Estimating macro-, micro-, and nano-hardness of metallic materials from elasto-plastic finite element results
Journal Title: Frattura ed Integrità Strutturale - Year 2012, Vol 6, Issue 19
Abstract
This paper summarises an attempt of estimating macro-, micro-, and nano-hardness of metallic materials through conventional elasto-plastic finite element (FE) analyses. In more detail, to verify if the classical FE method can successfully be used for such a purpose, initially a series of hardness testes were carried out on three metallic materials characterised by a different elasto-plastic behaviour, i.e., aluminum alloy 7075-T6, low-carbon steel BS970-En3B, and, finally, austenitic steel AISI 316L. Subsequently, by making the indentation force vary in the range 490 N-490 μN, Vickers hardness was estimated from elasto-plastic FE models done by using, to calibrate the mechanical properties of the investigated metals, the corresponding monotonic stress-strain curves experimentally determined by testing samples having both conventional size and, for austenitic steel AISI 316L, gauge length size equal to approximately 100 μm.The systematic comparison between experimental results and numerical simulations suggests that the increasing of the measured hardness value with the decreasing of the indenter size may directly be ascribed to the role played by the actual morphology of the material being tested. In particular, it is seen that conventional elasto-plastic continuum mechanics is no longer adequate to estimate metallic material hardness as the size of the indented surface approaches the average size of the grains. Finally, in order to overcome the above limitation by allowing the classical elasto-plastic FE approach to be used also to estimate nano-hardness, a simple engineering method is proposed and subsequently validated through the generated experimental results.
Authors and Affiliations
Luca Susmel, David taylor
Keywords
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- EP ID EP113885
- DOI 10.3221/IGF-ESIS.19.04
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