An elastic/viscoplastic model of the fibre network stress in wet pressing: Part 1

Lobosco, Vinicius; Kaul, Vikram

doi:10.3183/npprj-2001-16-01-p012-017

Cited by 11 publications

(12 citation statements)

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“…Moreover, a number of recent studies have suggested that the solid stress must be rate-dependent in order to reproduce the observed dewatering and flow-induced compaction of pulp suspensions and capillary rise through paper sheets. 15,27,28 These studies have accounted for this rate dependence by extending the description of the solid stress to include an effective bulk viscosity of the network, with some precedence existing in earlier work, 16,26,[29][30][31][32] or by analogy with the generic shear viscosity expected for a two-phase medium 33 (alternative perspectives and models also exist 34 ). Thus, pulp suspensions appear to require an unconventional viscoplastic solid stress.…”

Section: Introductionmentioning

confidence: 99%

On two‐phase modeling of dewatering pulp suspensions

et al. 2021

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An experimental study of the dewatering of wood-pulp fiber suspensions by uniaxial compression is presented, to rationalize their dewatering dynamics within a twophase framework. Twenty-seven pulp suspensions are examined, encompassing materials with different origins, preparation methodologies, and secondary treatments. For each suspension in this library, the network permeability and compressive yield stress are calibrated at low rates of dewatering. Faster compressions are then used to verify that a solid bulk viscosity is essential to match two-phase model predictions with experimental observations, and to parameterize its magnitude. By comparing the results with a suspension of nylon fibers, we demonstrate that none of the wood-pulp suspensions behave like an idealized fibrous porous medium. Nevertheless, the properties of pulp fiber networks can be reconciled within a two-phase framework, and comparisons made between different wood-pulp suspensions and between wood-pulp and nylon fibers, by appealing to potential microstructural origins of their macroscopic behavior.

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Section: Introductionmentioning

confidence: 99%

On two‐phase modeling of dewatering pulp suspensions

et al. 2021

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“…This implies that absence of (solid) stress means absence of strain and that the stress-strain relationship is the same in compression and expansion phase. However, compressed wet paper can experience complicated permanent and semi-permanent deformations, see for instance (Nilson and Larson, 1968;Lobosco and Kaul, 2001). In other words, after releasing of pressure, paper does not regain (or at least not immediately) its original thickness.…”

Section: Plastic Deformation Of Papermentioning

confidence: 96%

Analysis of Wet Pressing of Paper: The Three-Phase Model. Part II: Compressible Air Case

2007

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In this study we consider a model of wet pressing of paper. We use the techniques and results from the first part of this paper, where a simplified model is studied in details. The model is, using suitable transformation, rewritten in the standard parabolic-hyperbolic form. Numerical solution for typical example is given and the effects of plastic deformations of paper are investigated. Finally, the model is employed to adres the problem of choosing an optimal pressing regime.

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“…so thatΛ(φ) is a φ-dependent bulk viscosity, which represents a generic form of constitutive behaviour of two-phase solid-liquid materials after linearisation in the solid compression rate [19] (see [21] for a more elaborate constitutive relation for paper-making fibre suspensions which is nonlinear in the compression rate). The compressive yield stress p Y (φ) is typically measured experimentally.…”

Section: Equations Of Motion In the Shunting Zonementioning

confidence: 99%

Dewatering saturated, networked suspensions with a screw press

et al. 2019

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A model is presented for the dewatering of a saturated two-phase medium in a screw press. The model accounts for the detailed two-phase rheological behaviour of the pressed material and splits the press into two zones, an initial well-mixed constant-pressure region followed by an axial transport region in which the total pressure steadily increases. In this latter region, a slowly-varying helical coordinate transformation is introduced to help reduce the dynamics to an annular bi-axial compression of the two-phase medium. Unlike previous modeling, the transition point between the two zones is determined self-consistently, rather than set a priori, and the pressure along the length of the press is deduced from the rheology of the two-phase flow rather than averaging the two-phase dynamics over a cross-section of the press. The model is compared to experimental observations of the dewatering of a paper-making fibre suspension and of a clay slurry, and is shown to reproduce operational data.

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An elastic/viscoplastic model of the fibre network stress in wet pressing: Part 1

Cited by 11 publications

References 0 publications

On two‐phase modeling of dewatering pulp suspensions

On two‐phase modeling of dewatering pulp suspensions

Analysis of Wet Pressing of Paper: The Three-Phase Model. Part II: Compressible Air Case

Dewatering saturated, networked suspensions with a screw press

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