How things slide : friction is fracture
Orateur : Jay Fineberg
The Racah Institute of Physics, The Hebrew University of Jerusalem, Givat Ram, Jerusalem Israel
Résumé : The dynamics of how two rough frictional interfaces start to slide is a fundamental question in fields ranging from material science to geophysics. On the one hand, from the time of Da Vinci the onset of frictional motion is thought to be characterized by the static friction coefficient that couples two materials. For hundreds of years, this has been considered to be a material constant. On the other hand, the same processes that give rise to the onset of frictional motion also cause earthquakes, when tectonic plates locked together by friction start to slip. We describe new experiments that examine how rapid crack-like processes that fracture a frictional interface cause the onset of macroscopic motion that we know as frictional sliding. Results of this study are surprising. We demonstrate that a number of different types of earthquakes exist and that the existing paradigm for understanding friction, namely a "static friction coefficient", is not a material constant at all, but is intimately related to the details of how forces are applied to a system. We then show that our experiments suggest a new paradigm for understanding friction ; that friction is actually a fracture process or, in other words, the question of "How things slide" is basically the same as "How things break" !
Date et lieu : Vendredi 20 Février 2015, amphithéâtre IUSTI, à 14h