Plastic Poisson’s Ratio of Nanoporous Metals: A Macroscopic Signature of Tension–Compression Asymmetry at the Nanoscale,Nano Letters

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Plastic Poisson’s Ratio of Nanoporous Metals: A Macroscopic Signature of Tension–Compression Asymmetry at the Nanoscale
Nano Letters ( IF 9.6 ) Pub Date : 2017-09-21 00:00:00 , DOI: 10.1021/acs.nanolett.7b02950
Lukas Lührs ₁ , Birthe Zandersons ₁ , Norbert Huber _{1,

2} , Jörg Weissmüller _{1,

2}

Affiliation

The suggestion, based on atomistic simulation, of a surface-induced tension−compression asymmetry of the strength and flow stress of small metal bodies so far lacks experimental confirmation. Here, we present the missing experimental evidence. We study the transverse plastic flow of nanoporous gold under uniaxial compression. Performing mechanical tests in electrolyte affords control over the surface state. Specifically, the surface tension, γ, can be varied in situ during plastic flow. We find that decreasing γ leads to an increase of the effective macroscopic plastic Poisson ratio, ν_P. Finite element simulations of a network with surface tension confirm the notion that ν_P of nanoporous gold provides a signature for a local tension–compression asymmetry of the nanoscale struts that form the network. We show that γ promotes compression while impeding tensile elongation. Because the transverse strain is partly carried by the elongation of ligaments oriented normal to the load axis, the surface-induced tension–compression asymmetry acts to reduce ν_P. Our experiment confirms a decisive contribution of the surface tension to small-scale plasticity.

中文翻译：

纳米多孔金属的塑性泊松比：纳米级拉伸压缩不对称的宏观特征

到目前为止，基于原子模拟的关于小金属物体的强度和流动应力的表面诱导的拉伸-压缩不对称性的建议尚缺乏实验证实。在这里，我们介绍了缺少的实验证据。我们研究了单轴压缩下纳米多孔金的横向塑性流动。在电解液中进行机械测试可控制表面状态。具体而言，在塑料流动过程中，表面张力γ可以在原位变化。我们发现，减少γ导致增加有效的宏观塑性泊松比，ν的_P。用表面张力确认的概念，即一个网络的有限元模拟ν _P纳米多孔金的形成为形成网络的纳米级支杆的局部拉压不对称性提供了标志。我们表明，γ促进压缩同时阻碍拉伸伸长率。因为横向应变部分地被取向为垂直于负载轴韧带的伸长进行，表面诱导的拉伸-压缩不对称起到减少ν _P。我们的实验证实了表面张力对小规模可塑性的决定性贡献。

更新日期：2017-09-21

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