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

Abstract

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 applying the Doerner-Nix linear model; indentation work, representing the mechanical work spent during the force application of the indentation procedure, was determined by calculating the areas under 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 interferometric system. Applied forces and the occurring indentation depths were simultaneously measured: the resulting loading–unloading indentation curve was achieved. Illustrative tests were performed on metals and alloy samples. Discussion and comments on the suitability of the proposed method and analysis were reported.

Combined First-Principles and Experimental Study on the Microstructure and Mechanical Characteristics of the Multicomponent Additive-Manufactured Ti–35Nb–7Zr–5Ta Alloy

“…It is evident that the load–depth curve is continuous, without any large steps (pop-ins or pop-outs). Based on ref , we calculated the corresponding elastic recovery ratio (19.35%) and the value of characteristic plasticity (80.65%), which are consistent with the collected data of the elastic part of indentation work (19.16%) and detected the domination of plastic deformation. Moreover, no cracks are observed in the typical nanoindentation imprint, indicating the plastic behavior of TNZT.…”

Effect of twist on indentation resistance

“…Further work could apply or develop Eqs. ( 8) to (18), or other 3D analysis methods [43][44][45][46][47], for off-centre contact with the unit cells, non-symmetric indenters, or anisotropic materials, where deformations in the third axis may be imbalanced. Such work could facilitate better understanding of the effect of twist during indentation, and inform the design of simpler to make, 2D extruded (orthotropic) twisting lattices.…”

Effects of Stress-Strain Data Synchronisation Errors on the Determination of Young’s Modulus of Hard and Soft Materials in Material Testing Machines

“…The resulting force is measured by means of a 100 kN load cell. Displacement is evaluated, from DIC technique, in several regions of the sample and the mean value is used [3]. The displacement rate is set to 0.1 mm/min.…”