Berlin 2018 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 4: Topical session (Symposium EPS and MM): Mechanical Properties at Small Scales

MM 4.3: Vortrag

Montag, 12. März 2018, 11:00–11:15, TC 006

Plastic Poisson’s Ratio of Nanoporous Metals: A Macroscopic Signature of Tension-Compression Asymmetry at the Nanoscale — •Lukas Lührs1, Birthe Zandersons1, Norbert Huber2,1, and Jörg Weissmüller1,21Institute of Materials Physics and Technology, Hamburg University of Technology — 2Institute of Materials Research, Materials Mechanics, Helmholtz-Zentrum Geesthacht

At small length scales atomistic simulations suggest a surface-induced tension-compression asymmetry of the strength and flow stress of metallic bodies. As experimental evidence supporting this notion remains to be reported, we investigate the impact of capillary forces on small-scale plasticity.

We study the transverse plastic deformation of macroscopic nanoporous gold under uniaxial compression in electrolyte. This affords in situ variation of the surface state, specifically the surface tension, γ, during plastic flow. We find that decreasing γ results in an increase of the macroscopic plastic Poisson’s ratio, νP. We show that γ promotes the compression while hindering tensile elongation of individual ligaments. Transverse deformation during compression of the network structure is partly caused by the stretching of ligaments oriented perpendicular to the load axis. Here, the surface-induced tension-compression asymmetry acts to reduce νP. Finite element simulations support experimental observations and confirm the significant contribution of the surface tension to small-scale plasticity.

[Nano Lett., 2017, 17 (10), 6258-6266]

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