检索结果-内蒙古大学图书馆

Interaction of Soil Arching under Trapdoor Condition: Insights from 2D discrete-element Analysis

INTERNATIONAL JOURNAL OF GEOMECHANICS 2022年第6期22卷 04022066-04022066页

作者： Bao, Ning Wei, Jing Chen, Jian-feng Sun, Rui Tongji Univ Coll Civil Engn Dept Geotech Engn Shanghai 200092 Peoples R China Beijing Jiaotong Univ Sch Civil Engn Beijing 100044 Peoples R China

The trapdoor/trapdoor-like model test has been widely utilized to investigate the evolution of soil arching. However, the primary focus of previous studies has been on the mechanical and deformation behaviors of the arching field under the single-trapdoor condition, while the interaction of soil arching between adjacent trapdoors has not been well understood. In this paper, a series of discrete numerical models based on the plane-strain laboratory trapdoor test were established to investigate the interaction effect, with respect to stress redistributions, particle movement, anisotropy of contact forces, and energy regime. The effects of motion mode, namely the simultaneous and nonsimultaneous movement, and the spacing (B) between adjacent trapdoors on the arching performance were examined. The numerical results revealed that the simultaneous movement of twin trapdoor slightly influences earth pressures resting on the surface of both trapdoors. The deformation pattern is deeply influenced by a narrow spacing of 0.25B and characterized by two arching fields interacting with each other, resulting in a noticeable subsidence at the crest. The subsequent lowering of the second-lowered trapdoor under the nonsimultaneous movement condition increases pressures resting on the first-lowered trapdoor, yields additional settlement within the former arching field, and distorts adjacent arched force chains. An increase in spacing from 0.25B to 1B is beneficial for reducing the pressure increment, decreasing the arching deformations, minimizing the rotation of the major principal direction, and decreasing the friction energy distribution density above the stationary supports.

关键词： Interaction of soil arching Trapdoor discrete-element method Earth pressure Force chain Energy regime

来源：评论

学校读者我要写书评

暂无评论

Simulation of particulate fouling at a microchannel entrance region

引用

MICROFLUIDICS AND NANOFLUIDICS 2015年第2期18卷 253-265页

作者： Marshall, Jeffrey S. Renjitham, Simtha Univ Vermont Sch Engn Burlington VT 05405 USA

A computational study is reported on the dynamics of particles near the entrance of a microchannel, as used in microfluidic flow systems. The collision of particles with fins separating the microchannels in these entrance regions makes them particularly susceptible to particle fouling. The study employs a soft-sphere discrete-element method with van der Waals and electric double-layer forces between the particles and the wall. A multi-block-structured grid fit to the flow domain boundaries is used to compute the fluid velocity field using a finite-volume method. The fluid flow is interpolated onto a Cartesian grid for efficient flow field interpolation at the particle locations, and a level-set method is used to represent the flow field boundaries in the particle computation. Particles adhering to the upstream face of the fin separating two microchannels are found to form clusters, which are pulled laterally by the stagnation-point flow near the fin. Even under conditions where the adhesion is sufficiently strong that there is little or no particle rolling on the fin face, the particles are still removed from the fin due to collisions with other particles. Individual particles are removed quickly from the fin face due to collision with upstream particles, whereas particle clusters have sufficient adhesion force with the fin surface that they can withstand collision with other particles for longer periods of time before they are removed in a cascade-like process.

关键词： Microchannel fouling discrete-element method Particle adhesion Entrance region

来源：评论

学校读者我要写书评

暂无评论

Contact impingement in packings of elastic-plastic spheres, application to powder compaction

引用

INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES 2012年第1期61卷 32-43页

作者： Harthong, Barthelemy Jerier, Jean-Francois Richefeu, Vincent Chareyre, Bruno Doremus, Pierre Imbault, Didier Donze, Frederic-Victor Univ Grenoble 1 Grenoble INP UMR 5521 Lab Sols F-38041 Grenoble 9 France Queensland Ctr Adv Technol CSIRO Pullenvale 4069 Australia

High-density compaction of ductile powder particles is characterized by a sharp increase of the interparticle normal contact force. This is due to both complex contact interactions and plastic incompressibility of the particle constitutive material. A DEM model (OPEN-DEM YADE) using an interaction force-law reproducing this increase has been developed to simulate high-density compaction of ductile powders. Its formulation is derived from a Finite element method model (ABAQUS). Macroscopic stresses resulting from compaction tests carried out on a random assembly of spherical grains were computed with both models and then compared. A good agreement between the stress-density curves confirmed the accuracy of the DEM formulation. However, the role of the grain deformation may not be well described using DEM since it is based on an assumption of overlapping rigid particles but allows low calculation costs. To highlight the role of this deformation process, a detailed FEM-based analysis of the influence of contact impingement on the normal contact force is thus presented. It explores the mechanisms of stress transmission between contact zones and quantifies the appearance of contact interactions in terms of both indentation depth and relative density. Results show that contact impingement cannot be neglected at a relative density as low as 0.7 if a local, contact-scale analysis is aimed for (such as density distribution for instance). In such a case, previous models like the one proposed by Storakers and co-authors, should be used with care. The local solid fraction provides a correct local description of both contact interactions and plastic incompressibility of the constitutive material of the grains up to the maximum density. This would allow the DEM to be successfully applied to large-scale simulations of high-density compaction. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.

关键词： Granular materials Powder compaction High density Contact model discrete-element method Finite-element method

来源：评论

学校读者我要写书评

暂无评论

Investigation of optimum design for nanoparticle dispersion in centrifugal bead mill using DEM-CFD simulation

引用

ADVANCED POWDER TECHNOLOGY 2019年第5期30卷 1034-1042页

作者： Nagata, Yu Minagawa, Masaya Hisatomi, Shosei Tsunazawa, Yuki Okuyama, Kyoko Iwamoto, Motonori Sekine, Yasuyoshi Tokoro, Chiharu Waseda Univ Grad Sch Creat Sci & Engn Tokyo 1698555 Japan Geol Survey Japan Natl Inst Adv Ind Sci & Technol AIST Ibaraki 3058567 Japan Nippon Coke & Engn Co Ltd Powder Technol Ctr Tochigi City Tochigi 3288503 Japan Waseda Univ Fac Sci & Engn Tokyo 1698555 Japan

A bead mill is commonly used to produce nanomaterials. The design of the bead mill rotor is an important factor in efficient nanomaterial production to avoid re-agglomeration. We investigated the effect of bead-mill rotor shape on the dispersion state using experimental tests and the discrete-element method (DEM) coupled with computational fluid dynamics (CFD) simulations. Experimental results using TiO2 in the bead mill showed that the high rotor rotation speed caused TiO2 particles re-agglomeration, and a sharp particle-size distribution was obtained by dispersion with a mill with a wide gap between the rotor and the chamber. To evaluate the dispersion performance, bead collisions were analyzed using the DEM-CFD simulation. The simulation results indicated that an increase in bead-collision energy lead to damage of the TiO2 primary particles and re-agglomeration at a high rotation speed. A uniform dispersion was achieved when the frequency of high-energy collision between the particle and wall decreased and a small standard deviation of the collision energy frequency was obtained by the mill with a wide gap. These simulation results correlate with the experimental results. Therefore, this study shows that the DEM-CFD simulation could contribute to an appropriate rotor design for uniform dispersion. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

关键词： discrete-element method Bead mill Dispersion Collision energy Titanium particle

来源：评论

学校读者我要写书评

暂无评论

Quantitative Comparison of Two-Dimensional and Three-Dimensional discrete-element Simulations of Nominally Two-Dimensional Shear Flow

引用

INTERNATIONAL JOURNAL OF GEOMECHANICS 2013年第3期13卷 205-212页

作者： Fleischmann, J. A. Plesha, M. E. Drugan, W. J. Univ Wisconsin Rock Cty Dept Engn Janesville WI 53546 USA Univ Wisconsin Dept Engn Phys Madison WI 53706 USA

Results obtained from numerical simulations of direct (or ring) shear tests on ASTM standard graded (Ottawa) sand using the discrete-element method with periodic boundary conditions in both two and three dimensions are reported. The data obtained from these simulations are quantitatively compared to experimental data for ASTM standard graded sand. The results show that the three-dimensional (3D) effects of nonplanar interparticle contact forces and particle motion are significant in the 3D discrete-element method simulations, even during nominally two-dimensional (2D) shear flow. Moreover, the 3D discrete-element method simulations accurately predict the peak and residual friction angles of ASTM standard graded sand. On the other hand, the 2D discrete-element method simulations fail to accurately predict the peak and residual friction angles. It is argued that the failure of the 2D discrete-element method simulations and the success of the 3D discrete-element method simulations in providing quantitatively accurate predictions of peak and residual friction angles are attributable largely to the respective absence or presence of 3D effects, including nonplanar interparticle contact forces and nonplanar particle motion, in these discrete-element method simulations. (C) 2013 American Society of Civil Engineers.

关键词： DEM discrete-element method Three dimensional Two dimensional Comparison Direct shear Ottawa sand

来源：评论

学校读者我要写书评

暂无评论

Three-Dimensional Simulation of Aggregate and Asphalt Mixture Using Parameterized Shape and Size Gradation

引用

JOURNAL OF MATERIALS IN CIVIL ENGINEERING 2019年第3期31卷

作者： Li, Jue Zhang, Junhui Qian, Guoping Zheng, Jianlong Zhang, Yuqing Changsha Univ Sci & Technol Natl Engn Lab Highway Maintenance Technol Changsha 410205 Hunan Peoples R China Aston Univ Sch Engn & Appl Sci Aston Inst Mat Res Birmingham B4 7ET W Midlands England

Aggregate occupies at least three-quarters of the volume of asphalt mixture and can significantly affect the performance of pavement. The geometrical morphology influences the slippage and interlock among aggregates for resisting and distributing applied loads. In recent years, the discrete-element method (DEM) has been employed for simulation of asphalt mixture structure. This paper introduces an approach for simulation of aggregate and asphalt mixtures using parameterized shape and size gradation. Both the plane geometry factor (PGF) and the section aspect ratio (SAR) were employed to describe the three-dimensional (3D) geometric characteristics of aggregates. A numerical technique of aggregate models was implemented with probabilistic parameters depending on statistical results of PGFs and SARs. The 3D numerical model of asphalt mixtures was assembled with three different components, and was validated by uniaxial compression tests via comparison with the laboratory result. It was found that the PGF and SAR are appropriate to describe the three-dimensional features of aggregate shapes, because a simplified space object can be described by a two-dimensional (2D) graphical projection and a vector scalar corresponding to the space vector. Probability distribution curves of PGFs and SARs between coarse aggregates were in concordance with the Gauss-type function, because their correlation coefficients were all greater than 95%. It was verified that the developed clumping algorithm of aggregates was reasonable in terms of the shape and size gradation. Based on the parallel-bond model and Burger's model, the results of virtual tests were in good agreement with those of laboratory uniaxial tests. The angularity (PGF) of aggregates has a beneficial effect on the strength and stability of asphalt mixtures, whereas the flat-elongated feature (SAR) has a negative effect on the strength and stability of asphalt mixtures.

关键词： Asphalt mixtures Irregular aggregates Three-dimensional simulation discrete-element method Parameterized shape

来源：评论

学校读者我要写书评

暂无评论

Experimental, continuum- and DEM-based velocities in a flat-bottomed bin

引用

POWDER TECHNOLOGY 2021年 377卷 297-307页

作者： Balevicius, Robertas Maknickas, Algirdas Sielamowicz, Irena Vilnius Gediminas Tech Univ Dept Reinforced Concrete Struct & Geotech Av Sauletekio 11 LT-10223 Vilnius Lithuania Vilnius Gediminas Tech Univ Inst Mech J Basanaviciaus Str 28 LT-03224 Vilnius Lithuania ISST Ltd St J Matejki 8 PL-15196 Bialystok Poland

Flow analysis of pea grains in a three-dimensional, flat-bottomed bin made of Plexiglas is quantitatively investigated regarding the discharge velocities generated experimentally and those predicted using microand macro mechanical approaches. The discrete-element method is applied to represent the prediction made by the micro mechanical model operating with a dynamic, cohesionless-visco-elastic-frictional contact interaction of spherical grains. The macro-mechanical model is reliant on the purely kinematic continuum-based analytical description of a plug flow. The fixed mean values of the experimentally measured single-grain mechanical properties are introduced in the micro-mechanical model to analyse the reproducibility of the experimentally determined velocity fields as a two-dimensional macro-scale indicators. The Crocker-Grier algorithm based image processing is applied to identify the grains and derive their velocities from the frame data recorded during the bin-discharge tests. The experimental velocities were compared with those computed by the discrete-element and continuum-based kinematical models. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Visco-elastic-frictional contact discrete-element method Discharge velocity fields Image processing Grains tracking

来源：评论

学校读者我要写书评

暂无评论

Simulation of the strain distribution under a two-dimensional sand pile

引用

POWDER TECHNOLOGY 2011年第3期214卷 406-414页

作者： Roul, Pradip Schinner, Alexander Kassner, Klaus Univ Potsdam Inst Appl Math D-14469 Potsdam Germany Univ Magdeburg Inst Theoret Phys D-39106 Magdeburg Germany T Syst D-80995 Munich Germany

We study the averaged macroscopic strain tensor for a sand pile consisting of soft convex polygonal particles numerically, using the discrete-element method (DEM). First, we construct two types of "sand piles" by two different pouring protocols. Afterwards, we deform the sand piles, relaxing them under a 10% reduction of gravity. Four different types of methods, three best-fit strains and a derivative strain, are adopted for determining the strain distribution under a sand pile. The results of four different versions of strains obtained from DEM simulation are compared with each other. Moreover, we compare the vertical normal strain tensor between two types of sand piles qualitatively and show how the construction history of the piles affects their strain distribution. (C) 2011 Elsevier B.V. All rights reserved.

关键词： Numerical simulation Sand pile Stress Strain Granular matter discrete-element method

来源：评论

学校读者我要写书评

暂无评论

The role of self-organization during confined comminution of granular materials

引用

PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES 2010年第1910期368卷 231-247页

作者： Ben-Nun, Oded Einav, Itai Univ Sydney Sch Civil Engn Sydney NSW 2006 Australia

During confined comminution of granular materials a power-law grain size distribution (gsd) frequently evolves. We consider this power law as a hint for fractal topology if self-similar patterns appear across the scales. We demonstrate that this ultimate topology is mostly affected by the rules that define the self-organization of the fragment subunits, which agrees well with observations from simplistic models of cellular automata. There is, however, a major difference that highlights the novelty of the current work: here the conclusion is based on a comprehensive study using two-dimensional 'crushable' discrete-element simulations that do not neglect physical conservation laws. Motivated by the paradigm of self-organized criticality, we further demonstrate that in uniaxial compression the emerging ultimate fractal topology, as given by the fractal dimension, is generally insensitive to alteration of global index properties of initial porosity and initial gsd. Finally, we show that the fractal dimension in the confined crushing systems is approached irrespective of alteration of the criteria that define when particles crush.

关键词： granular materials comminution self-organization discrete-element method compression

来源：评论

学校读者我要写书评

暂无评论

On the role of sphericity of falling rock clusters-insights from experimental and numerical investigations

引用

LANDSLIDES 2018年第2期15卷 219-232页

作者： Gao, Ge Meguid, M. A. McGill Univ Civil Engn & Appl Mech 817 Sherbrooke St W Montreal PQ H3A 0C3 Canada

In this study, the dynamic behavior of rock clusters falling on rough slopes and impacting a vertical barrier is investigated experimentally and numerically using discrete element analysis. A specially designed laboratory setup that involves a flume of adjustable slope lined with a bumpy surface and equipped with an instrumented wall at the toe is used in the experimental investigation. The velocity profiles and impact forces were measured for three inclination angles using two different rock clusters. Three-dimensional discrete element analysis is then conducted to investigate the mechanical behavior of the rockfall and examine the role of sphericity of the rock cluster on the overall behavior of the system. This was achieved by explicitly simulating the complex shapes of the used rocks and the rough surface of the slope. The material coefficient of friction was measured using heap tests, and the results are compared with those obtained numerically using four different particle sphericities. Conclusions are made regarding the effect of slope inclination angle and the volume of the cluster on the impact forces exerted on rigid barriers. This study suggests that rock sphericity plays important roles on the dynamic behavior of the system and should be taken into consideration in simulating rockfall problems.

关键词： Rockfall Impact force Rigid barrier Rock sphericity Dynamic behavior Heap test Coefficient of restitution discrete-element method

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：