Stickslips in steady shearing as a Siganature of Solid-Fluid transition

We report in our recent work the occurrence of shear-rate dependent stickslips as a distinctive signature of solid-fluid transition for granular flows [10.1103/PhysRevLett.126.128001]. With additional measurements on the tribology between particles, we identify the speed-dependent lubrication to be one fundamental cause for such transition, and propose a new dimensionless number as the control parameter in describing the change of behaviors. Further investigations in more generic cases, including the use of a velocity-weakening friction in numerical experiments, provide further confirmation on such picture, and allow us to visualize the development of stickslips that have not been predicted by existing theories.