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Atomistic Simulations of Strain Rate Dependent Deformation Behavior at Continuum Timescales

Published online by Cambridge University Press:  26 July 2012

Vikas Tomar
Vikas Tomar*
Affiliation:
vikas_tomar@nd.edu, University of Notre Dame, Arospace and Mechanical Engineering, 376 Fitzpatrick Hall, Notre Dame, IN, 46556, United States, 001-574-631-7826, 001-574-631-8341
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Abstract

A majority of computational mechanical analyses of nanocrystalline materials or nanowires have been carried out using classical molecular dynamics (MD). Due to the fundamental reason that the MD simulations must resolve atomic level vibrations, they cannot be carried out at the timescale of the order of microseconds. Additionally, MD simulations have to be carried out at very high loading rates (∼108 s−1) rarely observed in experiments. In this investigation, a modified Hybrid Monte Carlo (HMC) method that can be used to analyze time-dependent (strain rate dependent) atomistic mechanical deformation of nanostructures at continuum timescales is established. In this method there is no restriction on the size of MD timestep except that it must be such that to ensure a reasonable acceptance rate between consecutive Monte-Carlo (MC) time-steps. For the purpose of comparison HMC analyses of Cu nanowires deformation at two different strain rates (108 s−1 and 109 s−1) (each with three different timesteps 2 fs, 4fs, and 8 fs) are compared with the analyses based on MD simulations at the same strain rates and a MD timestep of 2 fs. As expected, the defect formation is found to be strain rate dependent. In addition, HMC with timestep of 8 fs correctly reproduces defect formation and stress-strain response observed in the case of MD with 2 fs (for the interatomic potential used 2 fs is the highest MD timestep). Simulation time analyses show that by using HMC a saving of the order of 4 can be achieved bringing the atomistic analyses closer to the continuum timescales.

Keywords

nanoscalesimulationnanostructure
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 976: Symposium EE – Size Effects in the Deformation of Materials – Experiments and Modeling , 2006 , 0976-EE01-05
Copyright
Copyright © Materials Research Society 2007

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