检索结果-内蒙古大学图书馆

Simulation of grain growth and sintering process by combined phase-field/discrete-element method

ACTA MATERIALIA 2014年 66卷 360-369页

作者： Shinagawa, Kazunari Kagawa Univ Fac Engn Dept Adv Mat Sci Takamatsu Kagawa 7610396 Japan

A combination of the phase-field method (PFM) and the discrete-element method (DEM) is proposed to simulate simultaneously the movement of particles and the grain growth behavior in powder compacts during sintering. To take the mutual interaction into consideration, a precise way of coupling PFM and DEM is developed based on a sintering model. The sintering forces and the contact areas in linked particles are evaluated from the phase field variables, computed in PFM and introduced into the calculation of the rigid motion of particles in DEM. Before treating actual problems as the application, the sintering process of two particles is simulated first for fundamental verification, including the case with different particle sizes. It is confirmed that the changes in the neck size and the center-to-center distance between particles are reproduced well using the proposed method. Secondly, the simulation of microstructural evolution during sintering is implemented for some small clusters of particles. The internal spatial structure and the outer shape of the clusters vary with the shrinkage deformation as well as the grain boundary migration in sintering. The proposed method of simulating the microstructural evolution in sintering bodies may be effective in the computer-aided design of microscale components or thin films produced by powder processing. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

关键词： Sintering Phase-field method discrete-element method Grain growth Densification

来源：评论

学校读者我要写书评

暂无评论

Coupling of discrete-element method and smoothed particle hydrodynamics for liquid-solid flows

引用

Theoretical & Applied Mechanics Letters 2012年第1期2卷 55-58页

作者： Yrj Jun Huang Ole Jφrgen Nydal Department of Energy and Process Engineering Norwegian University of Science and Technology(NTNU)

Particle based methods can be used for both the simulations of solid and fluid phases in multiphase medium, such as the discrete-element method for solid phase and the smoothed particle hydrodynamics for fluid phase. This paper presents a computational method combining these two methods for solid-liquid medium. The two phases are coupled by using an improved model from a reported Lagrangian-Eulerian method. The technique is verified by simulating liquid-solid flows in a two-dimensional lid-driven cavity.

关键词： discrete-element method smoothed particle hydrodynamics liquid-solid flows lid-driven cavity

来源：评论

学校读者我要写书评

暂无评论

Modeling Geogrid Pullout Behavior in Sand Using discrete-element method and Effect of Tensile Stiffness

引用

INTERNATIONAL JOURNAL OF GEOMECHANICS 2019年第5期19卷

作者： Chen, Wei-Bin Zhou, Wan-Huan Jing, Xue-Ying Univ Macau Dept Civil & Environm Engn Macau 999078 Peoples R China Univ Macau Res Inst Zhuhai 519080 Guangdong Peoples R China Univ Macau State Key Lab Internet Things Smart City Macau 999078 Peoples R China

In this study, a series of numerical pullout tests was performed using the discrete-element method (DEM) to investigate the micromechanical behavior of geogrid pullout and the effect of geogrid tensile stiffness. Geogrid-soil interaction during pullout was investigated not only through displacement fields and force chains inside the soil but also via the quantitative displacement and force distributions along the geogrid. The active and inactive zones were defined based on the displacement fields in the soil, and the displacement corresponding to the boundary between the active and inactive zones was found to be 1.25mm in this study. The higher the geogrid stiffness, the larger was the thickness and length of the active zone mobilized in the soil under the same pullout displacements. The thickness and length for the geogrid with largest tensile stiffness were 150 and 500 mm (full length of geogrid), respectively. Reorientations of contacts and forces within both the inactive and active zones were further visualized based on the Fourier-series approximation. The part of the geogrid that experienced displacement of more than 1.25mm (used for the definition of the active zone) is defined as the affected part, and its corresponding length is defined as the affected length. The stiffer geogrid was found to activate the affected length into the full range more rapidly than the less stiff one prior to failure. The tensile forces at the load ends of stiff geogrids were larger than those at the load ends of extensible geogrids at all given pullout displacements. (C) 2019 American Society of Civil Engineers.

关键词： Soil-structure interaction Geogrid tensile stiffness discrete-element method Pullout behavior

来源：评论

学校读者我要写书评

暂无评论

Effect of Particle Shape on Soil Arching in the Pile-Supported Embankment by 3D discrete-element method Simulation

引用

INTERNATIONAL JOURNAL OF GEOMECHANICS 2022年第4期22卷

作者： Liu, Qi-Wei Chen, Ren-Peng Wang, Han-Lin Yin, Zhen-Yu Wu, Huai-Na Hunan Univ Key Lab Bldg Safety & Energy Efficiency Minist Educ Changsha 410082 Hunan Peoples R China Hunan Univ Natl Ctr Int Res Collaborat Bldg Safety & Environ Changsha 410082 Hunan Peoples R China Hunan Univ Coll Civil Engn Changsha 410082 Hunan Peoples R China Hong Kong Polytech Univ Dept Civil & Environm Engn Kowloon Hung Hom Hong Kong Peoples R China

The particle shape plays an important role in controlling the behavior of granular material, thus needing to be considered in the formation and evolution of soil arching in the pile-supported embankment. Based on the three-dimensional discrete-element method simulation, the effect of the soil particle shape on the formation and evolution of soil arching in the pile-supported embankment is unraveled from the construction to the operation period by adopting spherical, oval, and tetrahedron particles. An additional simulation of spherical particles with the rolling resistance contact model is conducted to reveal the applicability of the indirect method to reproduce the behavior of the case with irregular particles. After sample preparation, four simulation procedures are applied for each case: differential settlement, static loading, cyclic loading, and final equilibrium. The results indicate that due to interlocking, smaller surface settlement occurs for the case with irregular particles at a given simulation state. Furthermore, the case with irregular particles tends to induce a more significant soil arching than the case with spherical particles, also showing a higher resistance to the degradation of soil arching under external load. Owing to various homogeneity and angularity, the two cases with irregular particles present different mechanical patterns under the external load. The reorientation and destruction of the contact force network are the microscale reasons for the formation and degradation of soil arching. As the rolling resistance method cannot fully reproduce the behavior of irregular particles for the soil arching, this method should be carefully validated and used in further simulation of the pile-supported embankment.

关键词： discrete-element method Particle shape Pile-supported embankment Soil arching External load

来源：评论

学校读者我要写书评

暂无评论

Heat Conduction Behaviors in Semiflexible Pavements Using discrete-element method

引用

JOURNAL OF TRANSPORTATION ENGINEERING PART B-PAVEMENTS 2023年第3期149卷

作者： Xu, Jie Yao, Xiaoguang Xu, Tao Nanjing Forestry Univ Coll Civil Engn 159 Longpan Rd Nanjing 210037 Jiangsu Peoples R China

Semiflexible pavement (SFP) includes asphalt mixture skeleton, cement mortar, asphalt mortar, and residual voids. The heat conduction behaviors in the SFP become very complicated. To understand the heat conduction behaviors in the SFP, the discrete element model (DEM) of SFP was first established. Then the heat conduction behaviors, temperature field distribution, and effects of residual pores on heat conduction were investigated. Results indicate that the temperature field distribution at the same pavement depth is relatively uniform, and the heat conduction mainly happens in the vertical direction. The aggregate requires more heat to rise temperature, successively followed by asphalt mortar and cement mortar. The aggregate requires longer heat conduction time, but which does not affect the whole heat transfer. Also, when there are residual pores in the SFP, the temperature at the pore top is higher and the temperature at the pore bottom is lower than that at the same pavement depth without pores due to the thermal resistance of pores, respectively. Furthermore, the larger the pore size is, the higher the temperature difference is. Finally, when the pore is closer to pavement surface, the temperature difference between pore bottom temperature and other temperature at the same pavement depth without pores becomes higher. It is proposed that the large residual pore should be avoided or decreased to reduce the distresses of SFP.

关键词： Semiflexible pavement (SFP) discrete-element method Heat conduction Heat pipe Temperature distribution Residual pore

来源：评论

学校读者我要写书评

暂无评论

Modeling Blast-Induced Fragmentation of Jointed Rock Mass Using Voronoi discrete-element method

引用

INTERNATIONAL JOURNAL OF GEOMECHANICS 2020年第8期20卷

作者： Babanouri, Nima Abdolahpour, Milad Dehghani, Hesam Hamedan Univ Technol Dept Min Engn Hamadan *** Hamadan Iran

Pattern design and management of blasting in open pit mining have been constantly of great interest to many mining engineers so as to reach an appropriate degree of fragmentation for loading, hauling, and crushing systems. Inappropriate fragmentation incurs extra costs in the form of secondary blasting, disruptions in the loading and hauling process, and so forth. To tackle this problem, it is necessary to predict the blast-induced fragmentation. Numerous methods have been proposed by many researchers to predict fragmentation. Regarding technological advancements, and with the advent of numerical codes, the restrictions of empirical methods for the prediction of blast-induced fragmentation can be overcome. The present study developed a model for the estimation of blast-induced fragmentation using a discrete-element method coupled with image processing techniques. In the numerical model, Voronoi elements were used to simulate microcracks of rock materials. Preexisting joints were also present in the model;prior to the blasting, their information was elicited in the area of interest (the Hegmatan limestone mine, Iran). After the blasting, the real fragmentation and modeled fragmentation were compared using image processing software. The results obtained from the numerical modeling were in good agreement with the real data, validating the simulation procedure. Hence, the Voronoi discrete-element method coupled with the image processing technique is appropriately capable of modeling the blasting-induced fragmentation in a discontinuum. Finally, the influence of different parameters, namely delay, presplitting, preexisting joints, discontinuity spacing, and spacing-to-burden ratio, on fragmentation indices were numerically simulated and investigated. The results showed that the lack of delay increases D-50 of fragments from 32.57 to 95.94 cm, the application of presplitting negligibly affects fragmentation, and the preexisting joints in the study area enhanced the fragme

关键词： Rock fragmentation Production blasting discrete-element method Voronoi elements Image processing

来源：评论

学校读者我要写书评

暂无评论

Numerical Simulation of a Single Stone Column in Soft Clay Using the discrete-element method

引用

INTERNATIONAL JOURNAL OF GEOMECHANICS 2018年第12期18卷 04018176-04018176页

作者： Tan, Xin Zhao, Minghua Chen, Wei Hunan Univ Coll Civil Engn Changsha 410082 Hunan Peoples R China Cent S Univ Sch Civil Engn Changsha 410083 Hunan Peoples R China

The coupled discrete-element method-finite difference method (DEM-FDM) numerical modeling scheme was proposed to simulate a single stone column in soft clay according to the Universal Distinct element Code (UDEC). The discrete granular materials that form a stone column can be better simulated by the DEM model, which extends beyond the capability of continuum approaches. In the proposed DEM-FDM coupled numerical model, the stone column was represented by discrete rigid blocks according to the Voronoi tessellation, and the surrounding clay was represented as continuous Mohr-Coulomb material. The settlement, bulging deformation, and failure process involving complicated interactions between the stone column and the surrounding soil were captured well by the proposed numerical model. The accuracy of the proposed model was verified using experimental model test results. The consistency between the numerical simulation and the model test results indicated good potential of the proposed modeling scheme for studying further the load deformation and the failure behaviors of soft ground reinforced by stone columns. The limitations of the proposed numerical model are also discussed in this paper. (C) 2018 American Society of Civil Engineers.

关键词： Stone column Composite foundation discrete-element method Numerical simulation Universal Distinct element Code (UDEC) Bulging

来源：评论

学校读者我要写书评

暂无评论

Construction and parameter calibration of potato double-layer flexible bonding model based on discrete-element method

引用

JOURNAL OF FOOD PROCESS ENGINEERING 2024年第4期47卷

作者： Gai, Xiuzhi Xie, Shengshi Deng, Weigang Lu, Kailiang Ji, Xinjie Inner Mongolia Agr Univ Coll Mech & Elect Engn Hohhot Peoples R China Inner Mongolia Agr Univ Coll Mech & Elect Engn 306 Zhaowuda Rd Hohhot 010018 Peoples R China

The current discrete-element simulation models for potatoes are multisphere polymer models derived from the Hertz-Mindlin (no slip) contact model in the discrete-element simulation software (EDEM). These models oversimplify by considering potato peel and flesh as sharing identical mechanical properties within the structure. This oversimplification impedes a thorough investigation of the characteristics and mechanisms underlying potato peel-breaking damage during mechanized harvesting, making in-depth exploration challenging through simulation experiments. Consequently, this study conducted laboratory tests to determine the water content of potato peel and flesh, as well as the friction coefficients and collision recovery coefficients for various material pairs: flesh-steel, peel-steel, peel-peel, peel-flesh, and flesh-flesh. Subsequently, based on these findings, a double-layer flexible bonding model for potato samples and whole stems under specific water content conditions was developed using EDEM software. The bonding parameters of the double-layer flexible model for potato samples were refined through virtual shear calibration tests, leading to the identification of the optimal parameter combination: Flesh particle-flesh particle normal stiffness(tangential stiffness) per unit area X1 = 4.39 x 108 N/m3, peel particle-flesh particle normal stiffness(shear stiffness) per unit area X3 = 1.81 x 109 N/m3, peel particle-peel particle shear stiffness per unit area X6 = 1.99 x 109 N/m3, peel particle-peel particle critical normal stress X7 = 2.06 x 109 Pa. To validate the accuracy of the bonding parameters, shear and compression validation tests were conducted on entire potato stems. Comparison of the validation results from laboratory tests and simulation tests revealed an average relative error of e = 3.25%, signifying the feasibility of the constructed double-layer flexible bond model for potatoes. This model meets the requirements for studying the characteristics and

关键词： discrete-element method double-layer flexible bonding model EDEM parameter calibration potato

来源：评论

学校读者我要写书评

暂无评论

Numerical discrete-element method Investigation on Failure Process of Recycled Aggregate Concrete

引用

JOURNAL OF MATERIALS IN CIVIL ENGINEERING 2019年第1期31卷

作者： Tan, Xin Li, Wengui Zhao, Minghua Tam, Vivian W. Y. Hunan Univ Coll Civil Engn Changsha 410082 Hunan Peoples R China Univ Technol Sydney Sch Civil & Environm Engn Sydney NSW 2007 Australia Univ Technol Sydney Sch Civil & Environm Engn Ctr Built Infrastruct Res Sydney NSW 2007 Australia Western Sydney Univ Sch Comp Engn & Math Penrith NSW 2751 Australia

This study numerically investigates the failure processes of recycled aggregate concrete (RAC) and natural aggregate concrete (NAC). A two-dimensional simulation based on a discrete-element method (DEM) is conducted with a universal distinct-element code (UDEC) program. RAC is modeled by a combination of rigid Voronoi blocks cemented to each other using contacts for interfaces. The determination procedure of contact microparameters is analyzed, and a series of microscopic contact parameters in different components of modeled recycled aggregate concrete (MRAC) is calibrated using nanoindentation results. The complete stress-strain curves, fracture process, and failure pattern of numerical model are verified by experimental results, proving its accuracy and validation. The initiation, propagation, and coalescence of microcracks and subsequent nonlinear deformation behaviors of cement mortar, modeled natural aggregate, and recycled aggregate concrete are captured through DEM numerical simulations and compared with digital image correlation (DIC) results. It is found that both the new interfacial transition zone and the old interfacial transition zone are the weak links in RAC, where most microcracks initiate and propagate into the cement mortar region. The failure behaviors of MRAC revealed by both experimental and numerical results can effectively provide insights into the failure mechanism and enhancement of RAC.

关键词： discrete-element method Digital image correlation Recycled aggregate concrete (RAC) Compression Crack propagation

来源：评论

学校读者我要写书评

暂无评论

Three-Dimensional discrete-element method Analysis of Stresses and Deformations of a Single Geogrid-Encased Stone Column

引用

INTERNATIONAL JOURNAL OF GEOMECHANICS 2017年第9期17卷 04017070-04017070页

作者： Gu, Meixiang Han, Jie Zhao, Minghua Hunan Univ Coll Civil Engn Changsha 410082 Hunan Peoples R China Univ Kansas Dept Civil Environm & Architectural Engn Lawrence KS 66045 USA

The discrete-element method (DEM) has been successfully used to simulate the behavior of granular material and was used in this study to analyze the stresses and deformations of a single geogrid-encased stone column under unconfined compression. The aggregate was simulated using graded particles of diameters ranging from 30 to 50 mm, and a biaxial geogrid as an encasement material was simulated using parallel-bonded particles. The micromechanical properties of the aggregate were determined using numerical triaxial tests at various confining stresses. The tensile properties of the geogrid were determined by a multirib tensile test, and the flexural rigidity of the geogrid was calibrated by a flexural bending test. This study investigated the changes in vertical and radial stresses and porosities, the contact-force distribution and particle movements within the aggregate, and the deformation and tensile force in the geogrid encasement. The load-displacement response of the DEM model of the geogrid-encased aggregate sample closely agreed with the experimental results. The coefficient of radial stress, defined as the ratio of vertical stress to radial stress within the aggregate, varied from 0.6 to 2.7 during loading where the tensile strength of the geogrid encasement was not fully mobilized. The aggregate showed volumetric contraction at small deformation and then dilation with an increase of deformation. The interlocking effects between the aggregate and the geogrid were observed at the initial state. The particles within the middle portion of the column were more likely to slip than those at other locations. (C) 2017 American Society of Civil Engineers.

关键词： Deformation discrete-element method Encasement Geogrid Stone column Stress

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：