Statics and dynamics of folding in three dimensional elasticity
时间： 2017-08-22 来源： 信息员
应国际应用力学中心、航天航空学院刘子顺教授的邀请，意大利特兰托大学(University of Trento, Italy) Davide Bigoni教授及一行(Prof. Piccolroaz and Dr Misseroni) 将来我校进行学术交流。
报告题目：Statics and dynamics of folding in three dimensional elasticity
Professor Davide Bigoni is a mechanician working in material modelling (nonlinear elasticity, damage, elastoplasticity, visco and thermo- plasticity, with applications to ceramic materials, granular media, composites, metals, and biomaterials), wave propagation in solids (with applications to metamaterials), fracture mechanics (with applications to porous media, and rocklike materials) and structural mechanics (with an emphasis on bifurcation and instability). His approach to research is the employment of a broad vision of mechanics, with a combination of mathematical modelling, numerical simulation, and experimental validation. He has been awarded an ERC advanced grant in 2013, the maximum recognition for excellence in research in Europe, awarded by the European Research Council. From 2001 Davide Bigoni holds a full professor position at the University of Trento (Italy), where he is leading a very active group in the field of Solid and Structural Mechanics. He has authored or co-authored more than 100 journal papers and has published a book on nonlinear Solid Mechanics. He was elected in 2009 Euromech Fellow (of the European Mechanics Society), has received in 2012 the Ceramic Technology Transfer Day Award (of the ACIMAC and ISTEC-CNR), in 2014 he has received the Doctor Honoris Causa degree at the Ovidius University of Constanta, and in 2016 the Panetti-Ferrari award from the Turin Academy of Science. He is co-editor of the Journal of Mechanics of Materials and Structures, is associate Editor of Mechanics Research Communications. He was vice chair of the panel PE8 for the European Research Council Starting Grants and panel member for the Swiss National Science Foundation Starting Grants and for the Excellence Initiative funded by the Government of Spain.
Folding is a process in which bending localizes into sharp corners separated by almost undeformed elements. This process is rarely encountered in nature and is difficult to be described within the realm of the Cauchy theory of elasticity. On the other hand, it is shown that folding can be understood as a constitutive instability of a constrained-Cosserat elastic material occurring at the elliptic boundary. The Green functions for applied concentrated force and moment are obtained for Cosserat elastic solids with extreme anisotropy, which can be tailored to bring the material in a state close to an instability threshold such as failure of ellipticity. It is shown that the wave propagation condition (and not ellipticity) governs the behavior of the Green functions. These Green functions are used as perturbing agents to demonstrate in an extreme material the emergence of localized (single and cross) stress channelling and the emergence of localized folding (or creasing, or weak elastostatic shock) and faulting (or elastostatic shock) of a Cosserat continuum, phenomena which remain excluded for a Cauchy elastic material. During folding some components of the displacement gradient suffer a finite jump, whereas during faulting the displacement itself displays a finite discontinuity.