报告题目：新材料和新结构在概率尾部的强度最大化设计：一个被忽视的准脆性材

料和仿生材料挑战 Design of New Materials and Structures to Maximize

Strength at Probability Tail: A Neglected Challenge for Quasibrittle and

Biomimetic

Materials报告时间：2018年10月30日15:00－17:00报告地点：7号楼二楼报告厅报

告 人：Zdenek P.

Bažant（美国科学院、工程院以及艺术科学院三院院士，铁木辛科奖章获得者，西北大学教授）欢迎广大师生参加土木与交通学院2018年10月26日报告人简介：Zdenek

P. Bažant was born and educated in Prague (Ph.D. 1963), Bažant joined

Northwestern in 1969, where he has been W.P. Murphy Professor since 1990

and simultaneously McCormick Institute Professor since 2002, and

Director of Center for Geomaterials . He was inducted to NAS, NAE, Am.

Acad. of Arts & Sci., Royal Soc. London; to the academies of Italy ,

Austria, Spain, Czech Rep., India.and Lombardy; to Academia Europaea,

Eur. Acad. of Sci. & Arts. Honorary Member of: ASCE, ASME, ACI, RILEM;

received 7 honorary doctorates (Prague, Karlsruhe, Colorado, Milan,

Lyon, Vienna, Ohio State); Austrian Cross of Honor for Science and Art

1stClass from President of Austria; ASME Medal, ASME Timoshenko, Nadai

and Warner Medals; ASCE von Karman, Freudenthal, Newmark, Biot, Mindlin

and Croes Medals and Lifetime Achievement Award; SES Prager Medal; RILEM

L’Hermite Medal; Exner Medal ; Torroja Medal ; etc. He authored eight

books: Scaling of Structural Strength, Inelastic Analysis, Fracture &

Size Effect, Stability of Structures, Concrete at High Temperatures,

Concrete Creep and Probabilistic Quasibrittle Strength. H-index: 121,

citations: 66,000 (on Google, incl. self-cit.), i10 index: 605. In 2015,

ASCE established ZP Bažant Medal for Failure and Damage Prevention. He

is one of the original top 100 ISI Highly Cited Scientists in Engrg.

(www.ISIhighlycited.com). His 1959 mass-produced patent of safety ski

binding is exhibited in New England Ski Museum.Home:

developing new

materials, the research objective has been to maximize the mean strength

(or fracture energy) of material or structure and minimize the

coefficient of variation. However, for engineering structures such as

airframes, bridges of microelectronic devices, the objective should be

to maximize the tail probability strength, which is defined as the

strength corresponding to failure probability 10-6 per lifetime.

Optimizing the strength and coefficient of variation does not guarantee

it. The ratio of the distance of the tail point from the mean strength

to the standard deviation depends on the architecture and microstructure

of the material (governing the safety factor) is what should also be

minimized. For the Gaussian and Weibull distributions of strength, the

only ones known up to the 1980s, this ratio differs by almost 2:1. For

the strength distributions of quasibrittle materials, it can be anywhere

in between, depending on material architecture and structure size. These

materials, characterized by a nonnegligible size of the fracture process

zone, include concretes, rocks, tough ceramics, fiber composites, stiff

soils, sea ice, snow slabs, rigid foams, bone, dental materials, many

bio-materials and most materials on the micrometer scale. A theory to

deduce the strength distribution tail from atomistic crack jumps and

Kramer’s rule of transition rate theory, and determine analytically the

multiscale transition to the representative volume element of material,

is briefly reviewed. The strength distribution of quasibrittle

particulate or fibrous materials, whose size is proportional to the

number of RVEs, is obtained from the weakest-link chain with a finite

number of links, and is characterized by a Gauss-Weibull grafted

distribution. Close agreement with the observed strength histograms and

size effect curves are demonstrated. Discussion then turns to new

results on biomimetic imbricated (or scattered) lamellar systems,

exemplified by nacre, whose mean strength exceeds the strength of

constituents by an order of magnitude. The nacreous quasibrittle

material is simplified as a fishnet pulled diagonally, which is shown to

be amenable to an analytical solution of the strength probability

distribution. The solution is verified by million Monte-Carlo

simulations for each of fishnets of various shapes and sizes. In

addition to the weakest-link model and the fiber-bundle model, the

fishnet is shown to be the third strength probability model that is

amenable to an analytical solution. It is found that, aside from its

well-known benefit for the mean strength, the nacreous microstructure

provides a significant additional strengthening at the strength

probability tail. Finally it is emphasized that the most important

consequence of the quasibrittleness, and also the most effective way of

calibrating the tail, is the size effect on mean structural strength.

题 目：Non-local and Non-classical Continuum Models

**附件：**无

时 间：2018年3月5日10:00-12:00

地 点：交通大楼604会议室

报告人：J.N. Reddy（美国德州农工大学，教授，美国工程院院士）

欢迎广大师生参加

土木与交通学院

2018年3月1日

报告人简介：

Dr. Reddy, the Oscar S Wyatt Endowed Chair Professor, Distinguished

Professor, and Regents Professor of Mechanical Engineering at Texas A&M

University, is a highly-cited researcher, author of 21 textbooks and

over 600 journal papers, and a leader in the applied mechanics field for

more than 40 years. Dr. Reddy has been a member of Texas A&M faculty

since 1992.