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Hengxu Song1 2 Stefanos Papanikolaou2 1

1, Johns Hopkins University, Baltimore, Maryland, United States
2, West Virginia University, Morgantown, West Virginia, United States

Uniaxial compression/tension at small scales can be carried out using either load control or displacement control, both are commonly used in experimental and theoretical (simulation) studies.
While it is typically suggested that loading protocols should not influence the mechanical properties, this assumption may be violated at the nanoscale due to the emergence of size effects and abrupt strain bursts.
Here, we report a theoretical study carried out through two dimensional discrete dislocation dynamics simulations, showing that two loading protocols indeed have different effects on flow stress and plastic events statistics during uniaxial compression of thin films or pillars. The combination of nanoscale size effects and dislocation drag strain-rate effects provide a complex connection between load control at low rates with displacement control at high rates. Through scaling analysis, we demonstrate how to build a correspondence between load and displacement control at various rates and sizes. Our main focus is on the flow stress and plastic flow stress noise statistics, however our method is generalizable to other measurable quantities.

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