Multiscale approach of hardness in aluminium alloy: Consideration of rate dependent behaviour

Abstract

Many materials display strong indentation size effects regarding hardness when the material and characteristic length scales associated with non-uniform plastic deformation are of the same order at micrometre and submicrometre levels. The failure of classical mechanics to predict these size effects has led to a multiscale mathematical approach that could significantly impact the issue of bridging the nano-, micro- and mesoscales. In the present work, a multiscale approach of hardness in engineering aluminium alloys is performed by mathematical modelling based on gradient methods and verification by nanoindentation and microindentation experiments. Furthermore, in order to bridge the different scales and to consider comprehensively these issues, rate dependent measurements are considered. The highly localised plastic deformation appearance under the nanoindentation is also investigated through pile-up deformation consideration.

Plastic Deformation of Rough Metallic Surfaces

“…This gives P ≈ 0.8 GPa which is in good agreement with other studies, e.g., P ≈ 1.033 and 0.806 GPa as found for two different aluminum alloys in Ref. [41]. However, note that the top surface area of the flattened macroasperities occupy only ≈ 40% of the nominal contact area in In fact, if a plastically deformed macroasperity contact area is observed at higher magnification, then short wavelength roughness can be observed, and an even smaller fraction than ≈ 40% of the nominally contact area may be plastically deformed (see also Sect.…”

Evidence that metallic proxies are unsuitable for assessing the mechanics of microwear formation and a new theory of the meaning of microwear

“…Several scale-related phenomena may be important. The hardness of some metals is much greater at the nanoscale due to an ‘indentation size effect' [ 20 ]. Also, the hardness of the spheres may not be uniform throughout their thickness.…”

Hardness across the multi-scales of structure and loading rate: A post-meeting response to the ‘pre-editorial’

“…17 It was notable that indentation rate (and deformation rate) effects, a theme touched on only obliquely in the pre-editorial questions above, attracted significant interest in the symposium that is reflected in the contributions to this issue. [18][19][20][21][22]…”