Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session G47: Invited Session: Elasticity and Plasticity Outside of Equilibrium: Modeling From Micro to Meso Scales |
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Sponsoring Units: GSNP Chair: Zhi Feng Huang, Wayne State University Room: Hilton Baltimore Holiday Ballroom 6 |
Tuesday, March 19, 2013 11:15AM - 11:51AM |
G47.00001: Dislocation dynamics, plasticity and avalanche statistics using the phase-field crystal model Invited Speaker: Luiza Angheluta The plastic deformation of stressed crystalline materials is characterized by intermittency and scaling behavior. The sudden strain bursts arise from collective interactions between depinned crystal defects such as dislocations. Recent experiments on sheared nanocrystals provide insights into the connection between the crystal plasticity and the mean field theory of the depinning transition, based on the similar power-law statistics of avalanche events. However, a complete theoretical formulation of this connection is still lacking, as are high quality numerical data. Phase field crystal modelling provides an efficient numerical approach to simulating the dynamics of dislocations in plastic flows at finite temperature. Dislocations are naturally created as defects in a periodic ground state that is being sheared, without any ad hoc creation and annihilation rules. These crystal defects interact and annihilate with one another, generating a collective effect of avalanches in the global plastic strain rate. We examine the statistics of plastic avalanches both at finite and zero temperatures, and find good agreement with the predictions of the mean field interface depinning theory. Moreover, we predict universal scaling forms for the extreme statistics of avalanches and universal relations between the power-law exponents of avalanche duration, size and extreme value. These results account for the observed power-law distribution of the maximum amplitudes in acoustic emission experiments of crystal plasticity, but are also broadly applicable to other systems in the mean-field interface depinning universality class, ranging from magnets to earthquakes. The work reported here was performed in collaboration with: Georgios Tsekenis, Michael LeBlanc, Patrick Y Chan, Jon Dantzig, Karin Dahmen, and Nigel Goldenfeld. [Preview Abstract] |
Tuesday, March 19, 2013 11:51AM - 12:27PM |
G47.00002: Connecting grain boundary properties to microstructural evolution in polycrystalline metals Invited Speaker: Elizabeth Holm Within the last decade, both computational and experimental methods have evolved to the point that large-scale surveys of grain boundary properties have become tractable. Such studies have provided new information and insight about boundary structure, energetics, motion mechanisms, and mobility on a scale that invites application to polycrystalline systems. However, the complex behavior revealed in these studies often generates as many questions as it answers. This presentation will review pertinent computational and experimental studies of grain boundary properties in FCC metals, concentrating on boundary energy and mobility. The goal will be to identify the microstructural signatures of boundary properties in polycrystalline grain boundary networks. Topics will include how boundary energy and mobility trends manifest in real microstructures; the effects of shear coupling on boundary motion in bicrystals and polycrystals; the significance of boundaries that move in a non-thermally-activated manner to low temperature grain growth; and the consequences of the thermal roughening transition on grain stagnation. In each case, individual grain boundary properties couple with the characteristics of the grain boundary network to generate diverse microstructural outcomes. [Preview Abstract] |
Tuesday, March 19, 2013 12:27PM - 1:03PM |
G47.00003: Modeling polycrystalline multiferroics materials Invited Speaker: Ken Elder Multifeorroics are materials that involve the coupling of elasticity, magnetization and polarization. The ability to turn mechanical energy into electric or magnetic energy has been exploited for many years in device applications. More recently there has been a great deal of interest in systems that contain all three properties so that the elastic coupling can be used to control polarization with magnetic fields or magnetization with electric fields. In this talk I would like to discuss the development of a phase field crystal model that incorporates all of the rich physics contained in polycrystalline multiferroic materials. To extend the use of this model to larger length scales an amplitude description will be presented. This description also provides a natural link to traditional continuum field theories of multiferroic materials. [Preview Abstract] |
Tuesday, March 19, 2013 1:03PM - 1:39PM |
G47.00004: Phase-Field Crystal Modeling of Polcrystalline Pattern Evolution in Hard and Soft Matter Invited Speaker: Alain Karma The phase-field crystal (PFC) model has attracted considerable attention during the past decade for its potential application to model the complex defect-mediated dynamics of hard and soft crystalline materials on diffusive time scales. The model is rooted in earlier models of non-equilibrium pattern formation (Swift-Hohenberg equation), and classical density functional theory that expresses the free-energy of a system as a functional of its density. This talk will discuss progress made to investigate the dynamics for both isolated grain boundaries and complex polycrystalline patterns under the driving forces of boundary curvature and applied stress. The results highlight fundamental differences between polycrystalline pattern evolution in soft matter, including colloid crystals and crystalline non-equilibrium patterns described by the standard PFC dynamics, and crystalline solids described by a reformulation of this dynamics presented in this talk. The results also pave the way for a unified theory of polycrystalline pattern evolution in hard and soft matter. [Preview Abstract] |
Tuesday, March 19, 2013 1:39PM - 2:15PM |
G47.00005: Understanding the Evolution of Microstructure: What is the Role of Molecular Dynamics? Invited Speaker: Stephen Foiles The microstructure of a material, as characterized for example by grain size, determines a wide range of materials properties such as strength, toughness, and corrosion resistance. Understanding how the microstructure influences properties and how to obtain a desired microstructure are some of the enduring central problems of materials science. This challenge is inherently multi-scale since the fundamental mechanisms by which microstructures change occur at the atomic scale while the network of interfaces is on a scale of microns and up. In this talk, the role of molecular dynamics (MD) simulations in understanding the evolution of microstructure will be examined. The successes and outstanding challenges of using MD simulations to determine the properties of grain boundaries, in particular free energy and mobility, will be described. Further, microstructures with nanoscale grains evolve in times accessible to MD simulation. The insights into grain growth and deformation that can be obtained from such simulations will be described. [Preview Abstract] |
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