Shear Banding

The shear strain is not distributed uniformly through the sample. In the movie above, each grain is colored in proportion to its upward displacement with blue least and red the full height of the box. Grains in the left half have not moved at all and in the right half, the grain displacement rises rapidly as one approaches the wall.

The average vertical displacement is depicted at 25%, 50% and 75% shear in the figure below. Small oscillations in the curves are due to grain rotations. The straight lines indicate uniform deformation. Motion of the grains is concentrated near the moving boundary on the right. The shear band involves approximately 1/3 of the domain, or is 7 mean particle diameters wide.