Flow behavior of cohesive and frictional fine powders

Luding, Stefan; Tykhoniuk, R.; Tomas, Jürgen; Heim, Lars; Kappl, Michael; Butt, Hans‐Jürgen

doi:10.1201/b17007-25

Cited by 1 publication

(2 citation statements)

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“…In this region the average volume remains constant. The PFC-results agree qualitatively with the ones obtained with molecular dynamics simulations by Luding [20,21,22].…”

Section: Resultssupporting

confidence: 84%

“…We evaluated the velocities of the grains for the CDsimulations and found shear localization in shear bands. In contrast to previous simulations [20,21,22], where the left wall was fixed, i.e. strain controlled, whereas the right one was stress controlled, the shear band which forms initially, is oriented along either diagonal, breaking the symmetry of our system spontaneously.…”

Section: Resultscontrasting

confidence: 66%

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Influence of particle elasticity in shear testers

et al. 2005

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Two dimensional simulations of non-cohesive granular matter in a biaxial shear tester are discussed. The effect of particle elasticity on the mechanical behavior is investigated using two complementary distinct element methods (DEM): Soft particle molecular dynamics simulations (Particle Flow Code, PFC) for elastic particles and contact dynamics simulations (CD) for the limit of perfectly rigid particles. As soon as the system dilates to form shear bands, it relaxes the elastic strains so that one finds the same stresses for rigid respectively elastic particles in steady state flow. The principal stresses in steady state flow are determined. They are proportional to each other, giving rise to an effective macroscopic friction coefficient which is about 10 % smaller than the microscopic friction coefficient between the grains. Correspondence to: kadau@comphys.uni-duisburg.de der to calculate dense granular flows. These models contain parameters whose connection to the properties of the grains is not yet understood. It is the aim of distinct element simulation methods (DEM) to establish the connection between the grain scale and the macroscopic behavior directly [2,3].The stress-strain behavior of a dense granular assembly consists of two parts: the rearrangement of the particles on the one hand, and their individual elastic or plastic deformation on the other. In this paper we address the question, how strongly the flow properties are influenced by the grain deformations compared to particle rearrangements. Therefore, two different distinct element methods are used: soft particle molecular dynamics modelling elastic particles (used here: PFC) and contact dynamics (CD) to simulate perfectly rigid particles. By comparing the results of the two methods the influence of particle elasticity can be separated from the effect that particle rearrangements have on the macroscopic stress-strain behavior found in e.g. the biaxial shear tester considered here.We simulate dense granular flow in a biaxial tester, which allows for larger displacements than the Jenike shear cell. The biaxial shear tester is a rectangular box [4,5] in which the material is sheared under constant strain rate in one direction and constant stress in a perpendicular direction while the load plates in the third direction are fixed. In this setup one will reach steady state flow (constant volume and stress tensor), and the yield locus can be determined.2 Models Both models we use simulate the trajectory of each individual particle by integrating Newton's equations. They mainly differ in the way, how the contact forces between grains are determined. In soft particle molecular dynamics (PFC) microscopic elastic deformations of each particle have to be taken into account: They determine the forces. By contrast, in contact dynamics (CD) particles are considered as perfectly rigid, and forces are calculated from the volume exclusion constraint.In order to make the comparison between the two methods as stringent as possible, we simulate a very simple...

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“…In this region the average volume remains constant. The PFC-results agree qualitatively with the ones obtained with molecular dynamics simulations by Luding [20,21,22].…”

Section: Resultssupporting

confidence: 84%

Section: Resultscontrasting

confidence: 66%