Indentation Modulus, Indentation Work and Creep of Metals and Alloys at the Macro-Scale Level: Experimental Insights into the Use of a Primary Vickers Hardness Standard Machine

In this work, the experimental method and the calculation model for the determination of indentation moduli, indentation work, and indentation creep of metallic materials, by means of macroscale-level forces provided by a primary hardness standard machine at the National Institute of Metrological Research (INRIM) at the at room temperature were described. Indentation moduli were accurately determined from measurements of indentation load, displacement, contact stiffness and hardness indentation imaging and from the slope of the indentation unloading curve by apply-ing the Doerner-Nix linear model; indentation work, representing the mechanical work spent dur-ing the force application of the indentation procedure, was determined by calculating the areas un-der the loading–unloading indentation curve, through fitting experimental data with a polynomial law. Measurements were performed with a pyramidal indenter (Vickers test). The applied force was provided by a deadweight machine, and the related displacement was measured by a laser inter-ferometric system. Applied forces and the occurring indentation depths were simultaneously meas-ured: the resulting loading–unloading indentation curve was achieved. Illustrative tests were per-formed on metals and alloy samples. Discussion and comments on the suitability of the proposed method and analysis were reported.