2015/11/14 by Stefanos Papanikolaou, Papanikolaou, Stefanos, Hengxu Song +3
Engineering · Materials Science · Physics and Astronomy · #Disordered Systems and Neural Networks (cond-mat.dis-nn) #FOS: Physical sciences #Force Microscopy Techniques and Applications #Materials Science (cond-mat.mtrl-sci) #Microstructure and mechanical properties #Mineral Processing and Grinding #Soft Condensed Matter (cond-mat.soft) #Statistical Mechanics (cond-mat.stat-mech)
paper · pdf · doi:10.48550/arxiv.1511.04613
openalex publication_date 2015/11/14 · openalex created_date 2022/08/20 · openalex updated_date 2026/07/28
Mechanical deformation of nanopillars displays features that are distinctly\ndifferent from the bulk behavior of single crystals: Yield strength increases\nwith decreasing size and plastic deformation comes together with strain bursts\nor/and stress drops (depending on loading conditions) with a very strong\nsensitivity of the stochasticity character on material preparation and\nconditions. The character of the phenomenon is standing as a paradox: While\nthese bursts resemble the universal, widely independent of material conditions,\nnoise heard in bulk crystals using acoustic emission (AE) techniques, they\nstrongly emerge primarily with decreasing size and increasing strength in\nnanopillars. In this paper, we present a realistic but minimal discrete\ndislocation plasticity model for the elasto-plastic deformation of nanopillars\nthat is consistent with the main experimental observations of nano pillar\ncompression experiments and provides a clear insight to this paradox. With\nincreasing sample size, the model naturally transitions between the typical\nprogressive behavior of nanopillars to a behavior that resembles evidence for\nbulk mesoscale plasticity. The combination of consistent strengthening, large\nflow stress fluctuations and critical avalanches is only observed in the it\ndepinning regime where obstacles are much stronger than dislocation sources;\nin contrast, when dislocation source strength becomes comparable to obstacle\nbarriers, then yield strength size effects are absent but plasticity avalanche\ndynamics is strongly universal, across sample width and aspect-ratio scales.\nFinally, we elucidate the mechanism that leads to the connection between\ndepinning and size effects in our model dislocation dynamics. In this way, our\nmodel builds a way towards unifying statistical aspects of mechanical\ndeformation across scales.\n