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13日（周四）上午10：3
讲座地点：九里校区行政楼二楼力学报告厅
讲座题目：Mesomechanics of Metallic Glasses
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 65078-65060 Fax +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：
Metallic Glasses deform plastically by stress-driven, local atomic re-arrangements. On the atomic scale, the result is a change in neighborhood relations between atoms, whereas on the mesoscale the same process can be envisaged as creation of a plastic (stress-free) eigenstrain in a small volume of typically less than 1 nm^3. These shear transformations (ST) mutually couple through internal stresses associated with the shear eigenstrain. Their occurrence is, on the mesoscale, described as the crossing of an atomic-scale energy barrier either by the work of local stresses (T=0) or by thermal activation (T>0).
In mesomechanical models we describe the material as a continuum, discreteized into finite elements with size above the ST volume. ST activation is described by a statistical spectrum of activation stresses or activation energies which may depend on pressure. Upon activation, a local eigenstrain is applied, stress re-distribution is evaluated, and sequels of the initial event that arise from the stress changes are traced. Also, due to there-arrangements occurring in the disordered atomic microstructure, the local activation parameters evolve in a stochastic manner.
As we shall show, this mesoscale dynamics naturally gives rise to deformation avalanches associated, in the spatial domain, with the emergence of micro-shear-bands. If coupled to an irreversible softening mechanism such as free volume accumulation, at some point these micro-shear bands coalesce into a catastrophic shear band indicating material failure. We investigate the avalanche dynamics, which we show to be independent on deformation mode, external boundary conditions or material parameters. We also study the phenomenon of micro-shear banding and discuss methods how to engineer the microstructure in order to delay catastrophic shear band formation.
主办：研究生院
