Slow stress relaxation behavior of cohesive powders

Imole, Olukayode Isaiah; Paulick, M.; Magnanimo, Vanessa; Morgenmeyer, Martin; Ramaioli, Marco; Montes, Bruno E. Chavez; Kwade, Arno; Luding, Stefan

doi:10.1016/j.powtec.2015.12.023

Cited by 17 publications

(18 citation statements)

References 45 publications

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“…On the contrary, in the indirect devices, the shear zone develops according to the applied state of stress. The most common indirect devices are the uniaxial compression tester (Russell et al, 2014;Thakur et al, 2014;Imole et al, 2016) and bi-axial shear box Feise and Schwedes, 1995). Direct devices can be further categorised into two sub-groups: translational and rotational.…”

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

Self Cite

View full text Add to dashboard Cite

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“…Raw material properties often have substantial impact on the performance of the manufacturing process [18][19][20]. Identifying the relationship between raw material properties and process performance is critical for determining the effect of material property variations on downstream processes [21].…”

Section: Introductionmentioning

confidence: 99%

Predicting feeder performance based on material flow properties

Wang

Muzzio

et al. 2017

Powder Technology

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Purpose: Accurate and consistent delivery of materials by well-designed feeders ensures overall process stability. Importantly, feeding performance is strongly dependent on material flow properties. The purpose of this study is to develop a methodology that identifies predictive correlation between material flow properties and feeder performance. Method: The proposed methodology includes techniques to characterize material flow properties, methods to quantify feeding performance of a loss-in-weight feeder, and predictive multivariate analysis. Two approaches to correlate feeding performance and material flow properties were examined in the study: principal component analysis, followed by similarity scoring (PCA-SS), and partial least squares regression (PLSR). Results: Experimental results showed that selection of the optimal feeder screw to achieve optimum feeding performance is heavily dependent on material flow properties. Both approaches to predict feeding performance based on material properties were validated. In addition, a strong correlation between the initial feed factor of each material and its flow properties were observed. Conclusion: The work presented here has demonstrated an efficient approach to correlate material properties with gravimetric feeder performance. This approach is especially powerful in the early phase of process and product development, when the amount of a material is limited.

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“…The relaxation of the shear stress in the small cell is slightly greater than in the big cell. The influence of the aspect ratio of the experimental setup has been previously shown to affect the relaxation behaviour by a different initial density of the powder bed [14], but in this setup, the stiffness and sheared surface are also different.…”

Section: Behaviour Of the Relaxationmentioning

confidence: 97%

Slow and intermittent stress relaxation of biomass granular media

et al. 2021

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In the present work, the relaxation of several wood powders has been investigated in an annular shear cell. It is found that the slow logarithmic relaxation commonly observed for various materials including granular materials is interrupted by large events. Their frequency and amplitude are investigated with respect to particle size and stress-history by measuring stresses and strain. These large events during the relaxation appear to be controlled by the deformation. The coarser the particles are, the bigger is the deformation of the powder bed between two fast relaxation events and during the event.

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Slow stress relaxation behavior of cohesive powders

Cited by 17 publications

References 45 publications

Effect of Particle Size and Cohesion on Powder Yielding and Flow

Effect of Particle Size and Cohesion on Powder Yielding and Flow

Predicting feeder performance based on material flow properties

Slow and intermittent stress relaxation of biomass granular media

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