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Ni X, Papanikolaou S, Vajente G, et al. Probing Microplasticity in Small-Scale FCC Crystals via Dynamic Mechanical Analysis. Phys Rev Lett. 2017;118(15):155501doi: 10.1103/PhysRevLett.118.155501.
Ni, X., Papanikolaou, S., Vajente, G., Adhikari, R. X., & Greer, J. R. (2017). Probing Microplasticity in Small-Scale FCC Crystals via Dynamic Mechanical Analysis. Physical review letters, 118(15), 155501. https://doi.org/10.1103/PhysRevLett.118.155501
Ni, Xiaoyue, et al. "Probing Microplasticity in Small-Scale FCC Crystals via Dynamic Mechanical Analysis." Physical review letters vol. 118,15 (2017): 155501. doi: https://doi.org/10.1103/PhysRevLett.118.155501
Ni X, Papanikolaou S, Vajente G, Adhikari RX, Greer JR. Probing Microplasticity in Small-Scale FCC Crystals via Dynamic Mechanical Analysis. Phys Rev Lett. 2017 Apr 14;118(15):155501. doi: 10.1103/PhysRevLett.118.155501. Epub 2017 Apr 14. PMID: 28452540.
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Phys Rev Lett. 2017 Apr 14;118(15):155501. doi: 10.1103/PhysRevLett.118.155501. Epub 2017 Apr 14.

Probing Microplasticity in Small-Scale FCC Crystals via Dynamic Mechanical Analysis.

Physical review letters

Xiaoyue Ni, Stefanos Papanikolaou, Gabriele Vajente, Rana X Adhikari, Julia R Greer

Affiliations

  1. Division of Engineering and Applied Sciences, California Institute of Technology, Pasadena, California 91125, USA.
  2. Department of Mechanical Engineering, Johns Hopkins University, 3400 N Charles St, Baltimore, Maryland 21218, USA.
  3. Department of Mechanical and Aerospace Engineering, West Virginia University, 395 Evansdale Dr, Morgantown, West Virginia 26506, USA.
  4. Department of Physics, West Virginia University, 135 Willey St, Morgantown, West Virginia 26506, USA.
  5. LIGO Laboratory, California Institute of Technology, Pasadena, California 91125, USA.

PMID: 28452540 DOI: 10.1103/PhysRevLett.118.155501

Abstract

In small-scale metallic systems, collective dislocation activity has been correlated with size effects in strength and with a steplike plastic response under uniaxial compression and tension. Yielding and plastic flow in these samples is often accompanied by the emergence of multiple dislocation avalanches. Dislocations might be active preyield, but their activity typically cannot be discerned because of the inherent instrumental noise in detecting equipment. We apply alternate current load perturbations via dynamic mechanical analysis during quasistatic uniaxial compression experiments on single crystalline Cu nanopillars with diameters of 500 nm and compute dynamic moduli at frequencies 0.1, 0.3, 1, and 10 Hz under progressively higher static loads until yielding. By tracking the collective aspects of the oscillatory stress-strain-time series in multiple samples, we observe an evolving dissipative component of the dislocation network response that signifies the transition from elastic behavior to dislocation avalanches in the globally preyield regime. We postulate that microplasticity, which is associated with the combination of dislocation avalanches and slow viscoplastic relaxations, is the cause of the dependency of dynamic modulus on the driving rate and the quasistatic stress. We construct a continuum mesoscopic dislocation dynamics model to compute the frequency response of stress over strain and obtain a consistent agreement with experimental observations. The results of our experiments and simulations present a pathway to discern and quantify correlated dislocation activity in the preyield regime of deforming crystals.

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