Evolution of Interfacial Mechanical Properties With Temperature

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Nanoscale Mechanics at the Crossroads of
Technological Breakthrough
N. Chandra Department of Mechanical
Engineering FAMU-FSU College of
Engineering Florida State University Tallahassee,
FL 32312
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Length Scale From Universe to Atom
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Length Scale From Universe to Atom, contd.
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Length Scale From Universe to Atom, contd.
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Length Scale From Universe to Atom, contd.
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Length Scale From Universe to Atom, contd.
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Length Scale From Universe to Atom, contd.
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Capability of Nanotechnology

Source NASA Ames
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Milestone of Mechanics
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Milestone of Mechanics, contd.
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Milestone of Mechanics, contd.
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Milestone of Mechanics, contd.
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Grain Boundary sliding

An example of mechanics at nanoscale affecting
behavior at macro scale
Energetics of sliding dependant on the applied
boundary conditions (Chandra and Dang 1999)
. Magnitude of sliding depends on grain boundary
energy which in turn depends on the atomic
structure of grain boundary, impurity atoms etc.
(Namilae, Chandra and Nieh, 2001)
Magnitude of Grain boundary sliding and energy
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Grain Boundary sliding, contd.

• Mg atoms in Al grain boundary increase grain
  boundary energy
• which again increases the tendency for grain
  boundary sliding.
• Positions at which Mg atoms are stable
  determined by atomic
• level stresses.
• This effect can be at least qualitatively
  explained using Eshelby
• concept and pressure experienced by Mg atom.

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Where are we headed?
While continuum mechanics attempts to solve
pdes, molecular dynamics uses multi body
dynamics (similar to the earliest planetary
mechanics). Energy of the system is the common
denominator in both the approaches. Are continuum
concepts valid at atomic scales? If so, how do we
define them. Should we even care about continuum
concepts? If not what are the new quantities? How
do we define non-conservative motion (inelastic
energy as opposed to potential functions?