Author(s)

Gerd Kaupp

University of Oldenburg, Oldenburg, Germany.

The Nanoindentation is a precise technique for the elucidation of mechanical properties. But such elucidation requires physically based interpretation of the loading curves that is widely still not practiced. The use of indentation hardness H and indentation modulus E_r is unphysical and cannot detect the most important phase-transitions under load that very often occur. The claim that H versus E plots relate linearly for all different materials is neither empirically found nor correctly deduced. It is most dangerous by producing incorrect materials properties and misleading. The use of H/E (that is also called “elasticity index”) in complicated formulas for brittle parameter, yield strength, toughness, and so-called “true hardness” is also in error. The use of H/E cannot reveal the true qualities of materials without considering phase-transitions under load that require the correct exponent 3/2 on h for the loading curves (instead of disproved 2). This is exemplified with the physical data of different mollusk shells that experience phase-transitions, a new bionics model, and different contributions for their strengthening. The data are compared to the ones of aragonite and calcite and vaterite.

Nanoindentation, H/E Ratio Challenge, Phase-Transitions, Penetration Resistance, Mollusk Shells, Aragonite, Calcite, Bionics

Kaupp, G. (2021) Undue Hardness/Modulus Ratio Claims instead of Physical Penetration Resistance and Applications with Mollusk Shells. Advances in Materials Physics and Chemistry, 11, 45-57. doi: 10.4236/ampc.2021.112005.