Figure 2. Video capture of the shearing glass beads

2.3 Data analysis of shear test results

The key outputs from ring shear measurements analyzed for each binary blend include pre-shear stress (τpre), unconfined yield strength (σu), flow function coefficient (FFc), packing density, and linearized friction angle (φ). The pre-shear stress, τpre, is the first point of measurement on the material, and represents the shear stress required to achieve steady state flow at a specified pre-shear load, σpre. In this work, σpre was fixed at 2000 Pa for all systems evaluated. The unconfined yield strength, σu, is the stress required to fail the material in an unconfined state after subjected to major principal stress. This parameter gives an indication of the overall strength of the powder. A physical representation of these parameters are in Figure 3.