From Particles in Steady State Shear Bands via Micro-Macro to Macroscopic Rheology Laws

Luding, Stefan; Singh, Abhinendra; Roy, Sudeshna; Vescovi, Dalila; Weinhart, Thomas; Magnanimo, Vanessa

doi:10.1007/978-981-10-1926-5_2

Cited by 6 publications

(19 citation statements)

References 19 publications

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“…We compare our data for non-cohesive materials which is shown to be in agreement with the trend of data obtained from [40] for different external rotation rates. The black solid line corresponds to the data in the shear band center (˙ġ g > 0.8 max ) fitted by equation (14) with m = 0.16 o , m = ¥ 0.40 and I o =0.07 which are in close agreement with the fitting constants explained in [27]. Note that these fitting constants change with the range of I that are included in the fitting.…”

Section: Effect Of Inertial Numbersupporting

confidence: 75%

“…* p o denotes the limiting dimensionless pressure around the correction due to softness of the particles, where the correction is not applicable anymore, since  f 0 p for  * * p p o [27]. We have used this fit, as our data range is too limited to derive the functional form of the fit.…”

Section: Rheology Of Dry Granular Materials 41 Effect Of Softness Imentioning

confidence: 99%

“…For a full constitutive law, one also needs to take into account the solid volume fraction also. For dry granular shear flow [27,40], the constitutive relations for the volume fraction given by corrections (to first order) based on dimensionless numbers * p and I as follows:…”

Section: Rheological Modelmentioning

confidence: 99%

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A general(ized) local rheology for wet granular materials

2017

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We study the rheology of dry and wet granular materials in the steady quasistatic regime using the discrete element method in a split-bottom ring shear cell with focus on the macroscopic friction. The aim of our study is to understand the local rheology of bulk flow at various positions in the shear band, where the system is in critical state. We develop a general(ized) rheology, in which the macroscopic friction is factorized into a product of four functions, on top of the classical ( ) m I rheology, each of which depends on exactly one dimensionless control parameter, quantifying the relative importance of different micro-mechanical machanisms. These four control parameters relate the time scales of shear rateġ t , particle stiffness t k , gravity t g and cohesion t c , respectively, with the governing time scale of confining pressure t p . Whileġ t is large and thus of little importance for most of the slow flow data studied, it increases the friction in critical state, where the shear rate is high and decreases friction by relaxation (creep) where the shear rate is low. t g and t k are comparable to t p in the bulk, but become more or less dominant relative to t p at the extremes of low pressure at the free surface and high pressure deep inside the bulk, respectively. The effect of wet cohesion on the flow rheology is quantified by t c decreasing with increasing cohesion. Furthermore, the proposed rheological model predicts well the shear thinning behavior both in the bulk and near the free surface; shear thinning rate becomes less near the free surface with increasing cohesion.

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Section: Effect Of Inertial Numbersupporting

confidence: 75%

Section: Rheology Of Dry Granular Materials 41 Effect Of Softness Imentioning

confidence: 99%

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A general(ized) local rheology for wet granular materials

2017

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“…In order to complete the rheology for soft, compressible particles, a relation for the solid volume fraction (packing fraction) as function of pressure and shear rate is missing for dry non-cohesive materials. In [11], the following dependency was observed:…”

Section: Non-cohesive Granular Materialsmentioning

confidence: 92%

“…The typical strain rate for which dilation would turn to fluidization is I o = 0.85 , and the typical pressure level for which softness leads to huge densities is p o * = 0.33 [11]. Note that both correction functions are first order, i.e.…”

Section: Non-cohesive Granular Materialsmentioning

confidence: 99%

Effect of cohesion on local compaction and granulation of sheared soft granular materials

2017

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Abstract. This paper results from an ongoing investigation of the effect of cohesion on the compaction of sheared soft wet granular materials. We compare dry non-cohesive and wet moderately-to-strongly cohesive soft almost frictionless granular materials and report the effect of cohesion between the grains on the local volume fraction. We study this in a three dimensional, unconfined, slowly sheared split-bottom ring shear cell, where materials while sheared are subject to compression under the confining weight of the material above. Our results show that inter-particle cohesion has a considerable impact on the compaction of soft materials. Cohesion causes additional stresses, due to capillary forces between particles, leading to an increase in volume fraction due to higher compaction. This effect is not visible in a system of infinitely stiff particles. In addition, acting oppositely, we observe a general decrease in volume fraction due to increased cohesion for frictional particle, which we attribute to the role of contact friction that enhances dilation.

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Steady state rheology of homogeneous and inhomogeneous cohesive granular materials

et al. 2019

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This paper aims to understand the effect of different particle/contact properties like friction, softness and cohesion on the compression/dilation of sheared granular materials. We focus on the local volume fraction in steady state of various non-cohesive, dry cohesive and moderate to strong wet cohesive, frictionless-to-frictional soft granular materials. The results from (1) an inhomogeneous, slowly sheared split-bottom ring shear cell and (2) a homogeneous, stress-controlled simple shear box with periodic boundaries are compared. The steady state volume fractions agree between the two geometries for a wide range of particle properties. While increasing inter-particle friction systematically leads to decreasing volume fractions, the inter-particle cohesion causes two opposing effects. With increasing strength of cohesion, we report an enhancement of the effect of contact friction i.e. even smaller volume fraction. However, for soft granular materials, strong cohesion causes an increase in volume fraction due to significant attractive forces causing larger deformations, not visible for stiff particles. This behaviour is condensed into a particle friction—Bond number phase diagram, which can be used to predict non-monotonic relative sample dilation/compression.

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From Particles in Steady State Shear Bands via Micro-Macro to Macroscopic Rheology Laws

Cited by 6 publications

References 19 publications

A general(ized) local rheology for wet granular materials

A general(ized) local rheology for wet granular materials

Effect of cohesion on local compaction and granulation of sheared soft granular materials

Steady state rheology of homogeneous and inhomogeneous cohesive granular materials

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