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.