Numerical studies of transportation of granular material by a pin-point blast using models of the mechanics of continuous and granular media

1998 ◽  
Vol 39 (1) ◽  
pp. 1-11
Author(s):  
V. V. Borovikov
Keyword(s):  
Granular Material ◽  
Granular Media ◽  
Numerical Studies

Stress fields in granular material and implications for performance of robot locomotion over granular media

2015 ◽  
Vol 8 (1) ◽  
pp. 2005-2009
Author(s):  
Diandong Ren ◽  
Lance M. Leslie ◽  
Congbin Fu
Keyword(s):  
Mechanical Properties ◽  
Granular Material ◽  
Granular Media ◽  
Rotation Frequency ◽  
Legged Locomotion ◽  
Working Environment ◽  
Navier Stokes ◽  
Maximum Speed ◽  
Sigmoid Curve ◽  
Multi Body

 Legged locomotion of robots has advantages in reducing payload in contexts such as travel over deserts or in planet surfaces. A recent study (Li et al. 2013) partially addresses this issue by examining legged locomotion over granular media (GM). However, they miss one extremely significant fact. When the robot’s wheels (legs) run over GM, the granules are set into motion. Hence, unlike the study of Li et al. (2013), the viscosity of the GM must be included to simulate the kinematic energy loss in striking and passing through the GM. Here the locomotion in their experiments is re-examined using an advanced Navier-Stokes framework with a parameterized granular viscosity. It is found that the performance efficiency of a robot, measured by the maximum speed attainable, follows a six-parameter sigmoid curve when plotted against rotating frequency. A correct scaling for the turning point of the sigmoid curve involves the footprint size, rotation frequency and weight of the robot. Our proposed granular response to a load, or the ‘influencing domain’ concept points out that there is no hydrostatic balance within granular material. The balance is a synergic action of multi-body solids. A solid (of whatever density) may stay in equilibrium at an arbitrary depth inside the GM. It is shown that there exists only a minimum set-in depth and there is no maximum or optimal depth. The set-in depth of a moving robot is a combination of its weight, footprint, thrusting/stroking frequency, surface property of the legs against GM with which it has direct contact, and internal mechanical properties of the GM. If the vehicle’s working environment is known, the wheel-granular interaction and the granular mechanical properties can be grouped together. The unitless combination of the other three can form invariants to scale the performance of various designs of wheels/legs. Wider wheel/leg widths increase the maximum achievable speed if all other parameters are unchanged.

A New Simple Non Linear Modelling of the Quasi Statics of Granular Media: predictions, comparisons with experiments

2000 ◽  
Vol 627 ◽  
Author(s):  
Pierre Evesque
Keyword(s):  
Granular Material ◽  
Granular Media ◽  
Stress Ratio ◽  
Rheological Behaviour ◽  
Stress Strain ◽  
Linear Modelling ◽  
Non Linear ◽  
Strain Paths ◽  
Contact Distribution

ABSTRACTFirst, a non linear incremental modelling is proposed to describe rheological behaviour of granular material under different simple (i.e. triaxial-, oedometric-, undrained-) stress-strain paths. Validity of isotropic-response assumption is demonstrated whatever the stress ratio as far as deformation range remains small (ε1<5%). This contradicts some recent hypothesis made on the evolution of contact distribution during anisotropic loading.

COMPACTION AND DENSITY FLUCTUATIONS IN VIBRATED GRANULAR MEDIA

2001 ◽  
Vol 04 (04) ◽  
pp. 389-396
Author(s):  
A. C. B. BARNUM ◽  
ARIF OZBAY ◽  
E. R. NOWAK
Keyword(s):  
Steady State ◽  
Granular Material ◽  
Time Scale ◽  
Granular Media ◽  
Cylindrical Tube ◽  
Density Fluctuations ◽  
Noise Power ◽  
Third Order ◽  
State Densities ◽  
Irreversible Relaxation

We report measurements of the density of a vibrated granular material as a function of time or taps. The material studied consists of monodisperse spherical glass beads confined to a long, thin cylindrical tube. Changes in vibration intensity are used to induce transitions between two steady state densities that depend on the intensity of the vibrations. We find a complex time evolution similar to previous work on the irreversible relaxation from a loose state toward a steady state. In addition, frequency dependent third order moments of the density fluctuations are measured. The data indicate a coupling between large variations in density on one time scale and noise power over a broad range of higher-frequency scales.

scholarly journals Granular Media Friction Pad for Robot Shoes—Hexagon Patterning Enhances Friction on Wet Surfaces

2021 ◽  
Vol 11 (23) ◽  
pp. 11287
Author(s):  
Halvor T. Tramsen ◽  
Lars Heepe ◽  
Stanislav N. Gorb
Keyword(s):  
Internal Friction ◽  
Granular Material ◽  
Contact Area ◽  
Granular Media ◽  
Elastic Membrane ◽  
Mechanical Interlocking ◽  
Material Flows ◽  
Friction Forces ◽  
Jamming Transition ◽  
Universal Applicability

For maximizing friction forces of the robotic legs on an unknown/unpredictable substrate, we introduced the granular media friction pad, consisting of a thin elastic membrane encasing loosely filled granular material. On coming into contact with a substrate, the fluid-like granular material flows around the substrate asperities and achieves large contact areas with the substrate. Upon applying load, the granular material undergoes the jamming transition, rigidifies and becomes solid-like. High friction forces are generated by mechanical interlocking on rough substrates, internal friction of the granular media and by the enhanced contact area caused by the deformation of the membrane. This system can adapt to a large variety of dry substrate topologies. To further increase its performance on moist or wet substrates, we adapted the granular media friction pad by structuring the outside of the membrane with a 3D hexagonal pattern. This results in a significant increase in friction under lubricated conditions, thus greatly increasing the universal applicability of the granular media friction pad for a multitude of environments.

GRAIN NON-SPHERICITY EFFECTS ON THE ANGLE OF REPOSE OF GRANULAR MATERIAL

1993 ◽  
Vol 07 (09n10) ◽  
pp. 2037-2046 ◽  
Author(s):  
JASON A.C. GALLAS ◽  
STEFAN SOKOLOWSKI
Keyword(s):  
Granular Material ◽  
Granular Media ◽  
Angle Of Repose ◽  
Site Model ◽  
Specific Effects ◽  
A Site ◽  
Spherical Grains

We use a site-site model to describe non-sphericity of particles composing a granular media. Specific effects of grain non-sphericity 011 the angle of repose are investigated. We report evidence indicating the possible existence of a shape-roughness threshold for grains: below it angles of repose are essentially the same as those obtained for spherical grains; above it there are pronounced changes 011 the angle of repose and it is possible to find rather large piles of grains.

scholarly journals Liquid clustering and capillary pressure in granular media

2014 ◽  
Vol 762 ◽  
Author(s):  
Jean-Yves Delenne ◽  
Vincent Richefeu ◽  
Farhang Radjai
Keyword(s):  
Granular Material ◽  
Granular Media ◽  
Capillary Condensation ◽  
Peak Stress ◽  
Secondary Process ◽  
Coalescence Process ◽  
Liquid Distribution ◽  
Lattice Boltzmann Simulations ◽  
Liquid Clusters ◽  
Condensed Liquid

AbstractBy means of extensive lattice Boltzmann simulations, we investigate the process of growth and coalescence of liquid clusters in a granular material as the amount of liquid increases. A homogeneous grain–liquid mixture is obtained by means of capillary condensation, thus providing meaningful statistics on the liquid distribution inside the granular material. The tensile stress carried by the grains as a function of the amount of condensed liquid reveals four distinct states, with a peak stress occurring at the transition from a primary coalescence process, where the cohesive strength is carried mostly by the grains, to a secondary process governed by the increase of the liquid cluster volumes. We show that the evolution of capillary states is correctly captured by a simple model accounting for the competing effects of the Laplace pressure and grain–liquid interface.

The dynamics of multiparticle collisions in motion of a granular material

Open Physics ◽  
2003 ◽  
Vol 1 (4) ◽  
Author(s):  
Jacek Leszczyński
Keyword(s):  
Molecular Dynamics ◽  
Fractional Calculus ◽  
Granular Material ◽  
Granular Media ◽  
Complex Problem ◽  
Repulsive Force ◽  
Direct Influence ◽  
Dissipation Of Energy ◽  
Dynamics Method ◽  
Cohesive Materials

AbstractWe consider the complex problem of how to calculate particle motions taking into account multiparticle collisions. Multiparticle contacts occur when a particle collides with neighbouring particles, so that those contacts have a direct influence on each other. We will focus on the molecular dynamics method. Particularly, we will analyse what happens in cohesive materials during multiparticle contacts. We investigated the expression of repulsive force formulated under fractional calculus which is able to control dynamically the transfer and dissipation of energy in granular media. Such approach allows to perform simulations of arbitrary multiparticle collisions and also granular cohesion dynamics.

What Is Shaking in the Sandbox?

MRS Bulletin ◽  
1994 ◽  
Vol 19 (5) ◽  
pp. 25-31 ◽  
Author(s):  
Heinrich M. Jaeger ◽  
James B. Knight ◽  
Chu-heng Liu ◽  
Sidney R. Nagel
Keyword(s):  
Granular Material ◽  
Granular Media ◽  
Granular Matter ◽  
Practical Importance ◽  
Granular Dynamics ◽  
Recent Developments ◽  
The Common ◽  
Convection Rolls ◽  
Sand And Gravel

In 1831, Faraday reported to the Royal Society of London that granular material inside a container, when vibrated, would spontaneously begin to exhibit convection rolls, similar to what is observed in normal fluids when heated from below. This observation indicated that not only can a granular material act like a fluid, but also that vibrations can affect the properties of these materials in important ways. Such phenomena are of immediate practical importance because granular materials exist all around us. We use sand and gravel to build the roads we drive on; we process grain to provide our food supply; we mine ore to provide coal, minerals, and precious commodities; we take powders and pills to cure what ails us. Many of the phenomena observed in granular media are prototypical examples of complex, nonequilibrium behavior that is also found in an increasing number of other systems. As a result, sandpiles have served as a macroscopic and visually appealing metaphor for thinking about a number of microscopic systems that are not directly accessible to our senses. Despite the common occurrence of these materials, their properties are not at all well understood and most of our knowledge centers on the subset of static, equilibrium properties of granular matter. Only over the last few years have physicists and engineers begun to unravel some of the exceptional time-dependent, nonequilibrium properties that these seemingly simple materials exhibit. This review focuses on recent developments in the newly emerging field of granular dynamics and, in particular, addresses the role of vibration in determining the phenomena observed in such media.

scholarly journals Flows of cohesive granular media

2021 ◽  
Vol 249 ◽  
pp. 01001
Author(s):  
Sandip Mandal ◽  
Adrien Gans ◽  
Maxime Nicolas ◽  
Olivier Pouliquen
Keyword(s):  
Granular Media ◽  
Flow Behavior ◽  
Constitutive Relations ◽  
Shear Banding ◽  
Plane Shear ◽  
Simple Method ◽  
Plastic Properties ◽  
Shear Cell ◽  
Numerical Studies ◽  
Long Time

Cohesive granular media have broad applications in industries. However, our understanding of their flow behavior is still limited compared to dry granular media, although rich knowledge about their static and plastic properties has been gained. In this paper, we provide some insights into the flow behavior of cohesive granular media from our recent numerical studies using an inclined plane and a plane shear cell. We evidence that the cohesive nature of flows is significantly affected by material properties of the particles like stiffness and inelasticity in addition to the inter-particle adhesion and introduce the concept of “effective” adhesion, which incorporates the effects of these three variables. We propose constitutive relations involving dimensionless inertial number and “effective” cohesion number, based on the “effective” adhesion to describe the rheology. We also show that increasing adhesion increases the hysteresis in granular media, evidencing the existence of a prominent shear weakening branch in the friction coefficient versus inertial number rheological curve. Moreover, we reveal that this increasing hysteresis gives rise to the increasing occurrence of shear banding instability, pointing to the increasing possibility of jamming in cohesive granular media. Finally, we present a promising experimental approach to investigate the flow behavior of cohesive granular materials, based on a simple method of preparing a long time stable medium with a controlled adhesion between particles.

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