Nanobiotechnology

Biography

Biography: Gerd Kaupp

Abstract

One of the most used and versatile techniques for (nano)mechanics is the indentation with pyramidal/conical diamond tips. ISO-14577 defines and iterates hardness (H_ISO) and elastic modulus (E_rISO) with respect to projected contact area (A_hc= const∙h_c²) with (nearly) legal character. This has been widely accepted since half a century, as it seems to support the Sneddon normal force (F_N) proportionality with h² hypothesis, which however has been disproved experimentally. And the proportionality with h^3/2 is physically founded. The wrong exponent 2 on h has not only been used for the unphysical deduction of most mechanical parameters but, unlike F_N=kh^3/2 plots since 1990 (where k is the material's penetration resistance), it cannot detect frequent phase-transformation in the loading curve, so that numerous unloading curve iterations from F_Nmax do not characterize pristine material. Even worse, these ISO standards violate the first energy law, because the concomitant shear-force work and thus not all of F_Nmax "arrives" at the projected area (published since 2012). The physically valid H_PHYS can now be obtained by linear regression of the loading curve's F_N=kh^3/2 plots (E_rPHYS requires additionally stiffness) and depth correction, omitting iterations with simplest arithmetic. It is thus valid for all types of materials and all instrumental indentation techniques. The dilemma of the ISO standards against physics and thus the enforced calculation of wrong mechanical properties is detrimental, producing very large errors (exponential size dependence!) and liability problems in case of materials failure. Textbooks and instrument software must be rewritten, ISO-14577, a NIST tutorial and numerous publications must be retracted. The physical correctness must be installed for the sake of daily life security. Examples will be discussed. ISO appears slow in changing its standards for complying with physics. They are asked to release an urgent caveat, telling that ISO-14577 will be subject to redefinitions for physical reasons.