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CATEGORIES:Engineering - Mechanics and Materials Seminar Seri
es
SUMMARY:Elasticity and (dis)orders in networks and cellula
r patterns - Dr Marc Durand\, Université Paris Did
erot
DTSTART;TZID=Europe/London:20121019T140000
DTEND;TZID=Europe/London:20121019T150000
UID:TALK39477AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/39477
DESCRIPTION:Networks are heterogeneous materials whose continu
ous phase is assembled into slender objects - the
links - that are connected to each other at nodes.
\nThe macroscopic properties (elasticity\, transpo
rt\,...) of such systems crucially depend on the s
pecific arrangements of their components. In the f
irst part of this talk\, I will study the conditio
ns for existence of "optimal networks"\, i.e. isot
ropic networks with highest elastic moduli (and el
ectrical conductivity) for a given density. Using
a variational approach in an unconventional way\,
I will show that a simple set of rules can be esta
blished on the geometry and topology of the nodes
in such networks. Networks that satisfy these rule
s can effectively be built and I will provide exam
ples at two and three dimensions. The elastic modu
li (and electrical conductivity) of these optimal
networks constitute upper-bounds which compete or\
nimprove the well-known Hashin-Shtrikman bounds.\n
The second part of the talk will be devoted to the
description of disorders in two-dimensional cellu
lar patterns\, such as dry foams: the macroscopic
properties of these systems are affected by two ki
nds of disorders: the first one is the geometrical
disorder\, defined as the relative width of the d
istribution of cell sizes\, and the second one is
the topological disorder\, defined as the relative
width of the distribution of the number of sides
of a cell. I will show that in fact these two quan
tities are strongly correlated: a monodisperse foa
m contains mostly hexagonal cells\, while in a pol
ydisperse foam\, larger bubbles have more sides. A
model\, based on the formalism of statistical mec
hanics\, has been eveloped to explain the quasi-li
near dependence of the two disorders.
LOCATION:Oatley Seminar Room\, Department of Engineering
CONTACT:Ms Helen Gardner
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