Constant rate shearing on two dimensional cohesive disks

TL;DR

This study uses 2D molecular dynamics simulations to investigate stick-slip behavior in cohesive disks under constant shear, revealing periodic force fluctuations above a certain shearing rate.

Contribution

It introduces a novel 2D shearing geometry and demonstrates the emergence of stick-slip phenomena in cohesive disks under constant shear velocity.

Findings

Force measurements show periodic behavior at high shearing rates.

Disks exhibit collective displacements correlated with shear stress cycles.

Stick-slip-like behavior occurs despite constant shearing velocity.

Abstract

We performed two-dimensional Molecular Dynamics simulations of cohesive disks under shear. The cohesion between the disks is added by the action of springs between very next neighbouring disks, modelling capillary forces. The geometry of the cell allows disk-disk shearing and not disk-cell wall shearing as it is commonly found in literature. Does a stick-slip phenomenon happen though the upper cover moves at a constant velocity, i.e. with an infinite shearing force? We measured the forces acted by the disks on the upper cover for different shearing rates, as well as the disk velocities as a function of the distance to the bottom of the cell. It appears that the forces measured versus time present a periodic behavior,very close to a stick slip phenomenon, for shearing rates larger than a given threshold. The disks' collective displacements in the shearing cell (back and ahead) is the counterpart of the constant velocity of the upper cover leading to a periodic behavior of the shear stress.