Dresden 2003 – wissenschaftliches Programm

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DS: Dünne Schichten

DS 21: Mechanische Eigenschaften

DS 21.3: Vortrag

Donnerstag, 27. März 2003, 11:30–11:45, GER/38

Integral and differential hardness - new concepts to quantify load-depth-data in nanoindentation experiments — •Bodo Wolf and Asta Richter — Technische Fachhochschule Wildau, Physikalische Technik, 15745 Wildau

Conventional hardness H proves a weighted mean of the deformation resistance from the very beginning of indentation up to the actual depth. Instead of calculating F/A the differential quotient Hd= dF/dA can be considered. This entity is a measure of the actual deformation resistance. Raising the load from F to F + dF results in a shell-like increase of the plastic zone, and Hd stands representative for the mechanical properties of this shell. In this paper the relationship between H and Hd will be mathematically deduced, and some experimental examples will be considered for illustration. Hardness may also be interpreted as density of plastic deformation work. Dividing the plastic work (the area encircled by loading and unloading curve) by the volume of the irreversibly displaced material delivers the integral or energetic hardness He. He and Hd equal H only, if the hardness is constant. When comparing to the conventional hardness it turns out that the differential hardness is more sensitive to the deeper layers whereas the energetic hardness proves more surface sensitive.