that restricted micro-deformation capability is not the major cause, (C) 1998 Kluwer Academic Publishers.