An Experimental Study of the Rapid Flow of Dry Cohesionless Metal Powders

Abstract

This paper studies the rapid shearing flow of dry metal powders. To perform this study, we built and used an annular shear cell test apparatus. In this apparatus the dry metal powders are rapidly sheared by rotating one of the shear surfaces while the other shear surface remains fixed. The shear stress and normal stress on the stationary surface were measured as a function of three parameters: the shear-cell gap thickness, the shear-rate and the fractional solids content. Stresses are measured while holding both the fractional-solids content and the gap thickness at prescribed values. The results show the dependence of the normal stress and the shear stress on the shear-rate. Likewise, a significant stress dependence on both the fractional solids content and the shear-cell gap thickness was observed. Our experimental results are compared with the results of other reported experimental studies.

Rheophysics of dense granular materials: Discrete simulation of plane shear flows

“…It is noteworthy that a small variation of solid fraction (of the order of 10%) is enough to induce a variation of effective friction by a factor 4 ! This decrease of the effective friction when the solid fraction increases is contrary to the observation in static compaction [80], but was previously observed under shear [65].…”

Transport property measurements in sheared granular flows

“…(7) was first found from Bagnold's (1954) experiment which was performed in a Couette shear cell with wax spheres suspended in a glycerine-water-alcohol mixture. The result was also confirmed by several experimental studies of dry granular flows (Craig et al, 1986;Savage and Mckeown, 1983;Savage and Sayed, 1984;Hanes and Inman, 1985). Many simulations also demonstrated the above relation (Campbell and Brennen, 1985;Campbell and Gong, 1986;Hopkins and Shen, 1992;Walton and Braun, 1986;Campbell, 1989).…”

Mechanics of Granular Flows

“…But, at low concentrations, the collisional stresses are negligible compared to the kinetic or transport terms resulting from the transport of momentum by particle translation across shear layers. The predicted stress levels (at high concentrations) are in the same range as the stresses measured in annular shear cell experiments (Savage & Sayed 1984, Hanes & Inman 1985, Craig, et al 1986). …”

“…A number of experiments have been performed using annular shear cells to obtain information about the dependence of shear and normal stresses upon shear-rate and particle Hanes & Inman 1985, Craig, et al 1986, Stadler & Buggisch 1985, Stadler 1986). Most experimental arrangements are similar to that of Savage & Sayed 1984 (figure 8) which was the first shear cell designed to obtain granular flow rheological data at high shear-rates.…”