Micro-Deformation Mechanism of Shear Banding Process Based on Modified Distinct Element Method

Iwashita, K.; Oda, Masanobu

doi:10.2208/journalam.2.401

Cited by 56 publications

(76 citation statements)

References 23 publications

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“…the stiffness is constant during plastic deformation, which confirms the perfectly plastic model, Eq. (35). This model can be recommended for DEM as a simple force-displacement relationship for loading of ideally plastic spherical granules.…”

Section: Discussionmentioning

confidence: 99%

“…According to Eq. (35), that means that perfectly plastic deformation occurs when A el = 0 and A K = A pl . Figure 17 shows the effect of the granule size on the force-displacement behaviour.…”

Section: Materials Parametersmentioning

confidence: 99%

“…Eqs. (34) and (35) can be used to develop the equation for the strength of dominantly plastic granules:…”

Section: Materials Parametersmentioning

confidence: 99%

“…In the last ten-fifteen years, these methods found many applications in the mechanics of bulk materials, i.e. flow behaviour and discharge of silos [8,49,50], filling and packing [111], shearing [25,35,47,61,103], heap formation [13,36,65], bed configuration and loading conditions in fall mills [63,69,105], compression behaviour [68,78], mixing and transportation [12,27,44,52,54,107], fluidised bed processes [31,40,41,58,66,90,102,104,110,112], heat exchange processes [41,50].…”

Section: Introductionmentioning

confidence: 99%

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Energy absorption during compression and impact of dry elastic-plastic spherical granules

et al. 2010

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The discrete modelling and understanding of the particle dynamics in fluidized bed apparatuses, mixers, mills and others are based on the knowledge about the physical properties of particles and their mechanical behaviour during slow, fast and repeated stressing. In this paper model parameters (modulus of elasticity, stiffness, yield pressure, restitution coefficient and strength) of spherical granules ( γ -Al 2 O 3 , zeolites 4A and 13X, sodium benzoate) with different mechanical behaviour have been measured by single particle compression and impact tests. Starting with the elastic compression behaviour of granules as described by Hertz theory, a new contact model was developed to describe the force-displacement behaviour of elastic-plastic granules. The aim of this work is to understand the energy absorption during compression (slow stressing velocity of 0.02 mm/s) and impact (the impact velocity of 0.5-4.5 m/s) of granules. For all examined granules the estimated energy absorption during the impact is found to be far lower than that during compression. Moreover, the measured restitution coefficient is independent of the impact velocity in the examined range and independent of the load intensity by compression (i.e. maximum compressive load). In the case of repeated loading with a constant load amplitude, the granules show cyclic hardening with increasing restitution coefficient up to a certain saturation in the plastic deformation. A model was proposed to describe the increase of the contact stiffness with the number of cycles. When the load amplitude is subsequently increased, further plastic deformation takes place and the restitution coefficient strongly decreases.

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Section: Discussionmentioning

confidence: 99%

Section: Materials Parametersmentioning

confidence: 99%

“…Eqs. (34) and (35) can be used to develop the equation for the strength of dominantly plastic granules:…”

Section: Materials Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Energy absorption during compression and impact of dry elastic-plastic spherical granules

et al. 2010

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“…Cundall (1989); Iwashita and Oda (2000) for frictional granular materials or Hagenmuller et al (2015) for snow), the grains involved in the DE model developed in this study should not be regarded as snow grains, and that both r wl and r are only discretization scales whose choice will result from a compromise between resolution and computational cost as classically done to model concrete fracture (Hentz et al, 2004). We consider here a meter-scale model where the advantage of the DE method is its ability to mimic the poorly known mechanical response of the weak layer and to account for the different modes of failure displayed by snow (shear, compression, tension).…”

Section: Motivation and Objectivesmentioning

confidence: 99%

Modeling of crack propagation in weak snowpack layers using the discrete element method

Gaume¹,

Herwijnen²,

Chambon

et al. 2015

The Cryosphere

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Abstract. Dry-snow slab avalanches are generally caused by a sequence of fracture processes including (1) failure initiation in a weak snow layer underlying a cohesive slab, (2) crack propagation within the weak layer and (3) tensile fracture through the slab which leads to its detachment. During the past decades, theoretical and experimental work has gradually led to a better understanding of the fracture process in snow involving the collapse of the structure in the weak layer during fracture. This now allows us to better model failure initiation and the onset of crack propagation, i.e., to estimate the critical length required for crack propagation. On the other hand, our understanding of dynamic crack propagation and fracture arrest propensity is still very limited.To shed more light on this issue, we performed numerical propagation saw test (PST) experiments applying the discrete element (DE) method and compared the numerical results with field measurements based on particle tracking. The goal is to investigate the influence of weak layer failure and the mechanical properties of the slab on crack propagation and fracture arrest propensity. Crack propagation speeds and distances before fracture arrest were derived from the DE simulations for different snowpack configurations and mechanical properties. Then, in order to compare the numerical and experimental results, the slab mechanical properties (Young's modulus and strength) which are not measured in the field were derived from density. The simulations nicely reproduced the process of crack propagation observed in field PSTs. Finally, the mechanical processes at play were analyzed in depth which led to suggestions for minimum column length in field PSTs.

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Finite strain analysis of nonuniform deformation inside shear bands in sands

Chupin

Rechenmacher

Abedi

2011

Num Anal Meth Geomechanics

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SUMMARYA methodology has been developed to extend the incremental (Eulerian) Digital Image Correlation (DIC) technique to enable a Lagrangian-based large-strain analysis framework to examine the nature of strain and kinematic nonuniformity within shear bands in sands. Plane strain compression tests are performed on dense sands in an apparatus that promotes unconstrained persistent shear band formation. DIC is used to capture incremental, grain-scale displacements in and around shear bands. The performance of the developed accumulation algorithm is validated by comparing accumulated displacements with two sources of reference measurements. A comparison between large and infinitesimal rotation is performed, demonstrating the nature of straining within shear bands in sands and the necessity of using a finite strain formulation to characterize ensuing behavior. Volumetric strain variation along the shear band is analyzed throughout macroscopic postpeak deformation. During softening, volumetric activity within the shear band is purely dilative. During the global critical state, the shear band material is seen on the average to deform at zero volumetric strain; however, locally, the sand is seen to exhibit significant nonzero volumetric strain, putting into question the current definition of critical state. At the softening-critical state transition, a spatially periodic pattern of alternating contraction and dilation along the shear band is evidenced, and a preliminary evaluation indicates that the periodicity appears to be a physical phenomenon dictated only in part by median grain size.

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Micro-Deformation Mechanism of Shear Banding Process Based on Modified Distinct Element Method

Cited by 56 publications

References 23 publications

Energy absorption during compression and impact of dry elastic-plastic spherical granules

Energy absorption during compression and impact of dry elastic-plastic spherical granules

Modeling of crack propagation in weak snowpack layers using the discrete element method

Finite strain analysis of nonuniform deformation inside shear bands in sands

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