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Micro-
and Nano-Mechanics of Surface Contact Plasticity
The science-based methodologies we introduce students to first should
be those that provide for tackling the broadest possible classes of
problems. In this seminar I will review some of the historical
antecedents that underlie most of our current undergraduate
science-based curricula and then, as an example, introduce a means of
introducing basic mechanics in a way that gives students access to a
very broad class of problems of professional interest. As a
demonstration that these methods can be used to solve problems of
significant professional interest, I will show an application to the
dynamics of a spinning satellite with long radial wire appendages.
Rough surface contact
plasticity at microscale and nanoscale is of crucial importance in
many new applic at ions and technologies, such as nano-imprinting and
nano-welding. The multiscale n at ure of surface roughness, the
structural and size-sensitive m at erial deform at ion behavior, and
the importance of surface forces and other physical interactions give
rise to very complex surface phenomena at small scales. We first show
the p at hological behaviors of contact models based on fractal
roughness and continuum plasticity theory. A micromechanical model of
surface steps under adhesive contact examines disloc at ion nucle at
ion from surface sources and disloc at ion interaction underne at h.
The disloc at ion nucle at ion process is studied by both at omistic
simul at ions and the Rice-Thomson model. Depending on interface
adhesion, roughness fe at ures and slip planes, we have a variety of
surface deform at ion behaviors, such as anisotropic hardening and l
at ent softening. As a consequence, the rough surface contact at
mesoscale leads to the form at ion of a disloc at ion double layer,
which cannot be predicted by existing continuum and nonlocal
plasticity theories. The micromechanical analysis of surface
plasticity could serve as the connection between microscale bulk
disloc at ion plasticity and nanoscale at omistic simul at ions
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