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Số người truy cập: 39,646,157

 Numerical modeling and homogenisation of soft granular media
Tác giả hoặc Nhóm tác giả: Thanh Hai NGUYEN, Farhang RADJA, Saeid NEZAMABADI
Nơi đăng: 25th ALERT Workshop, ALERT Geomaterials, France; Số: ISBN: 978-2-9542517-2-1;Từ->đến trang: 35;Năm: 2014
Lĩnh vực: Kỹ thuật; Loại: Báo cáo; Thể loại: Quốc tế
TÓM TẮT

ABSTRACT
Soft-particle materials include colloidal pastes, vesicles, many powders, microgels and suspensions, indicating their diversity and technological importance. These materials share the common feature of being composed of well-defined particles that can undergo large deformations without rupture. In this respect, they differ from hard-particle materials with their plastic behaviour mainly governed by particle rearrangements and frictional sliding. Soft particles can reach high packing fractions by particle shape change and still flow plastically. The compaction, volume change behaviour under shearing and the properties of the resulting complex textures in soft packings above the random close packing state have basically remained unexplored due to the lack of proper numerical and experimental tools. The Discrete Element Methods (DEM) are widely used for modeling particle assemblies due to its ability to take into account different loading conditions, particle size distributions and physical properties of the particles. However, the DEM is not suitable for simulating realistic behaviour at the sub-particle scale, including large deformations. To model the mechanical properties of soft particles and their mutual interactions, a new methodology is proposed on an implicit formalism of Material Point Method (MPM) coupled with the Contact Dynamics (CD) [1]. In MPM, each particle is discretized by a collection of material points. The information carried by the material points is projected onto a background mesh, where equations of motion are solved. The mesh solution is then used to update the material points. The implicit formulation allows for unconditional numerical stability and efficient coupling with implicit modelling of unilateral contacts and friction between the particles. This implicit MPM-CD model is implemented in a manner that the contact variables (velocity, force...) can be computed simultaneously with bulk variables. This technique MPM is compared with a simpler model in which deformable grains represent by an assembly of primary particles interacting by attractive forces and simulated by the CD method. We present an investigation of the compaction process of 2D soft-particle assemblies by means of these proposed models. References 1. S. Nezamabadi, F. Radjai, J. Averseng and J.-Y. Delenne, “Modelling soft-particle materials”, in Proceedings of the Geomechanics from Micro to Macro, Cambridge, 2014, edited by Soga et al., pp. 43-48.
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