Improvements in Powder Rheometry Through Novel 3D Printed Tools

Abstract

Powders and other granular media are used in a variety of industries, including pharmaceutical manufacturing, 3D printing, food production, construction, and more. As such, understanding the frictional rheological behavior of granular media is of great interest. We present a novel testing paradigm to characterize the rheology of granular media in both the quasistatic and transitional regimes. We introduce a family of 3D printed tools. The main geometry comprises an annular helix formed to smoothly penetrate a powder bed and measure while compressing powder due to the helix shape. To optimize the design, we varied the helix angle from 10° to 35° and blade count from 2 to 6 and tested this range of designs experimentally. In addition, we introduce an aerated cup to optionally aerate and fluidize the powder bed during measurements. Using this method, we report the frictional rheology flow curve of noncohesive glass microspheres for shear rates ranging from 0.53s⁻¹ to 5300s⁻¹, or inertial number I ranging from 6.9×10⁻⁵ to 0.95. We also demonstrate that this form of tool is robust against perturbations from aeration, and that data still collapse to the same measurements for multiple aerated conditions.