Size effects and strength fluctuation in nanoscale plasticity

Wang, Wei; Zhong, Yuan; Lu, K.; Lü, Lei; McDowell, David L.; Zhu, Ting

doi:10.1016/j.actamat.2012.03.016

Cited by 36 publications

(18 citation statements)

References 34 publications

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“…The factor is due to the fact that a lower strain rate gives more opportunity for thermal nucleation of fracture at the defects. It is interesting to note that similar ideas are applicable to dislocation nucleation in plasticity 41 42 43 44 45 46 , where it has been noted that the likelihood of survival of a metallic nanopillar under stress decreases with time due to nucleation events. Our model is a ‘weakest-link' model, since we assume that the graphene sheet fractures as soon as its weakest GB/TJ defect becomes unstable.…”

Section: Resultsmentioning

confidence: 89%

Toughness and strength of nanocrystalline graphene

2016

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Pristine monocrystalline graphene is claimed to be the strongest material known with remarkable mechanical and electrical properties. However, graphene made with scalable fabrication techniques is polycrystalline and contains inherent nanoscale line and point defects—grain boundaries and grain-boundary triple junctions—that lead to significant statistical fluctuations in toughness and strength. These fluctuations become particularly pronounced for nanocrystalline graphene where the density of defects is high. Here we use large-scale simulation and continuum modelling to show that the statistical variation in toughness and strength can be understood with ‘weakest-link' statistics. We develop the first statistical theory of toughness in polycrystalline graphene, and elucidate the nanoscale origins of the grain-size dependence of its strength and toughness. Our results should lead to more reliable graphene device design, and provide a framework to interpret experimental results in a broad class of two-dimensional materials.

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Section: Resultsmentioning

confidence: 89%

Toughness and strength of nanocrystalline graphene

2016

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“…Moreover, [52] extended pop-in investigations into multiple types of pop-in modes: a primary pop-in with a large displacement excursion and a number of subsequent pop-ins with comparable and small displacement excursions. The distribution of pop-ins in single FCC crystals has also been investigated to some degree [47] for Cu single crystals, finding that the distribution can be fitted by a Gaussian with mean and variance that depend on grain orientation.…”

Section: Introductionmentioning

confidence: 99%

Discrete dislocation dynamics simulations of nanoindentation with pre-stress: Hardness and statistics of abrupt plastic events

Song

Yavaş

Giessen

et al. 2019

Journal of the Mechanics and Physics of Solids

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“…Nanomaterials and nanostructures are well known to have mechanical properties that greatly differ from that of their bulk counterparts. This includes notable examples such as strengthening mechanisms in nano-grained metals [1][2][3], multilayer nanolaminate composites with enhanced hardness [4][5][6], material size effects [7][8][9][10], and dislocation starvation and mechanical annealing phenomena [11][12][13]. These unique mechanical properties provide potential avenues for engineering nanostructures and surfaces with desirable mechanical properties, benefiting such diverse fields as micro/nano-electro-mechanical systems (MEMS/NEMS), nanotribology, and biomedical applications.…”

Section: Introductionmentioning

confidence: 99%

The effects of confined core volume on the mechanical behavior of Al/a-Si core-shell nanostructures

Fleming

Zou

2017

Acta Materialia

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The mechanical behavior of novel Al/a-Si core-shell nanostructures (CSNs) is studied using instrumented nanoindentation to investigate the role that the confined core volume plays on the mechanical response of these structures. The CSNs are fabricated from truncated hemispherical Al nanodots with 100, 200, and 300 nm base diameters, which are then conformably coated with a-Si. CSNs with the smallest core diameter, and therefore the smallest confined core volume, have a unique load-displacement behavior characterized by nearly complete recovery of deformation beyond the elastic limit, which is enabled by dislocation activities within the confined Al core. In conjunction with this deformation recovery, discontinuous indentation signatures known as "load-drops" and "load-jumps" are observed during loading and unloading, respectively. As the size of the confined core volume increases, these indentation signatures are suppressed and the deformation-resistant properties are reduced. Supporting molecular dynamics simulations show that a smaller core volume results in a larger back-stress developed in the core during indentation, which further correlates with improved dislocation removal from the core after unloading. This complementary experimental and modeling investigation provides insight into the mechanisms that contribute to the unique mechanical properties of Al/a-Si CSNs.

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Size effects and strength fluctuation in nanoscale plasticity

Cited by 36 publications

References 34 publications

Toughness and strength of nanocrystalline graphene

Toughness and strength of nanocrystalline graphene

Discrete dislocation dynamics simulations of nanoindentation with pre-stress: Hardness and statistics of abrupt plastic events

The effects of confined core volume on the mechanical behavior of Al/a-Si core-shell nanostructures

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