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CATEGORIES:Engineering Department Bio- and Micromechanics Sem
inars
SUMMARY:Theory of Elasticity at the Nanoscale - Professor
Bhushan Karihaloo\, Cardiff University
DTSTART;TZID=Europe/London:20091113T140000
DTEND;TZID=Europe/London:20091113T150000
UID:TALK20235AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/20235
DESCRIPTION:We have shown in a series of recent papers that th
e classical theory of elasticity can be extended t
o the nanoscale by supplementing the equations of
elasticity for the bulk\nmaterial with the general
ized Youngâ€“Laplace equations of surface elasticity
in order to capture the often unusual mechanical
and physical properties of nano-structured particu
late and porous materials. This talk\, based on th
e review paper Advances in Applied Mechanics (42\,
2009\, 1-68)\, will describe how this has been do
ne.\n It will begin with a description of the gen
eralized Youngâ€“Laplace equations. It will then gen
eralize the classical Eshelby formalism to nano-in
homogeneities\; the Eshelby tensor now depends on
the size of the inhomogeneity and the location of
the material point in it. Then the stress concentr
ation factor of a spherical nanovoid is calculated
\, as well as the strain fields in quantum dots (Q
Ds) with multi-shell structures and in alloyed QDs
induced by the mismatch in the lattice constants
of the atomic species.\n This will be followed by
a generalization of the micromechanical framework
for determining the effective elastic properties
and effective coefficients of thermal expansion of
heterogeneous solids containing nano-inhomogeneit
ies. It will be shown\, for example\, that the ela
stic constants of nanochannel-array materials with
a large surface area can be made to exceed those
of the nonporous matrices through pore surface mod
ification or coating. \n Finally\, the scaling la
ws governing the properties of nano-structured mat
erials are derived. The underlying cause of the si
ze dependence of these properties at the nanoscale
is the competition between surface and bulk energ
ies. These laws provide a yardstick for checking t
he accuracy of experimentally measured or numerica
lly computed properties of nano-structured materia
ls over a broad size range and can thus help repla
ce repeated and exhaustive testing by one or a few
tests.
LOCATION:Oatley Seminar Room\, Department of Engineering
CONTACT:Ms Helen Gardner
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