The percolation behavior of composites comprising complex-shaped particles is a recurrent problem in materials science. Previous studies focused on the symmetric particles such as spheres, ellipsoids, spherocylinders,...
详细信息
The percolation behavior of composites comprising complex-shaped particles is a recurrent problem in materials science. Previous studies focused on the symmetric particles such as spheres, ellipsoids, spherocylinders, etc. The continuum percolation of a family of single axial asymmetric ovoids with tapering parameter T and aspect-ratio c/a is studied here. The geometrical properties and numerical contact detection algorithm of these ovoids are proposed firstly. Using the Monte Carlo finite-size-scaling method, the percolation threshold phi(c) of the systems comprising congruent overlapping ovoids is further determined. For a given T, phi(c) shows an initially increasing and then decreasing trend with the increasing c/a. Moreover, the value of phi(c), at the fixed c/a decreases with the increasing [T] and this trend will be more obvious with the decreasing c/a. Finally, an analytical formula is proposed to quantify the effect of ovoid's morphology, characterized by the dimensionless excluded volume of ovoid, on the percolation thresholds. (C) 2019 Elsevier B.V. All rights reserved.
Particulate composites are composed of random packing of polydispersed particles, such as cementitious composites. The packing behavior of particles plays an important role in the mesostructural evolution of particula...
详细信息
Particulate composites are composed of random packing of polydispersed particles, such as cementitious composites. The packing behavior of particles plays an important role in the mesostructural evolution of particulate composites. The preponderance of previous works has focused on the random packing of spherical, cylindrical or elliptical particles, and little is known about ellipsoidal particles. In the present work, a contact detection algorithm of ellipsoids is presented in detail, which can quantitatively describe relative positions of ellipsoids in a three-dimensional space. The accuracy and efficiency of the algorithm are tested and compared with algorithms developed in previous literature, and its reliability is verified by a random sequential packing model of polydispersed ellipsoids with semi-periodic boundary conditions. Moreover, the algorithm is applied to simulate a mesostructure model of cementitious composites. By means of stereological tools and section analysis technologies, the mesostructure of cementitious composites is quantitatively characterized. Finally, the reliability of the statistical results from the present methodology is verified by valid experimental and theoretical results. (c) 2012 Elsevier B.V. All rights reserved.
Purpose - contact interaction and contactdetection (CD) remain key components of any discontinua simulations. The methods of discontinua include combined finite-discrete element method (FDEM), discrete element method...
详细信息
Purpose - contact interaction and contactdetection (CD) remain key components of any discontinua simulations. The methods of discontinua include combined finite-discrete element method (FDEM), discrete element method, molecular dynamics, etc. In recent years, a number of CD algorithms have been developed, such as Munjiza-Rougier (MR), Munjiza-Rougier-Schiava (MR-S), Munjiza-No Binary Search (NBS), Balanced Binary Tree Schiava (BBTS), 3D Discontinuous Deformation Analysis and many others. This work aims to conduct a numerical comparison of certain algorithms often used in FDEM for bodies of the same size. These include MR, MR-S, NBS and BBTS algorithms. Design/methodology/approach - Computational simulations were used in this work. Findings - In discrete element simulations where particles are introduced randomly or in which the relative position between particles is constantly changing, the MR and MR-S algorithms present an advantage in terms of CD times. Originality/value - This paper presents a detailed comparison between CD algorithms. The comparisons are performed for problem cases with different lattices and distributions of particles in discrete element simulations. The comparison includes algorithms that have not been evaluated between them. Also, two new algorithms are presented in the paper, MR-S and BBTS.
The combined finite-discrete-element method (FDEM) has made a groundbreaking progress in the computation of contact interaction. However, FDEM has a strict requirement on the element type, and the simulation result ma...
详细信息
The combined finite-discrete-element method (FDEM) has made a groundbreaking progress in the computation of contact interaction. However, FDEM has a strict requirement on the element type, and the simulation result may be inconsistent due to a deficiency of physical meaning of the potential function. To address this problem, a new 3D discrete-element method based on a distance potential is proposed for a system consisting of a large number of arbitrary convex polyhedral elements. In this approach, a well-defined distance potential is proposed as a function of the penetration between the contact pairs. It exhibits a clear physical meaning and a precise measurement of the embedding between the elements in contact. The newly presented method provides a holonomic and accurate contact interaction without being influenced by the element shape. Therefore, the restraint of the element type in FDEM is removed and the proposed method can be used for arbitrary convex polyhedrons. In addition, an improved contact detection algorithm for non-uniform block discrete elements is provided to overcome the constraint of elements with the same size in the Munjiza-No Binary Search contactdetection method. The new approach retains the merits of the FDEM and avoids its deficiencies. It is validated with well-known benchmark examples including an impact simulation, a friction experiment, a joint structure of a sliding rock mass, pillar impact, block accumulation, and analysis for the failure process of wedge slope. The results of this proposed method are in excellent agreement with the existing experimental measurements and analytical solutions.
An inter-ellipsoid contact detection algorithm was developed and used for simulating the behaviour of assemblies of ellipsoid-shaped particles using the well-known discrete element method (DEM). The contactalgorithm ...
详细信息
An inter-ellipsoid contact detection algorithm was developed and used for simulating the behaviour of assemblies of ellipsoid-shaped particles using the well-known discrete element method (DEM). The contactalgorithm was implemented in the modified version of the DEM program TRUBAL originally written to simulate the behaviour of assemblies of spheres. The modified program was used to perform deviatoric and axisymmetric compression tests on a 1000 prolate spheroid assembly in periodic space. The obtained stress-strain-dilation curves conform with the experimental evidence both qualitatively and quantitatively. (C) 1999 Elsevier Science Ltd. All rights reserved.
暂无评论