A Frictional Transition is not Fictional

Much of the recent studies have been motivated by the idea that a frictional transition drives these phenomena, and a theoretical framework has been proposed [1]. The rheological behavior predicted by the theory has been verified in numerical simulations [2] and experiments [3]. The experimental study reported in the recent PNAS paper by Cécile Cavaud and collaborators, “reveals” the underlying frictional transition by directly measuring the effective friction coefficient of the suspension through experiments inspired by granular physics. The results demonstrate that the macroscopic, shear thickening rheology emerges only if shear creates frictional contacts in an initially frictionless suspension.