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distinct element method simulation of mechanical properties of material layer of pellet belt roasting machine

Journal of Iron and Steel Research International 2024年第11期31卷 2633-2644页

作者： Yin-hua Tang Xing-wang Li Xu Gao Tao Yang Hong-ming Long Jie Lei School of Metallurgical Engineering Anhui University of TechnologyMa’anshan243032AnhuiChina Xinyu Iron and Steel Group Co. Ltd.Xinyu338000JiangxiChina Key Laboratory of Metallurgy Engineering&Resources Recycling(Anhui University of Technology) Ministry of EducationMa’anshan243002AnhuiChina

The thick layer and graded feeding technology of a belt roasting machine is an effective method for improving the production efficiency and quality index of pellet production,and a reasonable design of the mechanical structure of the layer is the basis for optimizing the heat and mass transfer performance of the *** effect and von Mises yield criterion were used to establish a simplified mathematical model describing the elastic and plastic deformation of the green pellet under the action of an external *** mechanical characteristics of extrusion,contact,and elastic-plastic deformation between green pellet particles in the material layer of the belt roasting machine were modeled using EDEM *** a green pellet size of 12 mm,as the layer height increases from 300 to 1000 mm,the maximum vertical pressure on the pellets increases from 11.64 to 24.01 N,and the porosity decreases from 27.04%to 22.01%.As the layer height increases,the contact between the green pellets becomes more intense,and the force chain structure of the layer becomes more stable;the Janssen effect is observed when the layer reaches 700 *** compressive strength of the green pellets is linearly related to the particle size,and the compressive strength increases with an increase in particle *** a layer height of 600 mm,as the particle size of the green pellets increases from 8 to 20 mm,the maximum vertical pressure increases from 7.54 to 44.16 N,and the porosity increases from 23.20%to 31.47%,while the yield per unit of the layer decreased by 12.1%.Small particles have a more stable force chain structure,larger comparative area,and higher production efficiency;however,their compressive strength is *** particles have higher compressive strength and good permeability in the layer,but the production efficiency is relatively *** actual production,a variety of factors should be integrated to optimize the feeding,and a multi-granularity graded feeding is the most ideal

关键词： Belt roasting machine distinct element method Green pellet Thick material layer Mechanical property

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Simplified Micro-Modeling of a Masonry Cross-Vault for Seismic Assessment Using the distinct element method

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INTERNATIONAL JOURNAL OF ARCHITECTURAL HERITAGE 2024年第12期18卷 1915-1948页

作者： Oktiovan, Y. P. Davis, L. Wilson, R. Dell'Endice, A. Mehrotra, A. Pulatsu, B. Malomo, D. Delft Univ Technol Fac Civil Engn & Geosci Delft Netherlands McGill Univ Dept Civil Engn Montreal PQ Canada Carleton Univ Dept Civil & Environm Engn Ottawa ON Canada Swiss Fed Inst Technol Inst Technol Architecture Zurich Switzerland Delft Univ Technol Fac Civil Engn & Geosci Stevinweg 1 NL-2628 CN Delft Netherlands

The assessment of the seismic performance of unreinforced masonry cross-vaults is still a challenge in numerical analysis, due to complex curved geometries and bond patterns, and uncertainties related to the selection of adequate modeling strategies, including but not limited to that of material properties, damping scheme, and unit/joint idealization. This paper presents the results of a collaborative effort to validate, against the shake table test of both unstrengthened and strengthened masonry cross-vault specimens as part of the SERA Project Blind Prediction and Post-diction Competition, various discontinuum-based numerical approaches. First, the geometry of the cross-vault is created using a Python-based computational framework to accurately represent the brick arrangement and the shape of the vault. Then, the geometry is converted into an assemblage of deformable blocks and analyzed using the distinct element method (DEM). An elasto-softening contact model based on fracture energy is implemented in the masonry joints to simulate crushing, tensile, and shear failures. The performance of the proposed strategy, conceived for the unstrengthened configuration of the tested vault specimen and then adapted to include the presence of cementitious repairs, shows satisfactory agreement with both qualitative and quantitative experimental responses, also revealing critical insights and lessons learned through the blind/post-prediction exercise.

关键词： Blind prediction Cross-vault distinct element method Post-diction Softening contact models Unreinforced masonry

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Determination of a destressing scheme for the stiff main roof of an evaporite deposit using distinct element method

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EARTH SCIENCE INFORMATICS 2025年第3期18卷 1-19页

作者： Konuk, Cem Noyan Yardimci, Ahmet Gunes Middle East Tech Univ Min Engn Dept Ankara Turkiye

Solution mining in thick evaporites leaves large underground openings with no roof support. Stiff strata overlaying the production caverns pose a risk of sudden collapse as excessive loads lead to the sudden release of strain energy. This violent failure threatens the operational sustainability and safety. Destressing methods are commonly used to mitigate the risk by inducing fracture networks in the stiff layers. This study employs a discontinuum based numerical code to investigate the alternative destressing schemes on a typical solution mine layout. Regarded the operational practice and economy, the ribbon and borehole patterns were simulated with different configurations. Discrete Fracture Networks were used for implementation of the fractured region. While the ribbons were examined for spacings of 30 m, 60 m and 90 m, the boreholes were studied for straight and staggered patterns. A typical production with a single solution cavern was simulated on a staged manner and the stress-strain histories were monitored. Comparing the model results, the most viable destressing scheme was determined for solution mining. In advance, stress management was also investigated for destressing wherever multiple stiff layers exist.

关键词： Destressing Strata control Solution mining distinct element method

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A contact-based constitutive model for the numerical analysis of masonry structures using the distinct element method

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COMPUTERS & STRUCTURES 2024年 303卷

作者： Oktiovan, Y. P. Pulatsu, B. Lemos, J. V. Rots, J. G. Delft Univ Technol Fac Civil Engn & Geosci Stevinweg 1 NL-2628CN Delft Netherlands Carleton Univ Dept Civil & Environm Engn Ottawa ON Canada Natl Lab Civil Engn LNEC Lisbon Portugal

This study presents a robust contact constitutive model in the distinct element method (DEM) framework for simulating the mechanical behavior of masonry structures. The model is developed within the block-based modeling strategy, where the masonry unit is modeled as deformable blocks with potential crack surfaces in the middle of the bricks, while the mortar joints are defined as zero-thickness interfaces. The modeling strategy implements multi-surface plasticity with damage mechanics, including a tension cut-off, Coulomb failure criterion, and an elliptical compressive cap for the damage in tension, shear, and compression, respectively. Two new features are introduced in this contact model: a piecewise linear softening function for strength degradation in tension and shear and a hardening/softening function to phenomenologically define the compressive damage of masonry composite into the unit-mortar interface. The constitutive model is implemented in commercial DEM software using the small displacement configuration and validated against material and experimental tests on masonry walls subjected to constant pre-compression and monotonically increasing in-plane load. The experimental and numerical results regarding the force-displacement relationship and damage pattern produced by the proposed constitutive model are compared and critically discussed, demonstrating the capability of DEM coupled with the suitable constitutive law in simulating the behavior of masonry structures.

关键词： Masonry Constitutive model distinct element method Explicit integration scheme Multi-surface plasticity Damage mechanics

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Crack Propagation in Heterogeneous Gravity Dams Due to Overflow Using Polygonal Grain-Based distinct element method

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ROCK MECHANICS AND ROCK ENGINEERING 2024年第7期57卷 5017-5046页

作者： Badakhshan, Ehsan Veylon, Guillaume Peyras, Laurent Vaunat, Jean Aix Marseille Univ RECOVER INRAE Aix En Provence France Univ Politecn Cataluna Dept Civil Engn Barcelona Spain

Cracks are always a serious concern in the stability analysis of gravity dams. One of the main reasons for the initiation of cracks is overflow. In most previous crack propagation analyses, the presence of water and different configuration of the materials is not considered. In this study, to adequately evaluate the crack development in gravity dams subjected to overflow, a polygonal grain-based model (P-GBM), enriched in considering the influence of joint roughness through the Barton-Bandis (B-B) model, is employed in a distinct element framework. To take into account the effect of joint softening on the tensile strength of cracks, the B-B model is improved by a polynomial tensile law. Then, the model is verified by Brazilian and Uniaxial tests containing various combinations of rock and mortar. The numerical results demonstrated a good agreement by the experiments in terms of the strength characteristics and fracture phenomenon. Then, failure analysis for two heterogeneous gravity dams with various complexities under the reservoir overflow is investigated. Performing the risk analysis with different flood scenarios revealed that because of considering the joint-water interactions, the P-GBM suitably predicts the crack propagation. The crack path begins nearly horizontal and then turns downwards toward the dam's toe. Once cracks form, they act as conduits for water movement and allow more water to penetrate, which increases the pore water pressure and accelerates the propagation of cracks. Also, the critical dam displacements in terms of cracking (initiation, horizontal, and inclined parts) are investigated with different approaches, such as the tangent intersection method, the external second-order work, and the broken joint index. The results revealed that all three techniques determine suitably the critical heights and horizontal displacements in various flood scenarios. The polygonal grain-based technique simulates the rock and mortar combinations in good agree

关键词： Polygonal grain-based model distinct element method Crack propagation Gravity dam

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Polyaxial Stress-Dependent Tensorial Permeability Variations of a Columnar Jointed Rock Mass: Insights from 3D distinct element method

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INDIAN GEOTECHNICAL JOURNAL 2024年 1-18页

作者： Pothana, Prasad Rasouli, Vamegh Ling, Kegang Univ North Dakota Coll Engn & Mines Energy & Petr Engn 2844 Campus Rd Grand Forks ND 58202 USA Univ Wyoming Coll Engn & Phys Sci Energy & Petr Engn 1000 E Univ Ave Laramie WY 82071 USA

Stress-induced permeability changes in geological formations have implications for various geo-engineering applications. Fractures are the predominant fluid flow pathways within tight geological formations such as jointed basaltic rock mass. Three-dimensional permeability variations of a columnar jointed rock mass using the three-dimensional block distinct element method are investigated. First, a permeability tensor is constructed by simulating fluid flow through joint sets using cubic law and determining its principal components through eigenvector analysis. Subsequently, numerical simulations are conducted to gain insights into the impact of principal stresses on joint deformation and fluid flow. Joint deformation is controlled by the joint's mechanical properties, contact models, and stress state. Different isotropic and anisotropic stress loading scenarios on the permeability tensor evolution are investigated. The research findings indicate that isotropic stress loading led to uniform normal compression on fractures, resulting in a monotonic reduction of all permeability tensor components and increased permeability anisotropy. Anisotropic stress loading, particularly the intermediate stress, often neglected, significantly influenced the rock's overall permeability. While the directions of the principal components remained consistent during isotropic loading, they exhibited changes in both direction and magnitude during anisotropic loading. The relative angle between the joint plane and the principal stresses was crucial in controlling joint behavior, including normal compression, shear failure, and dilation. Additionally, data analysis revealed that the exponential empirical model provided an excellent fit for permeability-stress data.

关键词： Stress-dependent permeability Fractured rock distinct element method Intermediate principal stress Permeability tensor

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The propagation of hydraulic fracture in layered coal seam: a numerical simulation considering the interface thickness based on the distinct element method

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FRONTIERS IN ENERGY RESEARCH 2024年 11卷

作者： Gao, Hongye Jia, Baoshan Lei, Yun Zheng, Yongxiang Shi, Bin Wei, Haiyang Zhang, Tongjing Wang, Wei Niu, Qinghe Liaoning Tech Univ Coll Safety Sci & Engn Fuxin Peoples R China Liaoning Tech Univ Key Lab Mine Thermodynam Disasters & Control Minist Educ Huludao Peoples R China China Coal Technol & Engn Grp Corp Shenyang Res Inst State Key Lab Coal Mine Safety Technol Shenyang Peoples R China Shijiazhuang Tiedao Univ Key Lab Rd & Railway Engn Safety Control Minist Educ Shijiazhuang Peoples R China Hebei Technol & Innovat Ctr Safe & Efficient Min M Shijiazhuang Peoples R China CNPC Xibu Drilling Engn Co Ltd Downhole Operat Co Karamay Peoples R China

The intercalated layer of coal seam plays an important role in the propagation of hydraulic fracturing. To understand the role of the intercalated layer, a composite coal seam model considering the thickness of the intercalated layer was established. Based on the block distinct element method, the effects of rock structure (thickness of the coal seam and intercalated layer), rock properties (elastic modulus), and construction parameters (injection rate and fluid viscosity) on the penetration behavior of hydraulic fractures were analyzed. The results show that the intercalated layers influence the fracture deflection and have a hindering effect on fracture propagation. The thickness of the intercalated layer affects the stress on the bedding plane and the front edge of the fractures. On the contrary, the thickness of the coal seam mainly affects the penetration ability of hydraulic fractures and the extent of hydraulic fracture propagation. In addition, the elastic modulus of the intercalated layers and coal seams affects the hindering effect of the intercalated layer. The high injection rates reduce the hindering effect of the intercalated layer. When fracturing with a high-viscosity fluid, fractures are more likely to enter the intercalated layer. However, excessively high viscosity can make it difficult for fractures to penetrate the intercalated layer. This study can provide theoretical guidance for the fracturing of composite coal seams.

关键词： hydraulic fracturing layered coal seam distinct element method thickness intercalated layer

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Mesoscopic distinct element method for Carbon Nanotubes: From Workstation to Massively Parallel Simulations

Mesoscopic Distinct Element Method for Carbon Nanotubes: Fro...

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作者： Drozdov, Grigorii University of Minnesota

学位级别：Ph.D.

Carbon nanotubes (CNT), artificially synthesized hollow cylinders with graphitic walls, have attracted significant attention as components for developing ultrastrong materials. However, scaling up the superb mechanical properties of individual CNTs to the material level poses significant challenges related mainly to the poor inter-tube load transfer between CNTs. The design of better CNT materials could benefit from guidance through numerical modeling, but neither molecular dynamics techniques nor finite element modeling could provide necessary tools for modeling the mechanics of CNT assemblies. New mesoscopic methods are needed and among coarse-grained mesoscopic models available, our mesoscopic distinct element method (mDEM) model provides premium accuracy and efficiency of bonded and non-bonded interactions as well as unprecedented length scales. This thesis is devoted to the development, enhancement, and application of the mDEM model to the modeling of CNT materials. In this work, mDEM, previously implemented in the DEM code PFC3D, is cast into an enhanced vector format and scalable parallelized with the message passing interface (MPI) technology, as enabled by waLBerla DEM multiphysics framework. The new capability allows for the modeling of large assemblies of CNTs, while distributing the computation over thousands of computational cores. With the parallelized implementation of the mDEM model in waLBerla we are able to perform unprecedented simulations, including single-walled CNT films densification and nanoindentation processing, and double-walled CNT yarns formation by stretching CNT "sock" materials. Furthermore, with a tabulation technique, mDEM is expanded to non-cylindrical collapsed CNTs. Finally, in another enhancement of mDEM model, we lay a foundation for simulation of CNT assemblies interaction with fluids.

关键词： Carbon nanotubes distinct element method Mesoscale simulations

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Seismic fragility analysis and reliability evaluation for ancient stone pagoda using distinct element method

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RESULTS IN ENGINEERING 2024年 23卷

作者： Tra, Sanh N. Kim, Se Hyun Shin, Jiuk Lee, Do Hyung Park, Heon-Joon Lee, Kihak Sejong Univ Deep Learning Architecture Res Ctr Dept Architectural Engn 209 Neungdong Ro Seoul 05006 South Korea Natl Res Inst Cultural Heritage Safety & Disaster Prevent Div Daejeon 34122 South Korea Gyeongsang Natl Univ Dept Architectural Engn Jinju 52828 South Korea Paichai Univ Dept Civil Environm & Railrd Engn 155-40 Baejaero Daejeon 35345 South Korea Seoul Natl Univ Sci & Technol SEOULTECH Dept Civil Engn Seoul 01811 South Korea

This study presents an application of performance-based assessment to establish fragility functions and evaluate the seismic reliability of an ancient stone pagoda in Korea. The pagoda was constructed of stone elements which were stacked over each other in layers without bonding material. To account for the discrete nature of this kind of structural configuration, the distinct element method is used to perform the incremental dynamic analysis to develop fragility functions. Three performance levels are specified on the capacity curve which is established based on non-linear pushover analysis. The randomness in seismic demand generation was considered when exciting the pagoda by a set of 23 input ground motion records, which were scaled into different intensity levels. The seismic response of the pagoda under different ground motions at several peak ground acceleration levels shows that the predominant frequency of the excitation is closely related to the behavior of this kind of structure. Ground motions with lower predominant frequency values induce stronger distortion to the pagoda than the ones with higher predominant frequency. The fragility functions estimated by maximum likelihood method show that earthquakes with peak ground motion of 0.469 g have a 50% probability of causing a collapse on the pagoda in the most conservative assessment. The probability of the pagoda collapsing within 50 years is 1.65% for the most earthquake-vulnerable site among the sites considered in the study.

关键词： Stone pagoda distinct element method Seismic reliability Fragility analysis Incremental dynamic analysis

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Influence of polymeric and cross-linked nano-hole interfaces on the tensile response of carbon nanotube bundles: A mesoscopic distinct element method approach

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EXTREME MECHANICS LETTERS 2023年 65卷

作者： Kataria, Aditya Wang, Yuezhou Mujumdar, Kedar Dumitrica, Traian Univ Minnesota Dept Mech Engn Minneapolis MN 55455 USA Minnesota State Univ Integrated Engn Mankato MN 56001 USA

While atomistic simulations can quantify the nano-mechanical properties of carbon nanotube (CNT) interfaces, they become impractical when it comes to predicting their functions within CNT assemblies. Using the mesoscopic distinct element method (MDEM) for CNTs, we perform coarse-grained multiscale simulation to compare the impact of polymeric and cross-linking interfaces in highly discontinuous CNT bundle and network assemblies subjected to simple tension. Viscous friction and contact shear bonds are used in MDEM to capture the polymeric and cross-linking nano-mechanics computed separately with atomistic methods. Cross-linking is found to be the most effective at increasing elastic moduli and tensile strengths of the CNT bundles. These properties can be diminished by the nano-holes in the CNT wall associated with irradiation-generated cross-linking and captured here into the contacts representing CNT stretching. Simulations indicate the need to balance the benefits and drawbacks of the radiation-induced morphological changes in order to manufacture CNT yarns with superior tensile characteristics.

关键词： distinct element method Carbon Nanotubes Strength Irradiation

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