130 results
Search Results
2. A novel scheme for imposing periodic boundary conditions on RVE in second-order computational homogenization for granular material
- Author
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Li, Xikui, Zhang, Songge, and Duan, Qinglin
- Published
- 2019
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3. Compaction effects on permeability of spherical packing
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Zhang, Duzhou, Tian, Zhiguo, Chen, Zhiqiang, Wu, Dengyun, Zhou, Gang, Zhang, Shaohua, and Wang, Moran
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- 2020
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4. Construction of poly-ellipsoidal grain shapes from SMT imaging on sand, and the development of a new DEM contact detection algorithm
- Author
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Zhang, Boning, Regueiro, Richard, Druckrey, Andrew, and Alshibli, Khalid
- Published
- 2018
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5. A coupling method incorporating digital image processing and discrete element method for modeling of geomaterials
- Author
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Meng, Qingxiang, Wang, Huanling, Xu, Weiya, and Zhang, Qiang
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- 2018
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6. Study on the particle stratification and penetration of a swing vibrating screen by using DEM
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Ning, Shuigen, Xiao, Jianzhang, Wang, Guifeng, and Huang, Pengcheng
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- 2020
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7. Establishment and verification of a contact model of flowing fresh concrete
- Author
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Zhao, Yuan, Han, Zhennan, Ma, Yali, and Zhang, Qianqian
- Published
- 2018
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8. Fast computation of accurate sphere-cube intersection volume
- Author
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Jones, Bruce D. and Williams, John R.
- Published
- 2017
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9. Sensitivity analysis of DEM prediction for sliding wear by single iron ore particle
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Chen, Guangming, Schott, Dingena L., and Lodewijks, Gabriel
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- 2017
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10. Correlation of microscopic and macroscopic characteristics of granular materials based on a rolling resistance linear model.
- Author
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Wang, Yiwei, Liu, Run, Sun, Ruohan, and Xu, Zewei
- Subjects
ROLLING friction ,DISCRETE element method ,GRANULAR materials ,ROLLING contact - Abstract
Purpose: The paper aims to find the correlation between the microparameters and the macroparameters of the soil. The study aims to calibrate the macroscale and microscale parameters of rolling resistance contact models to successfully apply the discrete element method to do some research of the geotechnical problem. Design/methodology/approach: The paper opted for an exploratory study using the PFC3D to simulate the triaxial tests that include more than 50 cases and the coupling analysis method, which considering several effect of various factors. Findings: The paper provides a quantitative relationship between the macroparameters and microparameters of the rolling resistance linear model and a method for fast calibration of macroscopic parameters is proposed and verified by a triaxial test example. Originality/value: This paper provides the quantitative relationship of micro and macroparameters in the rolling resistance linear model by studying a single factor and considering the coupling effect of various factors and a fast method for the calibration of microparameters based on the rolling resistance linear model is proposed. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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11. Segmented research and parameter optimization of double-layer vibrating screen.
- Author
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Li, Zhanfu, Liang, Jianbin, Jia, Peiyu, Zheng, Shaoqi, Zhou, Hongzhi, and Tong, Xin
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SHALE shakers ,DISCRETE element method ,FREQUENCIES of oscillating systems ,BINOMIAL distribution - Abstract
Purpose: The purpose of this paper is to study the screen surface parameters of the double deck vibrating screen, in sections, to determine the influence of each part of the screen surface on the screening efficiency of the vibrating screen. Finally, the best screening parameters were calculated to obtain the best screening performance. Design/methodology/approach: In this paper, the discrete element method is used to simulate the process of two-layer subsection screening. Response surface test was used to analyze the influence of various factors and their interactions on screening results. Finally, based on the binomial regression model of screening efficiency, the optimal combination of vibration parameters is calculated. Findings: In the screening process of vibrating screen, due to the different screening environments in each area of the screen surface, the single-layer linear vibrating screen with equal screen surface parameters cannot obtain the best screening performance. Among the single factors, the effect of vibration frequency is the most significant. Originality/value: To address the issue of single layer linear vibrating screens with equal screen surface parameters being unable to maintain optimal screening performance when handling large amounts of materials. This article proposes a double layer vibrating screen with different screen surface grids and screen surface angles to address the problem of low screening performance of traditional single layer linear vibrating screens. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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- View/download PDF
12. DEIM-embedded hybrid snapshot simulation for reduced order model generation.
- Author
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Bai, Feng and Wang, Yi
- Subjects
REDUCED-order models ,HYBRID computer simulation ,DISCRETE element method ,PROPER orthogonal decomposition ,SINGULAR value decomposition - Abstract
Purpose: The purpose of this paper is to establish an intelligent framework to generate the data representatives in snapshot simulation in order to construct the online reduced-order model based on the generated data information. It could greatly reduce the computational time in snapshot simulation and accelerate the computational efficiency in the real-time computation of reduced-order modeling. Design/methodology/approach: The snapshot simulation, which generates the data to construct reduced-order models (ROMs), usually is computationally demanding. In order to accelerate the snapshot generation, this paper presents a discrete element interpolaiton method (DEIM)-embedded hybrid simulation approach, in which the entire snapshot simulation is partitioned into multiple intervals of equal length. One of the three models: the full order model (FOM), local ROM, or local ROM-DEIM which represents a hierarchy of model approximations, fidelities and computational costs, will be adopted in each interval. Findings: The outcome of the proposed snapshot simulation is an efficient ROM-DEIM applicable to various online simulations. Compared with the traditional FOM and the hybrid method without DEIM, the proposed method is able to accelerate the snapshot simulation by 54.4%–63.91% and 10.5%–27.85%, respectively. In the online simulation, ROM-DEIM only takes 4.81%–8.56% of the computational time of FOM, while preserving excellent accuracy (with relative error <1%). Originality/value: 1. A DEIM-embedded hybrid snapshot simulation methodology is proposed to accelerate snapshot data generation and reduced-order model (ROM)-DEIM development. 2. The simulation alternates among FOM, ROM and ROM-DEIM to adaptively generate snapshot data of salient subspace representation while minimizing computational load. 3. The DEIM-embedded hybrid snapshot approach demonstrates excellent accuracy (<1% error) and computational efficiency in both online snapshot simulation and online ROM-DEIM verification simulation. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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13. Simulation of particles screening in pulsating negative pressure shale shaker by coupling CFD and DEM.
- Author
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Yin, Peng, Hou, Yongjun, and Wu, Xianjin
- Subjects
SHALE shakers ,DRILLING fluids ,FLOW separation ,COMPUTATIONAL fluid dynamics ,DISCRETE element method ,DRILLING muds ,GRANULAR flow - Abstract
Purpose: The purpose of this paper is to obtain the combination of working parameters suitable for pulsating negative pressure shale shaker through simulation, which is conducive to efficient recovery of clean drilling fluid and relatively dry cuttings. Design/methodology/approach: Shale shaker is still one of the main equipment in solid–solid and solid–liquid separation processes in drilling industry. This research is based on a new drilling fluids circulation treatment device, namely pulsating negative pressure shale shaker. In this work, a numerical study of particle flow and separation in the pulsating negative pressure shale shaker is carried out by coupling computational fluid dynamics/discrete element method (CFD-DEM). The effect of vibration parameters and negative pressure parameters are studied in terms of conveyance velocity and percent through screen. Findings: The results show that, conveyance velocity of particle is mainly affected by vibration parameters, negative pressure in pulsating form can effectively prevent cuttings from sticking to the screen. Vibration parameters and pulsating airflow velocity peak have great influence on percent through screen, while vibration frequency and screen slope have influence on the time when the percent through screen reaches stability. Originality/value: In this paper, the authors put forward a new kind of drilling waste fluid treatment equipment, and focused on the study of particle movement law. The results have important guiding significance for the selection of structural design parameters and rational use of equipment. In addition, the new device provides a new idea for solid–liquid separation method, which is one of the hot topics in current research. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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14. Numerical simulation study on erosion collapse failure mechanism of cemented conglomerate accumulation.
- Author
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Hu, Chengfu, Shi, Chong, Zhang, Yiping, Chen, Xiao, and Luo, Sha
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EROSION ,CONGLOMERATE ,DISCRETE element method ,HAZARD mitigation ,COMPUTER simulation ,FAILURE mode & effects analysis - Abstract
Purpose: Cemented conglomerate accumulation is a weak and heterogeneous medium that occurs in western China. It consists mainly of argillaceous cement that loses strength rapidly upon contact with water, leading to collapse instability failure. Its deformation failure mechanism is complex and poorly understood. In this paper, the erosion failure mechanism of cemented conglomerate accumulation is investigated. Design/methodology/approach: The collapse failure process after erosion of the slope foot for typical cemented conglomerate accumulation is studied based on field investigation using the particle discrete element method. And how the medium composition, slope angle and cementation degree influence the failure mode and process of the cemented conglomerate accumulation is examined. Findings: The foot erosion of slope induces a tensile failure that typically manifests as "erosion at the foot of slope – tensile cracking at the back edge of slope top – integral collapse." The collapse failure is more likely to occur when the cemented conglomerate accumulation has a higher rock content, a steeper slope angle or a weaker cementation degree. Originality/value: A model based on rigid blocks and disk particles to simulate the cemented conglomerate accumulation is developed. It shows that the hydraulic erosion at the foot of the slope resulted in a different failure mechanism than that of general slopes. The results can inform the stability management, disaster prevention and mitigation of similar slopes. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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15. A model for thin shells in the combined finite-discrete element method.
- Author
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Uzelac, Ivana, Smoljanovic, Hrvoje, Batinic, Milko, Peroš, Bernardin, and Munjiza, Ante
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DISCRETE element method ,NONLINEAR statistical models ,BENCHMARKING (Management) ,DISPLACEMENT (Mechanics) ,FINITE element method - Abstract
Purpose This paper aims to present a new numerical model for geometric nonlinear analysis of thin-shell structures based on a combined finite-discrete element method (FDEM).Design/methodology/approach The model uses rotation-free, three-node triangular finite elements with exact formulation for large rotations, large displacements in conjunction with small strains.Findings The presented numerical results related to behaviour of arbitrary shaped thin shell structures under large rotations and large displacement are in a good agreement with reference solutions.Originality/value This paper presents new computationally efficient numerical model for geometric nonlinear analysis and prediction of the behaviour of thin-shell structures based on combined FDEM. The model is implemented into the open source FDEM package “Yfdem”, and is tested on simple benchmark problems. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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16. Design modification of iron ore bearing transfer chute using discrete element method.
- Author
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Basu, Saprativ, Chakrabarty, Arijit, Nag, Samik, Behera, Kishore, Bandyopadhyay, Brati, Grima, Andrew Phillip, and Ghosh, Probal
- Subjects
DISCRETE element method ,IRON ores ,BULK solids ,FLOW simulations ,WOOD pellets ,COHESIVE strength (Mechanics) ,MATERIALS handling equipment - Abstract
Purpose: The dryer feed chute of the pellet plant plays an important role in the pelletizing process. The chute discharges sticky and moist iron ore fines (<1 mm) to the inline rotary dryer for further processing. Since the inception of the installation of the dryer feed chute, the poor flowability of the feed materials has caused severe problems such as blockages and excessive wear of chute liners. This leads to high maintenance costs and reduced lifetime of the liner materials. Constant housekeeping is needed for maintaining the chute and reliable operation. The purpose of this study is to redesign the dryer feed chute to overcome the above challenges. Design/methodology/approach: The discrete element method (DEM) has been used to model the flow of cohesive materials through the transfer chute. Physical experiments have been performed to understand the most severe flow conditions. A DEM material model is also developed for replicating the worst-case material condition. After identifying the key problem areas, concept designs were proposed and simulated to assess the design improvements to increase the reliability of chute operation. Findings: Flow simulations correlated well with the existing flow behavior of the iron ore fines inside the chute. The location of the problematic areas has been validated with that of the previously installed chute. Subsequently, design modifications have been proposed. This includes modification of deflector plate and change in slope and cross-section of the chute. DEM simulations and analysis were conducted after incorporating these design changes. A comparison in the average velocity of particle and force on chute wall shows a significant improvement using the proposed design. Originality/value: Method to calibrate DEM material model was found to provide accurate prediction and modeling of the flow behavior of bulk material through the real transfer chute. DEM provided greater insight into the performance of the chute especially modeling cohesive materials. DEM is a valuable design tool to assist chute designers troubleshoot and verify chute designs. DEM provides a greater ability to model and assess chute wear. This technique can help in achieving a scientific understanding of the flow properties of bulk solids through transfer chute, hence eliminate challenges, ensuring reliable, uninterrupted and profitable plant operation. This paper strongly advocates the use of calibrated DEM methodology in designing bulk material handling equipment. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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17. Future of the discrete element method in the modelling of grinding wheels.
- Author
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Osa, Juan Luis, Ortega, Naiara, Vidal, Gorka, Fernandez-Gauna, Borja, Carballo, Asier, and Tolosa, Ibon
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DISCRETE element method ,GRINDING wheels ,TOPOGRAPHY ,NUMERICAL analysis ,MATHEMATICAL analysis - Abstract
Purpose The granular structure of a grinding wheel determines its performance remarkably when grinding. Nowadays, grinding wheels are man-made porous conglomerates of hard abrasive grains bonded with a binder. As an engineered material, it would be interesting to foresee the behaviour of the wheel, but it is hindered under its complex heterogeneous nature. Recently, some models based on the discrete element method (DEM) have been presented to model the grinding wheel. This paper aims to identify and propose a framework that must comply with such models and to identify new applications for DEM models in grinding.Design/methodology/approach First, the characteristics of the grinding wheel are described. In this way, the framework of DEM models of a grinding wheel material is developed, reproducing both the granular morphology and stiffness.Findings The paper asserts a promising future that provides the DEM in the modelling of grinding.Originality/value The potential of DEM in grinding is analysed, proposing new applications. It can be used as topography model, which can also model the stiffness. In addition, DEM opens a new interesting research line: the modelling of the grit breakout. It draws up the development of essential dressing and wear models. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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18. Comparison between O(n2) and O(n) neighbor search algorithm and its influence on superlinear speedup in parallel discrete element method (DEM) for complex-shaped particles.
- Author
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Yan, Beichuan and Regueiro, Richard
- Subjects
SEARCH algorithms ,DISCRETE element method ,SUPERCOMPUTERS ,COMPUTATIONAL mathematics ,ENGINEERING - Abstract
Purpose This paper aims to present performance comparison between O(n
2 ) and O(n) neighbor search algorithms, studies their effects for different particle shape complexity and computational granularity (CG) and investigates the influence on superlinear speedup of 3D discrete element method (DEM) for complex-shaped particles. In particular, it aims to answer the question: O(n2 ) or O(n) neighbor search algorithm, which performs better in parallel 3D DEM computational practice?Design/methodology/approach The O(n2 ) and O(n) neighbor search algorithms are carefully implemented in the code paraEllip3d, which is executed on the Department of Defense supercomputers across five orders of magnitude of simulation scale (2,500; 12,000; 150,000; 1 million and 10 million particles) to evaluate and compare the performance, using both strong and weak scaling measurements.Findings The more complex the particle shapes (from sphere to ellipsoid to poly-ellipsoid), the smaller the neighbor search fraction (NSF); and the lower is the CG, the smaller is the NSF. In both serial and parallel computing of complex-shaped 3D DEM, the O(n2 ) algorithm is inefficient at coarse CG; however, it executes faster than O(n) algorithm at fine CGs that are mostly used in computational practice to achieve the best performance. This means that O(n2 ) algorithm outperforms O(n) in parallel 3D DEM generally.Practical implications Taking for granted that O(n) outperforms O(n2 ) unconditionally, complex-shaped 3D DEM is a misconception commonly encountered in the computational engineering and science literature.Originality/value The paper clarifies that performance of O(n2 ) and O(n) neighbor search algorithms for complex-shaped 3D DEM is affected by particle shape complexity and CG. In particular, the O(n2 ) algorithm outperforms the O(n) algorithm in large-scale parallel 3D DEM simulations generally, even though this outperformance is counterintuitive. [ABSTRACT FROM AUTHOR]- Published
- 2018
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- View/download PDF
19. Overlapped-coupling between spherical discrete elements and micropolar finite elements in one dimension using a bridging-scale decomposition for statics.
- Author
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Regueiro, Richard, Duan, Zheng, and Yan, Beichuan
- Subjects
GRANULAR materials ,DISCRETE element method ,FINITE element method ,MATHEMATICAL decomposition ,COMPUTATIONAL physics - Abstract
Purpose – The purpose of this paper is to develop a concurrent multiscale computational method for granular materials in the quasi-static loading regime. Design/methodology/approach – Overlapped-coupling between a micropolar linear elastic one-dimensional (1D) mixed finite element (FE) model and a 1D chain of Hertzian nonlinear elastic, glued, discrete element (DE) spheres is presented. The 1D micropolar FEs and 1D chain of DEs are coupled using a bridging-scale decomposition for static analysis. Findings – It was found that an open-window DE domain may be coupled to a micropolar continuum FE domain via an overlapping region within the bridging-scale decomposition formulation for statics. Allowing the micropolar continuum FE energy in the overlapping region to contribute to the DE energy has a smoothing effect on the DE response, especially for the rotational degrees of freedom (dofs). Research limitations/implications – The paper focusses on 1D examples, with elastic, glued, DE spheres, and a linear elastic micropolar continuum implemented in 1D. Practical implications – A concurrent computational multiscale method for granular materials with open-window DE resolution of the large shearing region such as at the interface with a penetrometer skin, will allow more efficient computations by reducing the more costly DE domain calculations, but not at the expense of generating artificial boundary effects between the DE and FE domains. Originality/value – Open-window DE overlapped-coupling to FE continuum domain, accounting for rotational dofs in both DE and FE methods. Contribution of energy from micropolar FE in overlap region to underlying DE particle energy. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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20. Effects of density ratio and diameter ratio on penetration of rotation projectile obliquely impacting a granular medium.
- Author
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Ye, Xiaoyan, Wang, Dengming, and Zheng, Xiaojing
- Subjects
DENSITY ,DENSITOMETERS ,GRANULAR materials ,DISCRETE element method ,ANGULAR measurements - Abstract
Purpose – Granular material exhibits rich dynamical behaviors under impacting, and its impacting dynamical process is seriously influenced by many factors. The purpose of this paper is to explore the dynamical response of granular bed obliquely impacted by a rotational projectile, and the effect of density ratio and diameter ratio on its penetration depth is mainly considered. Design/methodology/approach – In most experiments, as the angular velocity and the impact velocity always produce a coupling effect on the whole impact process, then it is quite difficult to separately distinguish the influence of angular velocity. Therefore, the discrete element method is used here to achieve this purpose. The authors vary one parameter and keep other parameter unchanged, and then discuss the effect of these parameters on penetration depth statistically. Findings – The numerical model in this paper can effectively predict the dynamical process of granular medium under impacting. The projectile’s penetration depth exhibits a similar scaling with its angular velocity under different density ratios and diameter ratios, and the angular velocity exhibits an obvious criticality. Originality/value – A DEM code and corresponding statistical approach are used to explore the complex dynamical process of a granular material obliquely impacted by a rotation projectile. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
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21. A yield function for granular materials based on microstructures.
- Author
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Liu, Sihong, Wang, Zijian, Wang, Yishu, Wang, Liujiang, and Fu, Zhongzhi
- Subjects
GRANULAR materials ,COMPUTER simulation ,DISCRETE element method ,ENGINEERING design - Abstract
Purpose – The purpose of this paper is to propose a new yield function for granular materials based on microstructures. Design/methodology/approach – A biaxial compression test on granular materials under different stress paths is numerically simulated by distinct element method. A microstructure parameter S that considers both the arrangement of granular particles and the inter-particle contact forces is proposed. The evolution of the microstructure parameter S under the simulated stress paths is analyzed, from which a yield function for granular materials is derived. The way of determining the two parameters involved in the yield function is proposed. Findings – The new yield function is calibrated using the test data of one sand and two rockfill materials. The shape of the new yield surface is similar to that of the Cam-clay model. Originality/value – The paper proposes a microstructure parameter S, which considers both the arrangement of granular particles and the inter-particle contact forces. From the evolution of S, a yield function for granular materials is derived. The proposed yield function has a simple structure and the parameters are easy to be determined, leading to a feasible realization of engineering application. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
22. DEM analyses of shear band in granular materials.
- Author
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Jiang, Mingjing and Zhang, Wangcheng
- Subjects
DISCRETE element method ,GRANULAR materials ,SHEAR (Mechanics) ,MICROELECTROMECHANICAL systems ,ENERGY dissipation - Abstract
Purpose – Shear-induced strain localization in granular materials has been a hot topic under intensive research during the last four decades. However, the micromechanical process and mechanisms underlying the initiation and development of shear bands are still not fully understood. The purpose of this paper is to eliminate this deficiency. Design/methodology/approach – The paper carries out several two-dimensional distinct element method simulations to examine various global and local micromechanical quantities particular the energy dissipation and local stress and strain invariants with a special emphasis on the initiation and propagation of shear bands. Moreover, the effects of various influential variables including initial void ratio, confining stress, inter-particle friction coefficient, rolling resistance coefficient, specimen slenderness and strain rate on the pattern, scope and degree of shear bands are investigated. Findings – Novel findings of the relationship between sliding and rolling dissipation band and shear band are achieved, indicating a plastic dissipation nature for the shear band. The high inter-particle sliding or rolling resistance, relative small initial void ratio, relative low confining stress and high strain rate facilitate the formation of shear band. In addition, the specimen slenderness affects the pattern of shear band. Originality/value – In this paper, a comprehensive and deep investigation on shear band formation linked with localization of energy dissipation and strain invariants was presented. The new findings on particle scale during shear band formation helps to develop robust micromechanics-based constitutive models in the future. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
23. Soft impact responses of laminated glass simulated with the combined finite-discrete element method.
- Author
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Chen, Xudong and Chan, Andrew
- Subjects
DISCRETE element method ,LAMINATED glass ,FRACTURE mechanics ,DEFORMATIONS (Mechanics) ,CONTINUUM damage mechanics - Abstract
Purpose This paper aims to investigate the responses of laminated glass under soft body impact, including elastic impact and fracture/fragmentation consideration.Design/methodology/approach The simulation uses the combined finite-discrete element method (FDEM) which combines finite element mesh into discrete elements, enabling the accurate prediction of contact force and deformation. Material rupture is modelled with a cohesive fracture criterion, evaluating the process from continua to discontinua.Findings Responses of laminated glass under soft impact (both elastic and fracture) agree well with known data. Crack initiation time in laminated glass increases with the increase of the outside glass thickness. With the increase of Eprojectile, failure mode is changing from flexural to shear, and damage tends to propagate longitudinally when the contact surface increases. Results show that the FDEM is capable of modelling soft impact behaviour of laminated glass successfully.Research limitations/implications The work is done in 2D, and it will not represent fully the 3D mechanisms.Originality/value Elastic and fracture behaviour of laminated glass under soft impact is simulated using the 2D FDEM. Limited work has been done on soft impact of laminated glass with FDEM, and special research endeavours are warranted. Benchmark examples and discussions are provided for future research. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
24. In-plane dynamic response of a hydraulic pipe subjected to random vibration.
- Author
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Qu, Wei, Zhang, Huailiang, Li, Wei, Peng, Ling, and Sun, Wenqian
- Subjects
RANDOM vibration ,HAMILTON'S principle function ,EQUATIONS of motion ,DISCRETE element method ,FLUID-structure interaction ,PIPE ,BALLAST (Railroads) - Abstract
Purpose: To improve the transmission efficiency and reduce the damage to pipes in the hydraulic systems of tunnel boring machine subjected to random vibration, this paper aims to propose a novel dynamic characteristic analysis method that considers random vibration. Design/methodology/approach: A fluid-structure interaction motion equation of the pipe is established by using Hamilton's principle. The finite element method and discrete analysis method of random vibration are used to construct a model of the dynamic behavior of the pipe. Findings: The influences of fluid parameters and external excitation parameters on the dynamic characteristics of pipes are analyzed. The experimental results are found to be in good agreement with the simulation results, which demonstrates that the proposed analytical method can provide a theoretical reference for the design and selection of hydraulic pipes subjected to random vibration. Originality/value: The proposed method can be regarded as a future calculation method for pipes subjected to random vibration, and the transmission efficiency of the pipe can be improved. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
25. Structure optimization of plough blades in a ploughshare mixer using the DEM simulations.
- Author
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Fang, Ziqiang, Peng, Songlin, Yi, Jiangang, and Du, Jun
- Subjects
DISCRETE element method ,PLOWS - Abstract
Purpose: The purpose of this paper is to optimize the structure of plough blades in a ploughshare mixer using the discrete element method (DEM) simulations. Design/methodology/approach: Using the validated DEM model, three numerical tests are conducted to determine how the mixing performance evolves as structural parameters of blades change. Results from the analysis provide basis for structure optimization of blades. The structural parameters include sweep angle of blade γ, regular axial pitch p and regular circumferential angular offset α. The parameters to evaluate mixing performance include mass flow rate and Lacey index. Findings: The DEM results show that the mixing performance at γ of 35° is better than 15°, 25° and 45°. The mixer which has a p of less than or equal to 1.11 · b is more efficient than the mixer which has a p greater than 1.11 · b, where b is tail width of blade. The circumferential symmetric distribution of blades (α = 180°) is more beneficial to improve the mixing performance in comparison with the circumferential asymmetric distribution (α < 180°). Based on the results, an optimized mixer with a γ of 35°, a p of 0.61 · b and an α of 180° is proposed, which has a better mixing performance compared to all mixers listed. Originality/value: The structural parameters of blades, including γ, p and α, are found to be critical for good mixing. From the view angle of structure optimization of plough blades, a new ploughshare mixer with a γ of 35°, a p of 0.61 · b and an α of 180° is investigated and recommended for improving mixing efficiency. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
26. Numerical comparison of some contact detection algorithms.
- Author
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Schiava D'Albano, Guillermo Gonzalo, Lukas, Tomas, Su, Fang, Korakianitis, Theodosios, and Munjiza, Ante
- Subjects
COMPUTER simulation ,DISCRETE element method ,COMPUTER algorithms ,NUMERICAL analysis ,MOLECULAR dynamics - Abstract
Purpose Contact interaction and contact detection (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. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
27. Simulation of fines migration using a non-Newtonian lattice Boltzmann-discrete element modelPart II: 3D extension and applications.
- Author
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Leonardi, C.R., Owen, D.R.J., and Feng, Y.T.
- Subjects
SIMULATION methods & models ,LATTICE theory ,BOLTZMANN'S equation ,ABSTRACT algebra ,TRANSPORT theory - Abstract
Purpose |!|#8211; The purpose of this paper is to present a novel computational framework based on the lattice Boltzmann method (LBM) and discrete element method (DEM) capable of simulating fines migration in three dimensions. Fines migration occurs in a block cave mine, and is characterised by the faster movement of fine and often low-grade material towards the draw point in comparison to larger, blocky material. Design/methodology/approach |!|#8211; This study builds on the foundations and applications outlined in a companion paper, in which the non-Newtonian LBM-DEM framework is defined and applied in 2D simulations. Issues relevant to the extension to 3D, such as spatial discretisation, fluid boundary conditions and the definition of synthetic bulk material parameters using a power law model, are discussed. Findings |!|#8211; The results of the 3D DEM percolation replication showed that migration is predominantly limited to within the draw zone, and that the use of a low-cohesion material model resulted in a greater amount of fines migration. The draw sensitivity investigation undertaken with the two bell partial block cave analysis did not show a significant difference in the amount of migration, despite the two draw strategies being deliberately chosen to result in isolated and interactive draw of material. Originality/value |!|#8211; Along with the companion paper, this paper presents a novel application of the developed non-Newtonian LBM-DEM framework in the investigation of fines migration, which until now has been limited to scale models, cellular automata or pure DEM simulations. The results highlight the potential for this approach to be applied in an industrial context, and indicate a number of potential avenues for further research. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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28. On Minkowski difference-based contact detection in discrete/discontinuous modelling of convex polygons/polyhedra: Algorithms and implementation.
- Author
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Feng, Y.T. and Tan, Yuanqiang
- Subjects
POLYHEDRA ,POLYGONS ,DISCRETE element method ,ALGORITHMS ,ENERGY conservation - Abstract
Purpose: Contact detection for convex polygons/polyhedra has been a critical issue in discrete/discontinuous modelling, such as the discrete element method (DEM) and the discontinuous deformation analysis (DDA). The recently developed 3D contact theory for polyhedra in DDA depends on the so-called entrance block of two polyhedra and reduces the contact to evaluate the distance between the reference point to the corresponding entrance block, but effective implementation is still lacking. Design/methodology/approach: In this paper, the equivalence of the entrance block and the Minkowski difference of two polyhedra is emphasised and two well-known Minkowski difference-based contact detection and overlap computation algorithms, GJK and expanding polytope algorithm (EPA), are chosen as the possible numerical approaches to the 3D contact theory for DDA, and also as alternatives for computing polyhedral contact features in DEM. The key algorithmic issues are outlined and their important features are highlighted. Findings: Numerical examples indicate that the average number of updates required in GJK for polyhedral contact is around 6, and only 1 or 2 iterations are needed in EPA to find the overlap and all the relevant contact features when the overlap between polyhedra is small. Originality/value: The equivalence of the entrance block in DDA and the Minkowski difference of two polyhedra is emphasised; GJK- and EPA-based contact algorithms are applied to convex polyhedra in DEM; energy conservation is guaranteed for the contact theory used; and numerical results demonstrate the effectiveness of the proposed methodologies. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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- View/download PDF
29. A velocity corrected unresolved CFD-DEM coupled method to reproduce wake effects at moderate Reynolds number.
- Author
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Wang, Zekun, Walayat, Khuram, and Liu, Moubin
- Subjects
GRANULAR flow ,FINITE volume method ,DISCRETE element method ,RELATIVE velocity ,CLUSTERING of particles - Abstract
Purpose: The purpose of this paper is to develop a corrected unresolved CFD-DEM method that can reproduce the wake effects in modeling particulate flows at moderate Reynolds number. Design/methodology/approach: First, the velocity field in the wake behind a settling particle is numerically investigated by a resolved method, in which the finite volume method (FVM) is applied to model the fluid flow, discrete element method (DEM) is applied to simulate the motion of particles and immersed boundary method (IBM) is used to tackle fluid solid interaction. Second, an analytical scaling law is given, which can effectively describe the velocity field in the wake behind the settling particle at low and middle Reynolds numbers. Third, this analytical expression is incorporated into unresolved modeling to correct the relative velocity between the particle and its surrounding fluid and enable the influence of the wake of the particle on its neighboring particles. Findings: Two numerical examples, the sedimentation of dual particles, a list of particles and even more particles are provided to show the effectiveness of the presented velocity corrected unresolved method (VCUM). It is found that, in both examples simulated with VCUM, the relative positions of the particles changed, and drafting & kissing phenomenon and particle clustering phenomenon were clearly observed. Practical implications: The developed VCUM can be highly beneficial for modeling industrial particulate flows with DKT and particle clustering phenomena. Originality/value: VCUM innovatively incorporates the wake effects into unresolved CFD-DEM method. It improves the computational accuracy of conventional unresolved methods with comparable results from resolved modeling, while the computational cost is greatly reduced. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
30. DEM modeling of cantilever retaining excavations.
- Author
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Jiang, Mingjing, Shen, Zhifu, and Utili, Stefano
- Subjects
CANTILEVERS ,MATHEMATICAL models ,EXCAVATION ,LUNAR exploration ,LUNAR geology ,LUNAR gravitational effects ,LUNAR gravity - Abstract
Purpose – Retained excavation is important for future lunar exploratory missions and potential human colonization that requires the construction of permanent outposts. Knowledge in excavation obtained on the earth is not directly applicable to lunar excavation because of the low lunar gravity and the non-negligible adhesive van der Waals interactions between lunar regolith grains. The purpose of this paper is to reveal how the gravity level and lunar environment conditions should be considered to extend the knowledge in earth excavation response to lunar excavation. Design/methodology/approach – Two-dimensional discrete element method simulations were carried out to investigate the respective effect of gravity level and lunar environment conditions (high-vacuum and extreme temperature) on retained excavation response. A novel contact model was employed with a moment – relative rotation law to account for the angularity of lunar soil particles, and a normal attractive force to account for the van der Waals interactions. Findings – The simulation results showed that the excavation response is non-linearly related to the gravity level. Van der Waals interactions can increase the dilatancy of lunar regolith and, surprisingly as a consequence, significantly increase the bending moment and deflection of the retaining wall, and the ground displacements. Based on the simulation results, a parabola model was proposed to predict the excavation-induced lateral ground movements on the moon. Originality/value – This study indicates that an unsafe estimate of the wall response to an excavation on the moon would be obtained if only the effect of gravity is considered while the effect of van der Waals interactions is neglected. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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- View/download PDF
31. Investigation of the effect of different gravity conditions on penetration mechanisms by the Distinct Element Method.
- Author
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Jiang, Mingjing, Liu, Fang, Wang, Huaning, and Wang, Xinxin
- Subjects
PHYSIOLOGICAL effects of gravity ,PENETRATION mechanics ,DISCRETE element method ,CENTRIFUGES ,CONE penetration tests - Abstract
Purpose – The purpose of this paper is to present an investigation of the effect of different gravity conditions on the penetration mechanism using the two-dimensional Distinct Element Method (DEM), which ranges from high gravity used in centrifuge model tests to low gravity incurred by serial parabolic flight, with the aim of efficiently analyzing cone penetration tests on the lunar surface. Design/methodology/approach – Seven penetration tests were numerically simulated on loose granular ground under different gravity conditions, i.e. one-sixth, one-half, one, five, ten, 15 and 20 terrestrial gravities. The effect of gravity on the mechanisms is examined with aspect to the tip resistance, deformation pattern, displacement paths, stress fields, stress paths, strain and rotation paths, and velocity fields during the penetration process. Findings – First, under both low and high gravities, the penetration leads to high gradients of the value and direction of stresses in addition to high gradients in the velocity field near the penetrometer. In addition, the soil near the penetrometer undergoes large rotations of the principal stresses. Second, high gravity leads to a larger rotation of principal stresses and more downward particle motions than low gravity. Third, the tip resistance increases with penetration depth and gravity. Both the maximum (steady) normalized cone tip resistance and the maximum normalized mean (deviatoric) stress can be uniquely expressed by a linear equation in terms of the reciprocal of gravity. Originality/value – This study investigates the effect of different gravity conditions on penetration mechanisms by using DEM. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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- View/download PDF
32. Modelling of ice rubble in the punch shear tests with cohesive 3D discrete element method.
- Author
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Sorsimo, Arto and Heinonen, Jaakko
- Subjects
SHEAR testing of soils ,DISCRETE element method ,LINEAR systems ,PARAMETER estimation ,NUMERICAL analysis - Abstract
Purpose This paper aims to simulate a punch shear test of partly consolidated ice ridge keel by using a three-dimensional discrete element method. The authors model the contact forces between discrete ice blocks with Hertz–Mindlin contact model. For freeze bonds between the ice blocks, the authors apply classical linear cohesion model with few modifications. Based on punch shear test simulations, the authors are able to determine the main characteristics of an ice ridge from the material parameters of the ice and freeze bonds.Design/methodology/approach The authors introduced a discrete model for ice that can be used for modelling of ice ridges. The authors started with short introduction to current status with ice ridge modelling. Then they introduced the model, which comprises Hertz–Mindlin contact model and freeze bond model with linear cohesion and softening. Finally, the authors presented the numerical results obtained using EDEM is commercial Discrete Element Modeling software (EDEM) and analysed the results.Findings The Hertz–Mindlin model with cohesive freeze bonds and linear softening is a reasonable model for ice rubble. It is trivial that the ice blocks within the ice ridge are not spherical particles, but according to results, the representation of ice blocks as spheres gave promising results. The simulation results provide information on how the properties of freeze bond affect the results of punch shear test. Thus, the simulation results can be used to approximate the freeze bonds properties within an ice ridge when experimental data are available.Research limitations/implications As the exact properties of ice rubble are unknown, more research is required both in experimental and theoretical fields of ice rubble mechanics.Originality/value Based on this numerical study, the authors are able to determine the main characteristics of an ice ridge from material parameters of ice and freeze bonds. Furthermore, the authors conclude that the model creates a promising basis for further development in other applications within ice mechanics. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
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33. Discrete element modeling of vibrating tillage tools.
- Author
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Keppler, Istvan, Hudoba, Zoltan, Oldal, Istvan, Csatar, Attila, and Fenyvesi, Laszlo
- Subjects
TILLAGE ,MACHINERY vibration ,DISCRETE element method ,CULTIVATORS ,AGRICULTURAL equipment ,ENERGY measurement ,GRANULAR materials ,EQUIPMENT & supplies - Abstract
Purpose - The analysis of the effect of tool vibrations on the measured and simulated draught forces of cultivator tools. This paper aims to discuss this issue. Design/methodology/approach - Soil bin measurements and discrete element method (DEM)-based simulations. Findings - The soil-tool interaction induced free vibrations of cultivator tools have significant impact on the measured draught force, and the simulations made by using vibrating tools give similar results. Research limitations/implications - Accurate calibration of discrete element model parameters can be done based on the reproduction of the whole Mohr-Coulomb failure line. Draught force ratio - velocity ratio values seem to be independent of tool geometry and soil conditions in case of velocity ratio higher than 2. Practical implications - DEM-based numerical simulations can be used for modeling the effect of tool vibration on the draught force values. During discrete element simulations of soil-tool interaction, the effect of tool vibration may not be neglected. Originality/value - The paper demonstrates that during the discrete element modelling of the soil-tool interaction, the tool vibration phenomenon should not be neglected. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
34. Adaptive discrete-continuous modeling of evolving discontinuities.
- Author
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Sorg, Annika and Bischoff, Manfred
- Subjects
CONTINUUM mechanics ,MICROSTRUCTURE ,FINITE element method ,DISCRETE element method ,COMPUTATIONAL mechanics ,MATHEMATICAL models - Abstract
Purpose – The purpose of this paper is to develop a method to model entire structures on a large scale, at the same time taking into account localized non-linear phenomena of the discrete microstructure of cohesive-frictional materials. Design/methodology/approach – Finite element (FEM) based continuum methods are generally considered appropriate as long as solutions are smooth. However, when discontinuities like cracks and fragmentation appear and evolve, application of models that take into account (evolving) microstructures may be advantageous. One popular model to simulate behavior of cohesive-frictional materials is the discrete element method (DEM). However, even if the microscale is close to the macroscale, DEMs are computationally expensive and can only be applied to relatively small specimen sizes and time intervals. Hence, a method is desirable that combines efficiency of FEM with accuracy of DEM by adaptively switching from the continuous to the discrete model where necessary. Findings – An existing method which allows smooth transition between discrete and continuous models is the quasicontinuum method, developed in the field of atomistic simulations. It is taken as a starting point and its concepts are extended to applications in structural mechanics in this paper. The kinematics in the method presented herein is obtained from FEM whereas DEM yields the constitutive behavior. With respect to the constitutive law, three levels of resolution – continuous, intermediate and discrete – are introduced. Originality/value – The overall concept combines model adaptation with adaptive mesh refinement with the aim to obtain a most efficient and accurate solution. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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- View/download PDF
35. Particle crushing simulations with improved discontinuous deformation analysis.
- Author
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Wang, Xiao-Bo, Xu, Wen-Jie, Zhang, Bing-Yin, and Sun, Qi-Cheng
- Subjects
EARTH dams ,COMPUTER simulation of deformations ,PARTICLE interactions ,ELLIPSOIDS ,STRUCTURAL analysis (Engineering) ,DISCRETE element method ,MATHEMATICAL models - Abstract
Purpose – Rock-fill dams are embankments of compacted free-draining granular earth containing an impervious zone. Earth utilized in such dams often contains a high percentage of large particles – hence the term rock-fill. Mass stability of these dams results from friction and particle interactions rather than through a cementing agent binding the particles together. However, high-stress conditions and prolonged exposure to the elements can severely damage rock-fill. Therefore, understanding and modeling rock-fill breakage is important for dam engineering. The purpose of this paper is to improve discontinuous deformation analysis (DDA) techniques for modeling rock-fill breakage, proving the new method using simulations of spherical particle crushing. Design/methodology/approach – This work models rock-fill as bonded ellipsoid particles, and develops an improved DDA method to model the breakage of particle assemblies. The paper starts by describing the principles of three-dimensional DDA for spherical particles, and then derives the submatrices for normal contact, shear contact, and frictional force. The new algorithm incorporates a bond model with a revised open-close iteration algorithm into the DDA method to simulate particle crushing. To validate the improved DDA method, calculated particle contacts and movements are validated against theoretical results. Finally, this work performs a series of point-loading experimental tests for cement ellipsoid particles of both high and low compression strengths, with the test results compared against the results from corresponding DDA simulations. Findings – In particle crushing tests, the force and displacement show an approximately linear relationship until the crushing point, at which point low compression ellipsoid particles split into several large pieces while the high-compression particles break into many small fragments. The DDA simulation results are in good agreement with the crushing tests, demonstrating the validity of the DDA method for solving particle crushing problems. Although the improved DDA model is applicable to rock-fill particle crushing studies, some issues remain, particularly in increasing calculation efficiency and performing large-scale computations and long real-time simulations. Future research should address these issues. Originality/value – A bond model with a revised open-close iteration algorithm is incorporated into the DDA method. The simulated results shed insight into rock-fill crushing mechanisms, an element of concern in engineering practices. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
36. Discrete element method simulation and experimental validation of particle damper system.
- Author
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Lu, Zheng, Lu, Xilin, Jiang, Huanjun, and Masri, Sami F.
- Subjects
DAMPERS (Mechanical devices) ,MOTION control devices ,PARTICLES ,DISCRETE element method ,ALGORITHMS ,VISCOELASTIC materials - Abstract
Purpose – The particle damper is an efficient vibration control device and is widely used in engineering projects; however, the performance of such a system is very complicated and highly nonlinear. The purpose of this paper is to accurately simulate the particle damper system properly, and help to understand the underlying physical mechanics. Design/methodology/approach – A high-fidelity simulation process is well established to account for all significant interactions among the particles and with the host structure system, including sliding friction, gravitational forces, and oblique impacts, based on the modified discrete element method. In this process, a suitable particle damper system is modeled, reaction forces between particle aggregates and the primary structure are incorporated, a reasonable contact force model and time step are determined, and an efficient contact detection algorithm is adopted. Findings – The numerical results are further validated by both special computational tests and shaking table tests, with good agreements to the experimental results. The method is shown to be effective and accurate to simulate the particle damper system. Originality/value – The approaches described in this paper provide an efficient numerical way to investigate complex particle damper systems. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
37. Polyhedra faster than spheres?
- Author
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Hopkins, Mark A.
- Subjects
DISCRETE element method ,POLYHEDRA ,SPHERES ,ENGINEERING simulations ,ELLIPSOIDS - Abstract
Purpose – The purpose of this paper is to present a new and efficient technique for discrete element modelling using non-convex polyhedral grain shapes. Design/methodology/approach – The efficiency of the technique follows from the use of grains that are dilated versions of the basic polyhedral grain shapes. Dilation of an arbitrary polyhedral grain is accomplished by placing the center of a sphere of fixed radius at every point on the surface. The dilated vertices become sphere segments and the edges become cylinder segments. The sharpness of the vertices and edges can be adjusted by varying the dilation radius. Contacts between two dilated polyhedral grains can be grouped into three categories; vertex on surface, vertex on edge, and edge on edge, or in the grammar of the model, sphere on polygonal surface, sphere on cylinder, and cylinder on cylinder. Simple, closed-form solutions exist for each of these cases. Findings – The speed of the proposed polyhedral discrete element model is compared to similar models using spherical and ellipsoidal grains. The polyhedral code is found to run about 40 percent as fast as an equivalent code using spherical grains and about 80 percent as fast as an equivalent code using ellipsoidal grains. Finally, several applications of the polyhedral model are illustrated. Originality/value – Few examples of discrete element modeling studies in the literature use polyhedral grains. This dearth is because of the perceived complexity of the polyhedral coding challenges and the slow speed of the codes compared to codes for other grain shapes. This paper presents a much simpler approach to discrete element modeling using polyhedral grain shapes. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
38. The influence of particle shape on screening: case studies regarding DEM simulations.
- Author
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Wang, Xiaoyue, Li, Zhanfu, Tong, Xin, and Ge, Xiaole
- Subjects
DISCRETE element method ,PARTICLES ,COMPUTER simulation ,VIBRATION (Mechanics) ,ANGLES - Abstract
Purpose The purpose of this study is to explore how particle shape influences the screening, including screening efficiency per unit time, and the relationship between vibration parameters and screening efficiency per unit time in discrete element method (DEM) numerical simulations.Design/methodology/approach In this paper, a three-dimensional discrete element model of vibrating screen with composite vibration form of swing and translation was proposed to simulate the screening process. In total, 11 kinds of non-spherical particles whose shapes changed in a continuous regularity gradual process were established using a multi-sphere method. In the DEM simulations, vibration parameters, including vibration frequency, vibration amplitude and stroke angle, and swing parameters, including swing frequency and swing angle, were changed to perform parametric studies.Findings It shows that the effect of particle shape on screening efficiency is quantitative actually. However, the trends of different shape particles’ screening efficiency per unit time are mainly consistent.Originality/value Some simple particle shapes can be expected to be explored to do screening simulation studies reasonably with modification of the simulation data in DEM numerical simulations. That may improve the computational efficiency of numerical simulations and provide guidance to the study of the screening process. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
39. Co-simulation framework of discrete element method and multibody dynamics models.
- Author
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Lommen, Stef, Lodewijks, Gabriel, and Schott, Dingena L.
- Subjects
DISCRETE element method ,MATERIALS handling equipment ,MULTIBODY systems ,ROBUST control ,STABILITY (Mechanics) - Abstract
Purpose Bulk material-handling equipment development can be accelerated and is less expensive when testing of virtual prototypes can be adopted. However, often the complexity of the interaction between particulate material and handling equipment cannot be handled by a single computational solver. This paper aims to establish a framework for the development, verification and application of a co-simulation of discrete element method (DEM) and multibody dynamics (MBD).Design/methodology/approach The two methods have been coupled in two directions, which consists of coupling the load data on the geometry from DEM to MBD and the position data from MBD to DEM. The coupling has been validated thoroughly in several scenarios, and the stability and robustness have been investigated.Findings All tests clearly demonstrated that the co-simulation is successful in predicting particle–equipment interaction. Examples are provided describing the effects of a coupling that is too tight, as well as a coupling that is too loose. A guideline has been developed for achieving stable and efficient co-simulations.Originality/value This framework shows how to achieve realistic co-simulations of particulate material and equipment interaction of a dynamic nature. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
40. Large-scale dynamic and static simulations of complex-shaped granular materials using parallel three-dimensional discrete element method (DEM) on DoD supercomputers.
- Author
-
Yan, Beichuan and Regueiro, Richard
- Subjects
GRANULAR materials ,PARTICLE analysis ,DISCRETE element method ,SUPERCOMPUTERS ,MESSAGE passing (Computer science) - Abstract
Purpose The purpose of this paper is to extend complex-shaped discrete element method simulations from a few thousand particles to millions of particles by using parallel computing on department of defense (DoD) supercomputers and to study the mechanical response of particle assemblies composed of a large number of particles in engineering practice and laboratory tests.Design/methodology/approach Parallel algorithm is designed and implemented with advanced features such as link-block, border layer and migration layer, adaptive compute gridding technique and message passing interface (MPI) transmission of C++ objects and pointers, for high performance optimization; performance analyses are conducted across five orders of magnitude of simulation scale on multiple DoD supercomputers; and three full-scale simulations of sand pluviation, constrained collapse and particle shape effect are carried out to study mechanical response of particle assemblies.Findings The parallel algorithm and implementation exhibit high speedup and excellent scalability, communication time is a decreasing function of the number of compute nodes and optimal computational granularity for each simulation scale is given. Nearly 50 per cent of wall clock time is spent on rebound phenomenon at the top of particle assembly in dynamic simulation of sand gravitational pluviation. Numerous particles are necessary to capture the pattern and shape of particle assembly in collapse tests; preliminary comparison between sphere assembly and ellipsoid assembly indicates a significant influence of particle shape on kinematic, kinetic and static behavior of particle assemblies.Originality/value The high-performance parallel code enables the simulation of a wide range of dynamic and static laboratory and field tests in engineering applications that involve a large number of granular and geotechnical material grains, such as sand pluviation process, buried explosion in various soils, earth penetrator interaction with soil, influence of grain size, shape and gradation on packing density and shear strength and mechanical behavior under different gravity environments such as on the Moon and Mars. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
41. Numerical simulation of the influence of particle shape on the mechanical properties of rockfill materials.
- Author
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Han, Hongxing, Chen, Wei, Huang, Bin, and Fu, Xudong
- Subjects
ROCKFILLS ,PARTICLE size determination ,GRANULAR materials ,COMPUTER simulation ,DISCRETE element method - Abstract
Purpose This paper aims to propose a shape factor for granular materials based on particle shape. The scientific goal is to investigate the influence of particle shape on the mechanical properties of rockfill materials.Design/methodology/approach The method of generating four regular-shaped particles is based on the observation that most rockfill grains are regarded as like-triangle, like-rhombus, like-square and like-hexagon. A shape factor F that is developed using the Blaschke coefficient and a concave–convex degree is proposed. A biaxial compression test on rockfill materials under stress path is numerically simulated by discrete element method. The evolution of the shape factor F under the simulated stress paths is analyzed, and particle breakage rate, peak intensity and peak-related internal friction angle for rockfill materials are derived. A method of determining the shape factor F involved in the two functions is proposed.Findings A new micro-parameter is calibrated using the test data of one rockfill material. Particle shape greatly affects the particle breakage rate, peak intensity and peak-related internal friction angle for rockfill materials. The final experimental grading curves all approach the particle breakage grading curve proposed by Einav (the fractal dimension is 2.7).Originality/value This study proposes a shape factor F, which describes the geometric features of natural rockfill particles. The proposed shape factor F has a simple structure, and its parameters are easy to determine. The method provides an opportunity for a quantitative study on the particle shape of granular materials, and this study helps to better understand the influence of particle shape on the mechanical characteristics of rockfill materials. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
42. Discrete element approach in brittle fracture mechanics.
- Author
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Le, Ba Danh, Koval, Georg, and Chazallon, Cyrille
- Subjects
BRITTLE fractures ,STRUCTURAL failures ,FRACTURE mechanics ,DEFORMATIONS (Mechanics) ,STRENGTH of materials ,BRITTLENESS - Abstract
Purpose – The purpose of this paper is to use the discrete element method (DEM) to model the fracture behaviour of brittle materials in 2D. Design/methodology/approach – The material consists of a set of particles in contact with a close-packed structure. It allows the derivation of an expression for the stress intensity factor as a function of the contact forces near the crack tip. A classical failure criterion, based on the material's toughness, is then adopted for the analysis of crack propagation, represented by the contact loss between particles. Findings – The DEM approach is compared to two tensile cases (mode I); both presenting a monotonous convergence towards classical solutions for more precise discretization. Originality/value – The paper proposes a DEM approach in fracture mechanics of isotropic brittle materials entirely compatible with continuous classical theory. Hence the toughness value is directly introduced as a parameter of the material without any previous calibration of the DEM. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
43. Formulation and procedure to treat a discrete particle model as a continuum.
- Author
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Olmo, D. del and Serrano, A.
- Subjects
PARTICLES ,STRAINS & stresses (Mechanics) ,TORQUE ,DEFORMATIONS (Mechanics) ,FINITE element method - Abstract
Purpose – The purpose of this paper is to continue the path opened by previous researches that focused on the stress and deformation behaviour of discrete particle models, along with mechanical and morphological analyses. Design/methodology/approach – This work presents a formulation that allows the study of discrete particle models as if they were continuum. By knowing forces, torques, displacements and rotations that occur inside a particle media whenever a force is loading it, this formulation permits to obtain the stress, the torque, strain and rotation tensors of the media. Findings – These tensors are equivalent to the ones that would have been obtained by treating a discrete media as if it were a continuum. In addition, a procedure to apply the formulas to a numerical model has been detailed in the text. Finally, these formulas are compared to the one obtained from an energy balance approach to establish a connection between the forces and the increase of the energy produced inside the media. Originality/value – This paper presents a proposal of formulation to calculate the stress, torque, deformation and curvature tensor for discrete particle medias, welded or non-welded, in order to study them as if they were continuous. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
44. Prediction of industrial, biophysical and extreme geophysical flows using particle methods.
- Author
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Cleary, Paul W., Cohen, Raymond C.Z., Harrison, Simon M., Sinnott, Matthew D., Prakash, Mahesh, and Mead, Stuart
- Subjects
PARTICLES ,DYNAMICS ,FLUID dynamics ,SIMULATION methods & models ,SYSTEMS engineering - Abstract
Purpose – The purpose of this paper is to show how simulation of the flow of particulates and fluids using discrete element modelling (DEM) and smoothed particle dynamics (SPH) particle methods, offer opportunities for better understanding the dynamics of flow processes. Design/methodology/approach – DEM and SPH methods are demonstrated in a broad range of computationally-demanding applications including comminution, biomedical, geophysical extreme flow events (risk/disaster modelling), eating of food by humans and elite water-based sports. Findings – DEM is ideally suited to predicting industrial and geophysical applications where collisions between particles are the dominant physics. SPH is highly suited to multi-physics fluid flow applications in industrial, biophysical and geophysical applications. The advantages and disadvantages of these particle methods are discussed. Research limitations/implications – Research results are limited by the numerical resolution that can currently be afforded. Practical implications – The paper demonstrates the use of particle-based computational methods in a series of high value applications. Enterprises that share interests in these applications will benefit in their product and service development by adopting these methods. Social implications – The ability to model disasters provides governments and companies with the opportunity and obligation to use these to render knowable disasters which were previously considered unknowable. The ability to predict the breakdown of food during eating opens up opportunities for the design of superior performing foods with lower salt, sugar and fat that can directly contribute to improved health outcomes and can influence government food regulatory policy. Originality/value – The paper extends the scale and range of modelling of particle methods for demanding leading-edge problems, of practical interest in engineering and applied sciences. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
45. A parallel DEM approach with memory access optimization using HSFC.
- Author
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Cintra, Diogo Tenório, Willmersdorf, Ramiro Brito, Lyra, Paulo Roberto Maciel, and Lira, William Wagner Matos
- Subjects
DISCRETE element method ,HILBERT space ,LOAD balancing (Computer networks) ,ACCESS control ,COMPUTER simulation - Abstract
Purpose The purpose of this paper is to present a methodology for parallel simulation that employs the discrete element method (DEM) and improves the cache performance using Hilbert space filling curves (HSFC).Design/methodology/approach The methodology is well suited for large-scale engineering simulations and considers modelling restrictions due to memory limitations related to the problem size. An algorithm based on mapping indexes, which does not use excessive additional memory, is adopted to enable the contact search procedure for highly scattered domains. The parallel solution strategy uses the recursive coordinate bisection method in the dynamical load balancing procedure. The proposed memory access control aims to improve the data locality of a dynamic set of particles. The numerical simulations presented here contain up to 7.8 millions of particles, considering a visco-elastic model of contact and a rolling friction assumption.Findings A real landslide is adopted as reference to evaluate the numerical approach. Three-dimensional simulations are compared in terms of the deposition pattern of the Shum Wan Road landslide. The results show that the methodology permits the simulation of models with a good control of load balancing and memory access. The improvement in cache performance significantly reduces the processing time for large-scale models.Originality/value The proposed approach allows the application of DEM in several practical engineering problems of large scale. It also introduces the use of HSFC in the optimization of memory access for DEM simulations. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
46. A hybrid parallel DEM approach with workload balancing based on HSFC.
- Author
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Cintra, Diogo Tenório, Willmersdorf, Ramiro Brito, Lyra, Paulo Roberto Maciel, and Lira, William Wagner Matos
- Subjects
HILBERT space ,DIGITAL elevation models ,DISCRETE element method ,DOMAIN decomposition methods ,COMPUTER simulation - Abstract
Purpose The purpose of this paper is to present a methodology of hybrid parallelization applied to the discrete element method that combines message-passing interface and OpenMP to improve computational performance. The scheme is based on mapping procedures based on Hilbert space-filling curves (HSFC).Design/methodology/approach The methodology uses domain decomposition strategies to distribute the computation of large-scale models in a cluster. It also partitions the workload of each subdomain among threads. This additional procedure aims to reach higher computational performance by adjusting the usage of message-passing artefacts and threads. The main objective is to reduce the communication among processes. The work division by threads employs HSFC in order to improve data locality and to avoid related overheads. Numerical simulations presented in this work permit to evaluate the proposed method in terms of parallel performance for models that contain up to 3.2 million particles.Findings Distinct partitioning algorithms were used in order to evaluate the local decomposition scheme, including the recursive coordinate bisection method and a topological scheme based on METIS. The results show that the hybrid implementations reach better computational performance than those based on message passing only, including a good control of load balancing among threads. Case studies present good scalability and parallel efficiencies.Originality/value The proposed approach defines a configurable execution environment for numerical models and introduces a combined scheme that improves data locality and iterative workload balancing. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
47. A non-locking composite tetrahedron element for the combined finite discrete element method.
- Author
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Lei, Zhou, Rougier, Esteban, Knight, Earl E., Frash, Luke, Carey, James William, and Viswanathan, Hari
- Subjects
TETRAHEDRA ,DISCRETE element method ,ELASTICITY ,MATHEMATICAL decomposition ,DEFORMATIONS (Mechanics) - Abstract
Purpose In order to avoid the problem of volumetric locking often encountered when using constant strain tetrahedral finite elements, the purpose of this paper is to present a new composite tetrahedron element which is especially designed for the combined finite-discrete element method (FDEM).Design/methodology/approach A ten-noded composite tetrahedral (COMPTet) finite element, composed of eight four-noded low order tetrahedrons, has been implemented based on Munjiza’s multiplicative decomposition approach. This approach naturally decomposes deformation into translation, rotation, plastic stretches, elastic stretches, volumetric stretches, shear stretches, etc. The problem of volumetric locking is avoided via a selective integration approach that allows for different constitutive components to be evaluated at different integration points.Findings A number of validation cases considering different loading and boundary conditions and different materials for the proposed element are presented. A practical application of the use of the COMPTet finite element is presented by quantitative comparison of numerical model results against simple theoretical estimates and results from acrylic fracturing experiments. All of these examples clearly show the capability of the composite element in eliminating volumetric locking.Originality/value For this tetrahedral element, the combination of “composite” and “low order sub-element” properties are good choices for FDEM dynamic fracture propagation simulations: in order to eliminate the volumetric locking, only the information from the sub-elements of the composite element are needed which is especially convenient for cases where re-meshing is necessary, and the low order sub-elements will enable robust contact interaction algorithms, which maintains both relatively high computational efficiency and accuracy. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
48. Combined finite-discrete element method modeling of rockslides.
- Author
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Zhou, Wei, Yuan, Wei, Ma, Gang, and Chang, Xiao-Lin
- Subjects
ROCKSLIDES ,DISCRETE element method ,COHESIVE strength (Mechanics) ,ROCK slopes ,SIMULATION methods & models - Abstract
Purpose – The purpose of this paper is to propose a novel combined finite-discrete element method (FDEM), based on the cohesive zone model, for simulating rockslide problems at the laboratory scale. Design/methodology/approach – The combined FDEM is realized using ABAQUS/Explicit. The rock mass is represented as a collection of elastic bulk elements glued by cohesive elements with zero thickness. To reproduce the tensile and shear micro-fractures in rock material, the Mohr-Coulomb model with tension cut-off is employed as the damage initiation criterion of cohesive elements. Three simulated laboratory tests are considered to verify the capability of combined FDEM in reproducing the mechanical behavior of rock masses. Three slope models with different joint inclinations are taken to illustrate the application of the combined FDEM to rockslide simulation. Findings – The results show that the joint inclination is an important factor for inducing the progressive failure behavior. With a low joint inclination, the slope failure process is observed to be a collapse mode. As the joint inclination becomes higher, the failure mode changes to sliding and the steady time of rock blocks is shortened. Moreover, the runout distance and post-failure slope angle decrease as the joint inclination increases. Originality/value – These studies indicate that the combined FDEM performed within ABAQUS can simulate slope stability problems for research purposes and is useful for studying the slope failure mechanism comprehensively. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
49. Calibrating the microscopic properties of quartz sand with coupled CFD-DEM framework.
- Author
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Derakhshani, Sayed M., Schott, Dingena L., and Lodewijks, Gabriel
- Subjects
SAND ,DISCRETE element method ,COMPUTATIONAL fluid dynamics ,CALIBRATION ,SIMULATION methods & models - Abstract
Purpose – The macroscopic properties of dried sand can be correctly modelled when the accurate determination of the microscopic properties is available. The microscopic properties between the particles such as the coefficients of rolling (µ
r ) and sliding (µs ), are numerically determined in two different ways: with and without considering the fluid effect. In an earlier study, the microscopic properties were determined by discrete element method (DEM) and without considering the air effect on the macroscopic properties such as the Angle of Repose. The purpose of this paper is to recalibrate the microscopic properties through a coupling between the DEM and computational fluid dynamics (CFD). Design/methodology/approach – The first step is dedicated to the calibration of the CFD-DEM model through modelling a single particle sedimentation within air, water, and silicon oil. The voidage and drag models, the grid size ratio (D/dx), the domain size ratio (W/D), and the optimum coupling interval between the CFD and DEM were investigated through comparing the CFD-DEM results with the analytical solution and experimental data. The next step is about modelling an Hourglass with the calibrated CFD-DEM model to recalibrate the µr and µs of dried sand particles. Findings – It was concluded that the air has a minor effect on the macroscopic properties of the dried sand and the µr and µs that were obtained with the DEM can be utilized in the CFD-DEM simulation. Originality/value – Utilizing the granulometry of dried quartz sand in the calibration process of the CFD-DEM method has raised the possibility of using the µr and µs for other applications in future studies. [ABSTRACT FROM AUTHOR]- Published
- 2016
- Full Text
- View/download PDF
50. Tensile test simulation of high-carbon steel by discrete element method.
- Author
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Chen, Guangming, Schott, Dingena L., and Lodewijks, Gabriel
- Subjects
TENSILE tests ,CARBON steel ,DISCRETE element method ,STIFFNESS (Mechanics) ,PARTICLE motion - Abstract
Purpose – The tensile test is one of the fundamental experiments used to evaluate material properties. Simulating a tensile test can be a replacement of experiments to determine mechanical parameters of a continuous material. The paper aims to discuss these issues. Design/methodology/approach – This research uses a new approach to model a tensile test of a high-carbon steel on the basis of discrete element method (DEM). In this research, the tensile test specimen was created by using a DEM packing theory. The particle-particle bond model was used to establish the internal forces of the tensile test specimen. The particle-particle bond model was first tested by performing two-particle tensile test, then was adopted to simulate tensile tests of the high-carbon steel by using 3,678 particles. Findings – This research has successfully revealed the relationships between the DEM parameters and mechanical parameters by modelling a tensile test. The parametric study demonstrates that the particle physical radius, particle contact radius and bond disc radius can significantly influence ultimate stress and Young’s modulus of the specimen, whereas they slightly impact elongation at fracture. Increasing the normal and shear stiffness, the critical normal and shear stiffness can enable the increase of ultimate stress, however, up to maximum values. Research limitations/implications – To improve the particle-particle bond model to simulate a tensile test for high-carbon steel, the damping factors for compensating energy loss from transition of particle motions and failure of bonds are required. Practical implications – This work reinforces the knowledge of applying DEM to model continuous materials. Originality/value – This research illustrates a new approach to model a tensile test of a high-carbon steel on the basis of DEM. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
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