Plasticity as a depinning phase transition

critical phenomena;phase transition;dislocation;plasticity;simulation;scaling;deformation;phase field crystal;discrete dislocation dynamics

Tsekenis, Georgios

关键词: critical phenomena;    phase transition;    dislocation;    plasticity;    simulation;    scaling;    deformation;    phase field crystal;    discrete dislocation dynamics;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/35323/TSEKENIS-DISSERTATION.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

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 dislocationdynamics (DDD) model and a phaseeld 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 interactionsand 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 extractthenite-size scaling properties of the slip-avalanche statistics, going beyond gross aggregate statistics ofslip 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 themeaneld 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 stressgrows with the square root of the dislocation density (Taylor's relation). Consequently, dislocations jam atany density, in contrast to granular materials, which only jam above a critical density.Finally, we utilize a phaseeld crystal model to extract the size, energy and duration distributions ofthe avalanches and show that they exhibit power law behavior in agreement with the meaneld interfacedepinning universality class.