Behavior of granular materials under cyclic shear.

Area of Science:

• Physics
• Materials Science
• Rheology

Background:

• Granular materials exhibit complex flow behaviors under shear.
• Traditional Couette geometries introduce curvature effects, limiting parallel shear studies.
• Understanding shear flow is crucial for predicting granular material behavior in various applications.

Purpose of the Study:

• To design and develop a novel parallel plate shear cell for granular materials.
• To investigate transient shear flow and shear-induced crystallization.
• To accurately measure velocity profiles during shear.

Main Methods:

• Development of a parallel plate shear cell with independently movable slats.
• Utilizing deformable side walls to accommodate grain motion.
• Direct measurement of granular velocity profiles across the shear cell.

Main Results:

• Initial shear profiles vary significantly with packing.
• Shear flow sharpens the velocity profile, transitioning from linear to exponential decay.
• Further shearing leads to Gaussian or error function profiles, indicating complex dynamics.
• Cyclic shear induces large-scale ordering, affecting slip and lock-up phenomena.

Conclusions:

• The parallel plate shear cell effectively studies granular shear flow without curvature.
• Shear-induced crystallization and ordering are significant phenomena in granular dynamics.
• The cell provides insights into transitional and steady-state flow regimes in granular materials.