An Advance Study on Physical Nanoindentation: From Penetration Resistance to Phase-transition Energies

Abstract

The ISO standard 14577 is contested due to its iterative processes, violation of the energy law, and incorrect relationships between the normal force (F_N) and impression depth (h). The solution of this dilemma is the use of sacrosanct simplest calculation rules for the loading parabola (now F_N = kh^3/2) giving straight lines for cones, pyramids and wedges. They provide the physical penetration resistance hardness k with dimension [Nm^-3/2] upon plotting and allow for non-iterative calculations with closed formulas, using simple undeniable calculation rules. The physically correct F_N versus h^3/2 plot is universally valid. It distinguishes between the most typical surface effects and makes gradients visible. Unmatched precision is provided, including reliability analyses of experimental data. A regression study of the F_N vs h^3/2 graphs demonstrates that the transition-energy coincides with the beginning of the kink-unsteadiness phase transition. All types of solid materials, including salts, silicon, organics, polymers, composites, and superalloys, are shown to exhibit this. The abrupt phase-transition onsets and transition energies offer unheard-of most crucial material properties that are essential for safety. As a result, ISO ASTM is requested to modify ISO 14577 in its entirety and to develop new standards for mechanically (and thermally) stressed materials. For instance, materials must only be admitted for maximal forces considerably below the first phase-transition commencement, and the consistency of the first phase-transition parameters must be controlled. These onset loads can now be calculated with ease. Even nevertheless, persistent arguments against the physical analysis of indentations are based on severely inadequate understanding of fundamental mathematics and mistakes. The properties of the current nonphysical materials are reviewed with regard to their effects on safety.