Computational Examination of Stress Relaxation and Shear Banding in Sheared Amorphous Materials

Shear banding occurs in a variety of amorphous materials when yielding under shear deformation, from food and cosmetic products to cements and soils, where only parts of the material flow while others remain "stuck". While this phenomenon is broadly observed, its microscopic origins and its link to yielding transitions are not well understood. Using data from large-scale 3D computer simulations [1,2], which model non-Brownian jammed suspensions of soft, spherical particles, we examine the influence of the deformation rate and sample age on the relaxation of stresses and the onset of banded flow. Load curves are analyzed to characterize the severity of the stress drops, while profiles of the particle velocities are used to examine the development of shear bands. Theoretical models [3] have recently demonstrated the dependence of the severity of the stress drop and the development of shear bands in these systems on the history of the material and the shear rate. Through our computational analysis, we demonstrate an increase in the severity of the stress drop and the degree of banding as shear rate decreases and sample age increases, which agree with theoretical predictions. At high rates, these materials begin to yield and flow in a uniform, ductile fashion, while at low rates we see a sudden, severe drop in shear stress, or brittle yielding, which leads to the development of strong, and persistent, shear banding.