Product Design of Cohesive Powders – Mechanical Properties, Compression and Flow Behavior

Tomas, Jürgen

doi:10.1002/ceat.200406134

Cited by 63 publications

(17 citation statements)

References 70 publications

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“…Interesting granular phenomena like yielding and jamming (Liu and Nagel, 1998;Bi et al, 2011;Luding, 2016;Kumar and Luding, 2016), dilatancy (Cates et al, 2005;Van Hecke, 2009;Yang et al, 2015), shear-band localization (Alshibi and Sture, 2000;Singh et al, 2014), history-dependence (Thakur et al, 2014), and anisotropy (Radjai et al, 1996;Majmudar and Behringer, 2005) have attracted significant scientific interest over the past decades (Savage and Hutter, 1989;Cundall, 1989;Radjai et al, 1999;Wolf et al, 2000;† GDR-MiDi, 2004;Tomas, 2005;Alonso-Marroquin and Herrmann, 2004;Luding 2005aLuding , b, 2008. Various laboratory element tests can be performed to study the bulk behaviour of granular materials (Schwedes, 2003).…”

Section: Introductionmentioning

confidence: 99%

Effect of Particle Size and Cohesion on Powder Yielding and Flow

Shi

Mohanty

Chakravarty

et al. 2018

KONA

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The bulk properties of powders depend on material characteristics and size of the primary particles. During storage and transportation processes in the powder processing industry, the material undergoes various modes of deformation and stress conditions, e.g., due to compression or shear. In many applications, it is important to know when powders are yielding, i.e. when they start to flow under shear; in other cases it is necessary to know how much stress is needed to keep them flowing. The measurement of powder yield and flow properties is still a challenge and will be addressed in this study. In the framework of the collaborative project T-MAPPP, a large set of shear experiments using different shear devices, namely the Jenike shear tester, the ELE direct shear tester, the Schulze ring shear tester and the FT4 powder rheometer, have been carried out on eight chemically-identical limestone powders of different particle sizes in a wide range of confining stresses. These experiments serve two goals: i) to test the reproducibility/ consistency among different shear devices and testing protocols; ii) to relate the bulk behaviour to microscopic particle properties, focusing on the effect of particle size and thus inter-particle cohesion. The experiments show high repeatability for all shear devices, though some of them show more fluctuations than others. All devices provide consistent results, where the FT4 powder rheometer gives lower yield/steady state stress values, due to a different pre-shearing protocol. As expected, the bulk cohesion decreases with increasing particle size (up to 150 μm), due to the decrease of inter-particle cohesion. The bulk friction, characterized in different ways, is following a similar decreasing trend, whereas the bulk density increases with particle size in this range. Interestingly, for samples with particle sizes larger than 150 μm, the bulk cohesion increases slightly, while the bulk friction increases considerably-presumably due to particle interlocking effects-up to magnitudes comparable to those of the finest powders. Furthermore, removing the fines from the coarse powder samples reduces the bulk cohesion and bulk density, but has a negligible effect on the bulk friction. In addition to providing useful insights into the role of microscopically attractive, van der Waals, gravitational and/or compressive forces for the macroscopic bulk powder flow behaviour, the experimental data provide a robust database of cohesive and frictional fine powders for industrially relevant designs such as silos, as well as for calibration and validation of models and computer simulations.

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Section: Introductionmentioning

confidence: 99%

Effect of Particle Size and Cohesion on Powder Yielding and Flow

Shi

Mohanty

Chakravarty

et al. 2018

KONA

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“…Tomas [32,33] considered an elastic-plastic particle contact model in order to describe the failure/flowability conditions of a bulk powder. He proposed the following equation for the quantification of the IPFs:…”

Section: Theoretical Frameworkmentioning

confidence: 99%

“…In order to relate the microscopic interparticle interactions to bulk flow properties, the model proposed by Tomas [32,33] for steady-state flow criterion of particles can be followed.…”

Section: Theoretical Frameworkmentioning

confidence: 99%

“…Furthermore, in this paper, in place of the purely plastic deformation model suggested by Molerus [29], a novel procedure to correlate microscopic interparticle forces to the measured macroscopic bulk flow properties is proposed. This is based on the theoretical modelling approach proposed by Tomas [32,33] that was developed to account for elastic-plastic particle deformation at the contact points.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of industrial reactive powders flow properties at high temperature

et al. 2017

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“…At the onset of circulation, a failure plane would be created in the bed as force chains buckled and ruptured between the layer of the particles at the drum and those directly above. Upon forming this shear plane, dilatancy of the bed resulted 44 whereby particle rearrangement, contact unloading, and volume expansion ensued. Momentum transfer from the moving particles at the drum to the adjacent layers through collisions and cohesive interparticle interactions created the circulating patterns observed.…”

Section: Discussionmentioning

confidence: 98%

Cohesive‐driven particle circulation in the solids conveying zone of a single‐screw extruder

2008

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ABSTRACT:Aspects of heat transfer within the solids conveying zone of a single-screw extruder were studied by using a specially constructed drum testing apparatus. Experiments were conducted with linear low-density polyethylene, polystyrene (PS), and polypropylene (PP) samples by examining their transient temperature profile while the heated drum was stationary or moving. In accordance with classic solids conveying theory, the granular beds of PP and PS remained as plugs while the drum rotated. In such cases, the dominant modes of heat transfer for these systems are conduction through the contact area of a particle and conduction through the interstitial gas. An exception to this behavior was found with PE, in which the bed temperature increased more rapidly while the drum rotated. Visual observations of the bed showed that the particles circulated in the presence of shear and that this complex flow pattern increased in velocity as the drum temperature approached the onset temperature for melting the PE material. With strong correlation between the rate of circulation and the temperature rise in the bed, the movement of particles was assumed to act in a convective heat transfer

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Product Design of Cohesive Powders – Mechanical Properties, Compression and Flow Behavior

Cited by 63 publications

References 70 publications

Effect of Particle Size and Cohesion on Powder Yielding and Flow

Effect of Particle Size and Cohesion on Powder Yielding and Flow

Analysis of industrial reactive powders flow properties at high temperature

Cohesive‐driven particle circulation in the solids conveying zone of a single‐screw extruder

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