Anisotropy in particle contacts associated with shearing in granular media

Arthur, J. R. F.; Koenders, M. A.; Wong, R. K. S.

doi:10.1007/bf01180095

Cited by 20 publications

(19 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We find that, as is the case for other anisotropies in granular flow [62,63,64,65,66,67], the functional form of ξ(θ) is well characterized by the first two terms in the Fourier series…”

Section: Anisotropy In the Angular Dependence Of ξsupporting

confidence: 54%

Spatial force correlations in granular shear flow. I. Numerical evidence

2007

View full text Add to dashboard Cite

We investigate the emergence of long-range correlations in granular shear flow. By increasing the density of a simulated granular flow we observe a spontaneous transition from a dilute regime, where interactions are dominated by binary collisions, to a dense regime characterized by large force networks and collective motions. With increasing density, interacting grains tend to form networks of simultaneous contacts due to the dissipative nature of collisions. We quantify the size of these networks by measuring correlations between grain forces and find that there are dramatic changes in the statistics of contact forces as the size of the networks increases. Interactions in realistic granular materials arise due to grain elasticity and friction, but are complicated by various other mechanisms including humidity [5,6,7,8,9], grain shapes [10,11,12], and fracture processes occurring within the material [13]. However, a great deal of theoretical and computational progress has been made using the simple approximation that grains are spherical and perfectly dry [14]. In this case a purely repulsive force arises when two grains come into contact due to the deformation of grains and friction between grains.Understanding the nature of grain forces and dynamics, even in this relatively simple case, has proven difficult. At very low densities it can safely be assumed that only binary interactions occur and constitutive relations can be determined by statistically tracking the repulsive force created in each interaction. This is the basis of kinetic theory, which has been successfully applied to granular flows [15,16]. However, for very large densities, it is observed that multi-grain contacts always occur [17,18,19] and contact forces are transmitted through "force chain networks" formed by the topology of the contact network [14,21,22,23]. For these high densities the forces between contacting grains still arise from grain deformation and friction, but the extent of the interactions is not localized and depends on properties of the force chain networks.The presence of force chain networks calls into question theories that assume localized interactions and has inspired new models based on properties of the force chains [24,25,26,27,28,29,30]. However, although force networks can be visualized, it has proven difficult to measure quantitative correlations between contact forces [31,32,33,34]. This has led to the speculation that force chain networks are simply a perceived correlation, until recently when long-range correlations were measured between the averaged contact forces in a quasi-static

show abstract

“…We find that, as is the case for other anisotropies in granular flow [62,63,64,65,66,67], the functional form of ξ(θ) is well characterized by the first two terms in the Fourier series…”

Section: Anisotropy In the Angular Dependence Of ξsupporting

confidence: 54%

Spatial force correlations in granular shear flow. I. Numerical evidence

2007

View full text Add to dashboard Cite

show abstract

“…These functions are π-periodic and can be written as Fourier Series, keeping only terms that are also π-periodic. Previous research on the contact probability [40,41,42,43,44] has shown that C(θ) is well approximated by keeping only the lowest Fourier terms. We find that F bc (θ) has the same property.…”

Section: C(θ)mentioning

confidence: 99%

“…gives the probability to have a single contact at angle θ [40,41,42,43,44]. In the case that there are two (or more) contacts on a single grain, which is necessary to form a chain, this probability must be modified [45].…”

Section: C(θ)mentioning

confidence: 99%

Spatial force correlations in granular shear flow. II. Theoretical implications

2007

View full text Add to dashboard Cite

Numerical simulations are used to test the kinetic theory constitutive relations of inertial granular shear flow. These predictions are shown to be accurate in the dilute regime, where only binary collisions are relevant, but underestimate the measured value in the dense regime, where force networks of size ξ are present. The discrepancy in the dense regime is due to non-collisional forces that we measure directly in our simulations and arise from elastic deformations of the force networks. We model the non-collisional stress by summing over all paths that elastic waves travel through force networks. This results in an analytical theory that successfully predicts the stress tensor over the entire inertial regime without any adjustable parameters.

show abstract

“…The second pseudo-yield surface is used to reflect sand fabric anisotropy, including initial and stress-induced anisotropy. It was discovered that the stressinduced anisotropic fabric can be best represented with the plastic deviatoric strain [5,18]. Arthur et al's [5] tests involved a change in major principal stress direction for reloading following the initial loading and unloading to zero deviatoric stress.…”

Section: Pseudo-yield Surfacesmentioning

confidence: 99%

“…A significant portion of stress-induced anisotropy remains even after unloading. It has been observed [4,5] that, although initially there were very little differences, shearing along different directions following a loading-unloading cycle gives different responses in terms of hardening and volumetric change. The yield surface for medium-dense and dense sands is almost linear in p-q space [6].…”

Section: Introductionmentioning

confidence: 95%

A middle surface concept (MSC) model for saturated sands in general stress space

Yang

Muraleetharan

2006

Int. J. Numer. Anal. Meth. Geomech.

View full text Add to dashboard Cite

SUMMARYAn elastoplastic constitutive model is proposed for saturated sands in general stress space using the middle surface concept (MSC). In MSC, different features of stress-strain response of a material are divided into different pseudo-yield surfaces. The true-yield surface representing the true response is established by using various links between the yield surfaces. In this MSC sand model, several well-known features of sand response are represented by three different pseudo-yield surfaces, which are developed in a simple and straightforward way. These features include the critical state behaviour, the effects of state parameter, unloading and reloading plastic deformation, the influence of fabric anisotropy, and phase transformation line related behaviour. Finally, the model predictions and test results are compared for two different types of sands under a variety of loading conditions and good comparisons are obtained. The application of MSC to saturated sand modelling shows the versatility of MSC as a general concept for modelling stress-strain response of materials.

show abstract

Anisotropy in particle contacts associated with shearing in granular media

Cited by 20 publications

References 8 publications

Spatial force correlations in granular shear flow. I. Numerical evidence

Spatial force correlations in granular shear flow. I. Numerical evidence

Spatial force correlations in granular shear flow. II. Theoretical implications

A middle surface concept (MSC) model for saturated sands in general stress space

Contact Info

Product

Resources

About