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On discrete element modelling of compaction of powders with size ratio
KTH, Superseded Departments, Solid Mechanics.
KTH, Superseded Departments, Solid Mechanics.ORCID iD: 0000-0001-6232-8819
2004 (English)In: Computational materials science, ISSN 0927-0256, Vol. 31, 131-146 p.Article in journal (Refereed) Published
Abstract [en]

A numerical procedure, based on a discrete element method (DEM), for analysing cold compaction of spherical powders, is presented. In the numerical model, packing followed by compaction of up to 10,000 powder particles is simulated. Perfectly plastic material behaviour is assumed for convenience, but not for necessity, and as a result, local contacts between frictionless particles are described by a linear force–displacement relation. The numerical model is described in detail and its applicability to compaction problems of different complexity is discussed. Explicit results are presented for the case of isostatic compaction of spherical powders with size ratio and include applied pressure as function of densification as well as the evolution of contacts for individual particles. The present results are compared in detail with corresponding results from previous theoretical, experimental and numerical studies and the validity of fundamental assumptions made in previous theoretical analyses are discussed.

Place, publisher, year, edition, pages
2004. Vol. 31, 131-146 p.
Keyword [en]
Powder, Isostatic compaction, Discrete element modelling
National Category
Mechanical Engineering
URN: urn:nbn:se:kth:diva-6348DOI: 10.1016/j.commatsci.2004.02.005ISI: 000223950500012ScopusID: 2-s2.0-4344581627OAI: diva2:11036
QC 20101007 Available from: 2005-09-14 Created: 2005-09-14 Last updated: 2011-09-23Bibliographically approved
In thesis
1. Cold compaction of composite powders
Open this publication in new window or tab >>Cold compaction of composite powders
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Powder compaction is a production method commonly used in the manufacturing industry today. In order to minimize costly experiments and to optimize serial production of details several methods to analyze the powder compaction process are developed and used. One method is to use micromechanical analysis where the local description of contact between two individual particles is of great importance. In this dissertation a visco-plastic contact law has been used and further developed in order to understand the powder compaction process at packing, low relative density compaction up to high relative density compaction.

In order to relax some assumptions from previous theoretical studies simulation with the discrete element method (DEM) was performed. Up to 10.000 spherical particles were used in packing and early compaction simulation. It was found that rearrangement of particles is one of the major densification mechanisms in the early phases of compaction. At die compaction this effect of rearrangement was shown to be more pronounced than predicted from theoretical analyses. It was also found that the size ratio of particles is of importance when the number fraction of small particles in the compound is high.

The finite element method has been used for numerical analyses to investigate the local contact problem between two particles when self-similarity no longer prevail. Based on the numerical results a suggestion for an approximate compliance relation was made. With this approximate formula the local compliance behaviour between two dissimilar particles was analysed. These findings are directly applicable to simulations with the discrete element method. Finally, an investigation using the finite element method to evaluate the range of the accuracy for theoretical and approximate compliance formula has been done with compounds of different regular lattices. It was found that the range of accuracy is much dependent on the number of contacts within the lattices, specially new forming contacts during the compaction.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. vii, 15 p.
Trita-HFL. Report / Royal Institute of Technology, Solid mechanics, ISSN 1654-1472 ; 0389
micromechanical modelling, composite powders, descrete element method
National Category
Mechanical Engineering
urn:nbn:se:kth:diva-417 (URN)
Public defence
2005-09-23, Sal B2, Brinellvägen 23, Stockholm, 10:00

QC 20101007

Available from: 2005-09-14 Created: 2005-09-14 Last updated: 2013-01-14Bibliographically approved

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Skrinjar, OlleLarsson, Per-Lennart
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