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2016-2017学年第二学期航空航天系第九期学术讲座
发表时间:2017-06-22 阅读次数:727次

题目:Metamaterials with negative Poisson’s ratio and non-positive thermal expansion

主讲:Xin-Lin Gao Professor

主持:丁淑蓉 教授

时间:2017年6月22日(星期四)上午10:00

地点:光华楼东主楼2601室

 

教授简介

Dr. Xin-Lin Gao is currently a tenured full professor of mechanical engineering and the mechanics and manufacturing area director at Southern Methodist University, Dallas, Texas, USA. He was elected an ASME Fellow in December 2010 and selected as an expert by the Shanghai Thousand Talents Program in September 2013.

He received an M.Sc. degree in Engineering Mechanics in May 1997 and a Ph.D. degree in Mechanical Engineering (with a minor in Mathematics) in May 1998, both from the University of Wisconsin-Madison. He has conducted research in a variety of areas in mechanics and materials and has authored 116 journal papers, 3 book chapters, and 129 conference and other publications. His publications have received 4317 citations, with an h-index of 33 and an i10-index of 72 (Google Scholar) as of June 5, 2017. Two of his papers have been cited over 567 times each. He has been a PI or Co-PI of funded research projects worth about $9.6M. He has been a reviewer for 109 journals, 9 publishers and 14 funding organizations and has organized 25 symposia at major international conferences. He has been an editor/guest editor of one book, proceedings of one conference, and four special journal issues. He currently serves on the editorial boards of seven journals. 

 

内容简介

Metamaterials are engineered materials with unusual properties deriving mainly from their micro-architecture rather than composition. They have attracted increasing attention owing to their tailorable multi-functional properties that cannot be exhibited by naturally-occurring or traditionally-manufactured materials. Materials with a negative Poisson’s ratio and materials with a non-positive coefficient of thermal expansion are examples of mechanical metamaterials.

Four types of metallic metamaterials with tailorable mechanical properties are designed using bi-material star-shaped re-entrant planar lattice structures, which do not involve pins, adhesive, welding or pressure-fit joints and can be fabricated through laser-based additive manufacturing. Three length parameters, one angle parameter and three material combinations are used as adjustable design parameters to explore structure-property relations. For each type of the metamaterials, the effects of the design parameters on the Poisson’s ratio (PR), coefficient of thermal expansion (CTE), Young’s modulus and relative density are systematically investigated using unit cell-based micromechanical analyses and finite element simulations that incorporate periodic boundary conditions. It is found that the bi-material lattice structures can be tailored to obtain 3-D printable metallic metamaterials with positive, near-zero or negative PR and CTE together with an uncompromised Young’s modulus. In particular, it is shown that one type of the designed metamaterials can exhibit both a negative PR and a non-positive CTE simultaneously. These metallic metamaterials can find applications in structures or devices such as antennas and precision instruments to reduce thermomechanical stresses and extend service lives.

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