Towards a mechanistic model for the interaction between plastically deforming particles under confined conditions: A numerical and analytical analysis

Abstract

Triaxial compression of plastically deforming particles was studied with the finite element method in order to identify the mechanisms that underlie their mechanical response under confined conditions. In addition to the established elastoplastic behaviour at small and intermediate strains, the coalescence of plastic zones centred at contacts resulted in a reduced stiffness, whereas a significantly increased stiffness was seen once the material displaced by plastic deformation filled the ambient void space, signifying the onset of a stage dominated by elastic volume reduction. Moreover, an analytical model for multiple simultaneous contacts was formulated, assuming that the deformed particle shape could be approximated by a truncated sphere and that the behaviour of each individual contact could be described in terms of a hardness. The thus obtained model exhibited a promising agreement with the numerical results.

An apparatus for confined triaxial testing of single particles

“…A FEM model developed and described by Frenning [11] for confined compression of single particles was used for comparison with the experimental results from the compression of CA particles. For this simulation, parameters corresponding to spherical particles with a diameter of 2 mm were used.…”

“…However, under uniaxial particle compression, there are two such contacts acting on the same particle. Even though these contacts do not impinge, the propagation of plastic deformation tend to lead to coalescence of plastically deformed zones at higher strains (see for example [11]), thus affecting the contact forces. Compared to the triaxial curves, the AF model assumes full plasticity and contact independence and hence becomes invalid in modelling triaxial compression at strain levels where contact impingement becomes significant, which also can be seen in Figure 10.…”

“…For example, Frenning [11] developed an analytical model for the micromechanical forces upon plastic deformation of particles that was validated using the FEM. Gonzalez and Cuitiño [12] attempted to overcome the restriction of independent contacts by the formulation of an analytical contact model for elastically deforming particles using an extension of the Hertz theory.…”

Towards a mechanistic contact model for elastoplastic particles at high relative densities

“…Comparison with FEM/DEM results indicated that a superior representation of the particle responses under compression was obtained when contact dependence was properly accounted for. As a first step towards a mechanistic model for the interaction between plastically deforming particles under confined conditions, a geometrical analysis of the deformed particle shape was made in terms of a truncated sphere whose radius increased to accommodate the displaced material [19], building on the work by Fischmeister and Arzt [2] and Montes et al [20].…”

Multiple Compression of Moist Spherical Elastic‐Plastic Zeolite 4A Granules

“…Later, Hanley et al [15] explained the failure of agglomerates at compressive loading using intricate numerical simulations of primary particles. The valuable work of Frenning [16] comparing the material behavior of different granules at different modes of compression using advanced simulation techniques has provided exceptional qualitative information regarding the simulation of particle behavior at compression. Several other researchers have also contributed to the existing knowledge of the material behavior of different types of granular materials and agglomerates under cyclic loading conditions.…”