Granular media as rate-independent simple materials: Constitutive relations

1969 ◽  
Vol 3 (1) ◽  
pp. 344-351 ◽  
Author(s):  
G. Gudehus
Keyword(s):  
Granular Media ◽  
Constitutive Relations ◽  
Simple Materials

scholarly journals An anisotropic constitutive relation for the stress tensor of a rod-like (fibrous-type) granular material

2005 ◽  
Vol 2005 (6) ◽  
pp. 679-702 ◽  
Author(s):  
Mehrdad Massoudi
Keyword(s):  
Stress Tensor ◽  
Granular Media ◽  
Constitutive Relations ◽  
Transverse Isotropy ◽  
Yield Condition ◽  
Unit Vector ◽  
Constitutive Relationship ◽  
Fiber Direction ◽  
Stress Effects ◽  
Crystal Type

We will derive a constitutive relationship for the stress tensor of an anisotropic rod-like assembly of granular particles where not only the transverse isotropy (denoted by a unit vectorn, also called the fiber direction) is included, but also the dependence of the stress tensorTon the density gradient, a measure of particle distribution, is studied. The granular media is assumed to behave as a continuum, and the effects of the interstitial fluid are ignored. No thermodynamical considerations are included, and using representation theorems, it is shown that in certain limiting cases, constitutive relations similar to those of the Leslie-Ericksen liquid crystal type can be obtained. It is also shown that in this granular model, one can observe the normal stress effects as well as the yield condition, if proper structures are imposed on the material coefficients.

scholarly journals Experimental investigation and kinetic-theory-based model of a rapid granular shear flow

2008 ◽  
Vol 602 ◽  
pp. 63-79 ◽  
Author(s):  
R. D. WILDMAN ◽  
T. W. MARTIN ◽  
J. M. HUNTLEY ◽  
J. T. JENKINS ◽  
H. VISWANATHAN ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Shear Flow ◽  
Kinetic Theory ◽  
Granular Media ◽  
Constitutive Relations ◽  
Tracer Particle ◽  
Lower Boundary ◽  
Radioactive Tracer ◽  
Dissipative Systems ◽  
Wide Range

An experimental investigation of an idealized rapidly sheared granular flow was performed to test the predictions of a model based on the kinetic theory of dry granular media. Glass ballotini beads were placed in an annular shear cell and the lower boundary rotated to induce a shearing motion in the bed. A single particle was tracked using the positron emission particle tracking (PEPT) technique, a method that determines the location of a particle through the triangulation of gamma photons emitted by a radioactive tracer particle. The packing fraction and velocity fields within the three-dimensional flow were measured and compared to the predictions of a model developed using the conservation and balance equations applicable to dissipative systems, and solved incorporating constitutive relations derived from kinetic theory. The comparison showed that kinetic theory is able to capture the general features of a rapid shear flow reasonably well over a wide range of shear rates and confining pressures.

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.

Role of contact couples and couple stress in the behaviour of granular media

1998 ◽  
Vol 08 (PR8) ◽  
pp. Pr8-87-Pr8-94
Author(s):  
F. Dedecker ◽  
Ph. Dubujet ◽  
B. Cambou
Keyword(s):  
Couple Stress ◽  
Granular Media

Avalanche Stratification - Experimental Tests of the “Metastable Wedge” and “Continuous Flow” Models

2000 ◽  
Vol 627 ◽  
Author(s):  
M. E. Swanson ◽  
M. Landreman ◽  
J. Michel ◽  
J. Kakalios
Keyword(s):  
Continuous Flow ◽  
Granular Media ◽  
Experimental Tests ◽  
Coarse Sand ◽  
Angle Of Repose ◽  
Flow Models ◽  
Maximum Angle ◽  
Stratification Effect ◽  
Upward Moving ◽  
Moving Layer

ABSTRACTWhen an initially homogeneous binary mixture of granular media such as fine and coarse sand is poured near the closed edge of a “quasi-two-dimensional” Hele-Shaw cell consisting of two vertical transparent plates held a narrow distance apart, the mixture spontaneously forms alternating segregated layers. Experimental measurements of this stratification effect are reported in order to determine which model, one which suggests that segregation only occurs when the granular material contained within a metastable heap between the critical and maximum angle of repose avalanches down the free surface, or one for which the segregation results from smaller particles becoming trapped in the top surface and being removed from the moving layer during continuous flow. The result reported here indicate that the Metastable Wedge model provides a natural explanation for the initial mixed zone which precedes the formation of the layers, while the Continuous Flow model explains the observed upward moving kink of segregated material for higher granular flux rates, and that both mechansims are necessary in order to understand the observed pairing of segregated layersfor intermediate flow rates and cell separations.

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.

β-Cyclodextrin Polymers on Microcrystalline Cellulose as a Granular Media for Organic Micropollutant Removal from Water

2018 ◽  
Author(s):  
Diego Alzate-Sanchez ◽  
Yuhan Ling ◽  
Chenjun Li ◽  
Benjamin Frank ◽  
Reiner Bleher ◽  
...  
Keyword(s):  
Microcrystalline Cellulose ◽  
Continuous Flow ◽  
Granular Media ◽  
Anaerobic Biodegradation ◽  
Thin Coating ◽  
Micropollutant Removal ◽  
Cyclodextrin Polymers ◽  
Flow Experiments ◽  
Aerobic And Anaerobic ◽  
Cellulose Composite

This manuscript describes cyclodextrin polymers formed as a thin coating on microcrystalline cellulose. The resulting polymer/cellulose composite shows promising performance for removing organic pollutants from water and can be packed into columns for continuous-flow experiments. The polymer/cellulose composite also shows excellent resistance to aerobic and anaerobic biodegradation.

Perancangan Boneka Edukasi Terinspirasi oleh Pencipta Boneka Si Unyil

2018 ◽  
Vol 1 ◽  
Author(s):  
Azhari Amri
Keyword(s):  
Design Process ◽  
Urban Culture ◽  
Urban Life ◽  
Rural Region ◽  
The Public ◽  
The Creation ◽  
The Difference ◽  
The City ◽  
Simple Materials

Film Unyil puppet comes not just part of the entertainment world that can be enjoyed by people from the side of the story, music, and dialogue. However, there is more value in it which is a manifestation of the creator that can be absorbed into the charge for the benefit of educating the children of Indonesia to the public at large. The Unyil puppet created by the father of Drs. Suyadi is one of the works that are now widely known by the whole people of Indonesia. The process of creating a puppet Unyil done with simple materials and formation of character especially adapted to the realities of the existing rural region. Through this process, this research leads to the design process is fundamentally educational puppet inspired by the creation of Si Unyil puppet. The difference is the inspiring character created in this study is on the characters that exist in urban life, especially the city of Jakarta. Thus the results of this study are the pattern of how to shape the design of products through the creation of the puppet with the approach of urban culture.

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