A Multiparticle Simulation of powder Compaction Using Finite Element Discretization of Individualparticles
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A Multiparticle Simulation of Powder Compaction Using Finite Element Discretization of Individual Particles Antonios Zavaliangos Department of Materials Engineering Drexel University, Philadelphia, PA19010 ABSTRACT Discrete element studies of powder compaction have become popular recently. A disadvantage of this technique is the need for simplification of the inter-particle contact behavior which limit the applicability of DEM to small relative densities. To overcome this problem, we analyze the compaction of powder by a 2-D finite element study of the compaction of 400 particles, each of which is discretized at a sufficient level to provide adequate detail of the interparticle interaction. The material is modeled as elastic-perfectly plastic. Simulations show that: (a) there is an effect of interparticle friction on the macroscopic response in the earlier stages of compaction, (b) there is significant rearrangement even in highly constrained compaction modes, (c) the absence of friction promotes inhomogeneous deformation in the compact, and (d) conditions for fragmentation develop in particles with loose lateral constrains. INTRODUCTION Particulate processing, including compaction and sintering is a key technology for the production of typical and advanced engineering materials. The mechanical behavior of powders in compaction has been studied over the years primarily by continuum models [1-6]. Microstructural characteristics are introduced via a small number of internal variables that evolve during the process. Practically only one variable is usually considered, namely the relative density (deformation resistance is used less frequently). Phenomenological models are usually motivated by micromechanical models, that provide a means to derive macroscopic model parameters from information on a smaller length scale (particle level). The micro-to-macro transition is performed usually by homogenization techniques. For example, macroscopic compaction models can be derived by considering the interaction of two spheres under a central force [7, 8]. Micromechanical methods offer a systematic approach to describing the behavior of porous materials, but their predictive capability can be limited. The accuracy of the solution of the unit problem and the homogenization technique involve significant assumptions that are required for the solutions to be tractable. Moreover, micromechanical models address only plastic deformation while rearrangement and particle fragmentation are often ignored. In an effort to provide a better basis for continuum models and to improve our understanding for the physical phenomena during compaction at the particle level, attention has been recently focused on discrete element methods (DEM). DEM stems from work in soil mechanics [9] and involves the numerical simulation of individual particles that interact, based on a set of prescribed contact conditions. It can provide significant information on particle motion, contact forces, and several macroscopic quantities in an assembly of particles subject
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