报告题目：Microbridge Tests
报告人：Prof. Tongyi Zhang (张统一)
报告时间：
报告地点：569vip威尼斯游戏玉泉校区教12-118
报告摘要：
In the present work, we summarize the novel microbridge testing method for mechanical characterization of thin films including single-layer, bilayer, trilayer, and multilayer thin films. The samples for microbridge tests were prepared with the microelectromechanical fabrication technique such that they were easy to be handled with. The microbridge tests were conducted with a load and displacement sensing nanoindenter system equipped with a microwedge probe. The length of the microwedge probe is larger than the width of microbridge samples, which makes one-dimensional analysis appropriate. In mechanics analysis, we modeled the substrate deformation with three coupled springs and considered residual stress in each layer, thereby resulting in a closed-form formula of deflection versus load. The microbridge testing method allows us to simultaneously evaluate the Young’s modulus, residual stress and bending fracture strength of single-layer films from an experimental load-deflection curve. The mechanics analysis shows that four parameters, bending stiffness, tensile stiffness, residual resultant force and residual moment, determine the bending behavior of a multilayer beam including the initial deflection caused only by residual moment and residual resultant force without any applied loads. An experimental procedure was developed to determine the four parameters. In addition to the characterization of elastic behaviors of thin films, the microbridge test has been extended to investigate the plastic behavior of thin films. Examples to demonstrate the developed microbridge test will be illustrated on single-layer, bilayer and trilayer films. The microbridge test is further developed to the nanobridge test, in which the adhesion between the probe and a tested nanowire must be considered.
报告人简介：
张统一教授是我国自己培养、在香港科技大学成长的学者。他于1982年和1985年在北京科技大学材料物理专业获硕士和博士学位。毕业后获得德国洪堡基金会奖学金，1986—1988年在德国哥廷根大学任研究员。1988—1990年在美国罗彻斯特大学进行博士后研究。1990—1993年在美国耶鲁大学任副研究员。1993年到香港科技大学任教至今，目前是该校讲座教授。研究领域包括铁电与压电材料的多场断裂力学、微纳观力学和氢渗透与氢致开裂。他是2007年度国家自然科学二等奖第一获奖人（共四位获奖人）和1987年度自然科学二等奖第三获奖人（共十位获奖人）。2003年获香港裘槎高级研究学者奖，2001年获美国ASM International Fellow Award，1988年获中国科学技术协会青年科技奖。他发表139篇SCI学术论文。5次收到Web of Science贺卡，祝贺他的“文章引用率在所从事领域位于1％前列，工作在领域里有重大的影响力”。截至2009年3月30日，他的论文SCI他引次数为1776次；其中在香港科技大学完成的4篇学术论文SCI他引次数为234、169、119和117次。获得2项美国专利。在国际和国内学术会议上作特邀、主题和大会报告32次，并将在第12届国际断裂大会上作大会报告。组织和参与组织包括第八届国际断裂基础大会在内的3次国际会议。为国际和国内学报编辑了八期特刊。
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