Journal of Materials Science, Vol.33, No.11, 2937-2947, 1998
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. This affords consistent and realistically low evaluation of macrohardness from micro-indentation test data. The indentation size effect exhibited by fused silica is also matched precisely by the new description, demonstrating a common phenomenology regardless 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 varying 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 effect for eminently plastic metals indicates that restricted micro-deformation capability is not the major cause,