Grains Friction and Faults
The sliding of contacting surfaces
is a formidable problem.
Friction and granular mechanics play a key
role in nature and industry, with many applications in
micro-mechanics, statistical physics, and geophysics. Granular
physics is important in a variety of different situations,
including lubrication and the behavior of dry or wet debris.
Despite the common root to many problems
in friction and granular materials,
knowledge is generally highly specialized and
intercommunication between different fields is often limited. Many
topics have received considerable study in the context of
technological systems. However recent advances by researchers in
physics, mechanics, materials science, seismology, and geophysics
are not often communicated across disciplines. Advances in the
many related sub-fields often profit from similar theoretical and
numerical approaches, although these can take different forms in
different fields. As an example, statistical approaches seem at
present limited to the tectonic scale; intermittence and
fluctuations take place at human time and length scales. It seems
therefore that scarcity of statistical investigations of friction
and grain dynamics is due to purely anthropological reasons.
Between microscopic and continuum length scales,
meso-scale
phenomena are fundamental
for understanding shear between material
interfaces and for particulate systems. A huge amount of
experimental and theoretical work has been devoted to modeling and
understanding the properties of microscopic defects but the
question of how microstructural properties link to the macroscopic
constitutive equations of continuum mechanics is crucial and
poorly understood.
Often the transition from discrete defects
to continuum mechanics
is accomplished by simple homogenization procedures neglecting the
complex features of the process, employing tools of continuum
mechanics to model deformations and slip, e.g. in the crust during
earthquakes, as well as the rheology of snow avalanches and
landslides. However the presence at the meso-scale of more
structural elements like surface roughness, grains, physical
phenomena occurring at surfaces, the presence of fluids, different
materials, and their combined effect on the response of the system
make the problem of bridging the associated length scales very
complex.
The goal
is to provide an opportunity for discussion and scholarly
exchange about these problems. Erice is the perfect venue.