Statistics of slip avalanches in sheared amorphous materials based on atomistic simulation

Zhang, Dansong

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https://hdl.handle.net/2142/50407 Copy

Description

Title

Statistics of slip avalanches in sheared amorphous materials based on atomistic simulation

Author(s)

Zhang, Dansong

Issue Date

2014-09-16

Director of Research (if dissertation) or Advisor (if thesis)

• Ostoja-Starzewski, Martin
• Dahmen, Karin A.

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• amorphous plasticity
• slip avalanches
• atomistic simulation
• power-law
• scaling
• subextensive

Abstract

Many experiments have found that amorphous materials deform via slip avalanches in the plastic regime, which are bursts of plastic flows and show scale free features, as evidenced by a power-law probability distribution of the magnitude of serrations in stress-strain curves. Mesoscale models of amorphous plasticity, depending on assumptions of the interaction between slipped sites, give different predictions of scaling exponents. Atomistic simulation, which does not rely on such assumptions, offers an important approach to a profound understanding of this phenomenon. In this study, we simulate the quasi-static simple shear deformation of 2D amorphous samples with an atomistic approach. Tracking the evolution of stress and potential energy with strain, we find that each avalanche event is marked by a sudden drop in shear stress and potential energy. The relationship between stress drop and energy drop becomes asymptotically linear for increasing avalanche sizes. The probability distributions of stress drops follow a power law, with an exponent of 1.16 ± 0.05. Scaling of the distributions for different system sizes reveals that the maximum avalanche size and the number of events of a given avalanche size scale subextensively with system size, consistent with previous studies. Moreover, the spatial extent of avalanches is measured. It is found that the occurrence of each avalanche is marked by a sudden localization of deformation. Large avalanche events are generally more delocalized than small events, as slips are triggered in broader regions. However, the plastic deformation is still subextensive, not extensive, even for the largest avalanches.

Graduation Semester

2014-08

Permalink

http://hdl.handle.net/2142/50407

Copyright and License Information

Copyright 2014 Dansong Zhang

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