Abstract
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.
Highlights
Granular materials are omnipresent in our daily life and widely used in various industries such as food, pharmaceutical, agriculture and mining
We have extended an existing rheological model that predicts the relation between volume fraction, Inertial number and Softness [52], including friction and cohesion dependencies
Two geometries are featured with two different cohesive contact models
Summary
Granular materials are omnipresent in our daily life and widely used in various industries such as food, pharmaceutical, agriculture and mining. When subjected to external shearing, granular systems exhibit a non-equilibrium jamming transition from a static solid-like to a dynamic, liquid-like state [6, 26] and to a steady state [57]. This particular transition drew much attention for dry and wet granular systems in both dilute and dense regimes [8, 14, 38, 39, 43, 46, 49, 58, 62, 65, 72, 73]. The influence of individual particle properties is better understood there is still very little known about the combined effect of particle friction and cohesion on the rheological behaviour of granular flows [48]
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