Discrete element simulation of powder compaction in cold uniaxial pressing with low pressure

Rojek, Jerzy; Nosewicz, Szymon; JURCZAK, Kamila; Chmielewski, Marcin; Bochenek, Kamil; Pietrzak, K.

doi:10.1007/s40571-015-0093-0

Cited by 22 publications

(31 citation statements)

References 31 publications

(46 reference statements)

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“…Analogously to work performed in [20], a detailed investigation of interaction of two equal NiAl particles (with radii R = 10μm) under compression has been carried out using the two elastic contact models presented earlier. The purpose of this study was to compare the force-penetration relationships for different models and model parameters (Table 1).…”

Section: Numerical Results and Discussionmentioning

confidence: 99%

“…5) determined experimentally [20], a cylindrical container of diameter 200 μm has been filled with 1751 particles (Fig. 6).…”

Section: Numerical Results and Discussionmentioning

confidence: 99%

“…Figure 9 presents the evolution of relative density of NiAl specimen during initial powder compaction and pressureassisted sintering. Moreover, the graph shows the experimental results obtained by own studies, which have been widely described in [16,20,29]. The whole simulation has been divided into subsequent stages: loading, heating, sintering, cooling and unloading.…”

Section: Numerical Results and Discussionmentioning

confidence: 99%

“…where k s is the tangential stiffness described in [20], v rs is the relative tangential velocity and t is the time step. The tangential stiffness k s depends on the equivalent shear modulus G eff and the particle overlap h:…”

Section: Formulation Of Discrete Element Modelmentioning

confidence: 99%

“…Presented analysis concerns the relatively low values of external pressure and the hard and brittle NiAl material, thus the contribution of elastic deformation in the total one is a predominant. This effect has been studied in [20].…”

Section: Formulation Of Discrete Element Modelmentioning

confidence: 99%

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Application of the Hertz formulation in the discrete element model of pressure-assisted sintering

et al. 2017

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This paper presents the numerical modelling of initial powder compaction and pressure-assisted sintering performed by original viscoelastic discrete element model. The research is focused on the influence of the type of the model representing an elastic part of interparticle force. Two elastic contact models-linear and nonlinear Hertz modelhave been implemented and used to analyse interaction of NiAl powder particles during compaction and sintering process. Numerical models have been validated using own experimental results. Microscopic effects (particle penetration) and macroscopic changes (relative density) have been compared. It has been shown that although both models represent properly macroscopic behaviour of the material at the sintering process, the Hertz model produces the results closer to the real experimental ones during the initial compaction stage. Evaluation of macroscopic quantities enables implementation of the discrete element model in the framework of the multiscale modelling framework which is currently developed for sintering processes.

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Section: Numerical Results and Discussionmentioning

confidence: 99%

“…5) determined experimentally [20], a cylindrical container of diameter 200 μm has been filled with 1751 particles (Fig. 6).…”

Section: Numerical Results and Discussionmentioning

confidence: 99%

Section: Numerical Results and Discussionmentioning

confidence: 99%

Section: Formulation Of Discrete Element Modelmentioning

confidence: 99%

Section: Formulation Of Discrete Element Modelmentioning

confidence: 99%

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Application of the Hertz formulation in the discrete element model of pressure-assisted sintering

et al. 2017

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Convergence and stability analysis of the deformable discrete element method

Madan

Rojek

Nosewicz

2019

Numerical Meth Engineering

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Summary This work investigates numerical properties of the algorithm of the discrete element method (DEM) employing deformable circular disks presented in the authors' earlier publication. The new formulation called the deformable DEM (DDEM) enhances the standard DEM (SDEM) by introducing an additional (global) deformation mode caused by the stresses in the particles induced by the contact forces. An accurate computation of the contact forces would require an iterative solution of the implicit relationship between the contact forces and particle displacements. In order to preserve efficiency of the DEM, the new formulation has been adapted to the explicit time integration. It has been shown that the explicit DDEM algorithm is conditionally stable and there are two restrictions on its stability. Except for the limitation of the time step as in the SDEM, the stability in the DDEM is governed by the convergence criterion of the iterative solution of the contact forces. The convergence and stability limits have been determined analytically and numerically for selected regular and irregular configurations. It has also been found out that the critical time step in DDEM remains unchanged with respect to the SDEM.

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Critical time step for DEM simulations of dynamic systems using a Hertzian contact model

Burns

Piiroinen

Hanley

2019

Numerical Meth Engineering

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The discrete element method (DEM) typically uses an explicit numerical integration scheme to solve the equations of motion. However, like all explicit schemes, the scheme is only conditionally stable, with the stability determined by the size of the time step. Currently, there are no comprehensive techniques for estimating appropriate DEM time steps when a nonlinear contact interaction is used. It is common practice to apply a large factor of safety to these estimates to ensure stability, which unnecessarily increases the computational cost of these simulations. This work introduces an alternative framework for selecting a stable time step for nonlinear contact laws, specifically for the Hertz-Mindlin contact law. This approach uses the fact that the discretised equations of motion take the form of a nonlinear map and can be analysed as such. Using this framework, we analyse the effects of both system damping and the initial relative velocity of collision on the critical time step for a Hertz-Mindlin contact event between spherical particles.

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Discrete element simulation of powder compaction in cold uniaxial pressing with low pressure

Cited by 22 publications

References 31 publications

Application of the Hertz formulation in the discrete element model of pressure-assisted sintering

Application of the Hertz formulation in the discrete element model of pressure-assisted sintering

Convergence and stability analysis of the deformable discrete element method

Critical time step for DEM simulations of dynamic systems using a Hertzian contact model

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