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Title:Plasticity as a depinning phase transition
Author(s):Tsekenis, Georgios
Director of Research:Dahmen, Karin A.
Doctoral Committee Chair(s):Hubler, Alfred W.
Doctoral Committee Member(s):Dahmen, Karin A.; Weismann, Michael; Ceperley, David M.
Department / Program:Physics
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):critical phenomena
phase transition
phase field crystal
discrete dislocation dynamics
Abstract:Crystalline materials deform in an intermittent way with slip-avalanches that are power-law distributed. In this work we study plasticity as a pinning-depinning phase transition employing a discrete dislocation dynamics (DDD) model and a phase eld crystal (PFC) model in two dimensions. Below a critical ( ow) stress, the dislocations are pinned/jammed within their glide plane due to long-range elastic interactions and the material exhibits plastic response. Above this critical stress the dislocations are mobile (the depinned/ unjammed phase) and the material constantly ows. We employ discrete dislocation dynamics to resolve the temporal pro les of slip-avalanches and extract the nite-size scaling properties of the slip-avalanche statistics, going beyond gross aggregate statistics of slip avalanche sizes. We provide a comprehensive set of scaling exponents, including the depinning exponent . Our work establishes that the dynamics of plasticity, in the absence of hardening, is consistent with the mean eld interface depinning universality class, even though there is no quenched disorder. We also use dislocation dynamics and scaling arguments in two dimensions to show that the critical stress grows with the square root of the dislocation density (Taylor's relation). Consequently, dislocations jam at any density, in contrast to granular materials, which only jam above a critical density. Finally, we utilize a phase eld crystal model to extract the size, energy and duration distributions of the avalanches and show that they exhibit power law behavior in agreement with the mean eld interface depinning universality class.
Issue Date:2012-05-22
Rights Information:Copyright 2012 Georgios Tsekenis
Date Available in IDEALS:2012-05-22
Date Deposited:2012-05

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