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创源大讲堂】Challenges in dislocation plasticity
作者:周杰    发布时间:2017-04-12 17:36:19    访问次数:1727  
 

西南交通大学“创源”大讲堂研究生学术讲座

讲座时间: 2017年4月17日(周一),4月21(周五),上午10:30

讲座地点:九里校区行政楼二楼力学报告厅

讲座题目:Challenges in dislocation plasticity

主 讲 人:Prof. Dr. Michael Zaiser

(Chair of Materials Simulation Department of Materials Science University of Erlangen-Nuremberg

Dr.-Mack-Strasse 77, 90762 Fürth, Germany,Tel. +49 911 65078-65060Fax  +49 911 65078-65066

http://www.matsim.techfak.uni-erlangen.de/

个人简介:Zaiser教授现任德国埃尔朗根-纽伦堡大学材料模拟首席教授(Chair Professor)、材料模拟研究所所长,是材料基础理论及仿真模拟研究领域的杰出科学家。主要研究工作领域是微纳米材料力学及高性能材料,通过仿真模拟手段将统计物理、材料科学、固体力学方法结合起来,对材料的微结构和缺陷的无序性和随机性及对其材料宏观力学性能的影响进行分析、解释和预测,探索提高材料力学性能的途径,指导先进材料的设计和制备。Zaiser教授在科研上有丰硕的成果,在Science、Physical Review Letters等国际一流期刊发表SCI论文160余篇,累计引用高达3700余次,其中2007年和2008年连续两次在Science上发表关于材料塑性理论和应用的重要论文,获得了学术界的高度评价。

讲座内容

This lecture series addresses some current issues in dislocation based modelling of crystal plasticity.

Lecture 1: Discrete to continuum modelling of dislocation transport.

Crystal plastic flow occurs by motion of dislocations and thus depends on dislocation microstructure. To model dislocation microstructure evolution we thus need to describe how dislocations move in space. Discrete dislocation dynamics does this by moving dislocation lines in space, but is restricted to small strains, comparatively small systems and, for reasons explained in Lecture 2, to strain rates that are unrealistically high for most engineering or processing applications. Here we discuss how we can, stating from discrete dislocation dynamics, a continuum formulation of dislocation dynamics which is tantamount to developing a hydrodynamics of curved lines. We address fundamental steps towards a kinetic formulation of dislocation dynamics and explain how to obtain the thermodynamic forces driving dislocation flow on the microstructure level.

Lecture 2: Deterministic to stochastic modelling of crystal plasticity.

We discuss fluctuation phenomena in dislocation plasticity. On the level of single dislocations, we demonstrate that motion of dislocations is extremely jerky, to the extent that deformation tests carried out at standard laboratory strain rates are virtually impossible to model on the discrete dislocation level because of the incredible numerical stiffness of the collective dynamics. On the level of collective phenomena demonstrate that dislocation motion occurs in avalanches with a wide size spectrum. We discuss fluctuation phenomena in deformation of small systems and illustrate spatial signatures of the temporal dynamics of dislocations. Finally we discuss the question how the intrinsically stochastic nature of dislocation flow relates to typical plasticity models which are, of course, deterministic: Under which conditions does stochasticity matter, and when is it ultimately irrelevant to the engineer?

主办:研究生院

 
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