Measurement of macro-scale indentation modulus using the primary hardness standard machines at INRiM

In this paper it is described the experimental procedure and the statistical method for the measurement of indentation modulus by using the primary hardness standard machine at INRIM, in the macro-scale range. Indentation modulus is calculated on the basis of Doerner-Nix linear model and from accurate measurements of indentation load, displacement, contact stiffness and Vickers hardness impression imaging. Load is provided by dead-weight masses and displacement is measured by a laser-interferometric system, perpendicular with respect to the Vickers pyramid vertex. The geometrical dimension of the Diamond Pyramid Hardness (DPH) impression is measured by means of a micro-mechanical system and optical microscopy imaging technique. Applied force and indentation depth are measured simultaneously, 16 Hz of sampling rate, and the resulting indentation curve is obtained. Preliminary tests are performed on metals and alloys samples. Considerations and comments on the accuracy of the proposed method and analysis are discussed.