Effect of vibration on flow properties of fine glass beads

Abstract

in Wiley InterScience (www.interscience.wiley.com).An estimation of cohesion C and angle of internal friction u of fine glass beads, which have been previously subjected to small intensity vertical vibrations of controlled frequency and amplitude for a fixed period of time, is presented. In the range of vibration intensities tested previbration causes powder compaction. Experimental measurements to obtain C and u have been performed by means of a centrifuge powder tester in which the previbrated powder bed is rotated around its vertical axis. At a critical rotation velocity the shear stress induced by rotation is large enough to drive material avalanches. From a theoretical analysis of these avalanches, based on the Coulomb's method of wedges, C and u are derived. We have found a significant increase of cohesion, and a slight decrease of the angle of internal friction as the effective consolidation stress due to previbration is increased. The estimated interparticle cohesion force f t from the experimental measurements, and using a Rumpf's averaging equation, is in agreement with the calculated interparticle attractive force due to van der Waals and capillary interaction for the unconsolidated beds. Moreover f t increases as the effective consolidation stress is increased in agreement with estimations from theoretical models based on contact plasticity. This result suggests that, at the microscopic level of asperities, compaction due to previbration is able to induce plastic deformation of the contacts.

Measurement of surface deformation and cohesion of a granular pile under the effect of centrifugal force

“…In fact, centrifugal methods have been widely used for a number of granular-related experiments. Examples include the centrifuge-based dehydration [15], dredge pumping [16], soil characterization [17], silo discharging [18], surface deformation [19], cohesion measurement [20,21], and mechanical characterization [22][23][24]. In general, centrifuge is useful to separate, transport and deform various materials.…”

“…Particularly, difference between cohesive and non-cohesive grains is analyzed on the basis of experimental results. The developed system is similar to the apparatus reported in [22,23]. In these studies, flowability has been evaluated using a rotating two-dimensional granular layer.…”

“…Thus, we build a new experimental setup to reveal the mechanics of granular pile relaxation due to the competition between the centrifuge and gravity. In addition to the original setup, the new instrument developed in this study achieves rapid rotation (over 800 rpm) compared with the previous instrument (550 rpm) [22,23].…”

Mechanical Strength of Humidified Glass Beads

“…8, the angle of avalanche should be very close to the angle of internal friction (a ~ 0), which is seen not to depend essentially on bead size in the range of sizes tested. Indeed, the values measured are around 260, which is about the angle of internal friction measured for fine glass beads using a Ring Shear Tester and a Centrifuge Tester (see [8] for additional details on this measurements). In contrast, it is observed in Fig.…”

History-dependent deformation of a rotated granular pile governed by granular friction

“…Recently, we developed a new apparatus by which the deformation of a quasi-two-dimensional (2D) granular pile can be precisely measured [39,40]. This type of rotating 2D setup is useful to characterize mechanical properties of granular matter [41,42,43].…”