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Numerical simulation study on particle breakage behavior of granular materials in confined compression tests

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Particuology 2023年第3期74卷 18-34页

作者： Yang Yu Guangsi Zhao Minghui Ren State Key Laboratory for Geomechanics and Deep Underground Engineering School of Mechanics and Civil EngineeringChina University of Mining and TechnologyXuzhou221116China

In order to study the fragmentation law,the confined compression experiment of granular assemblies has been conducted to explore the particle breakage characteristic by DEM approach in this *** is shown that contact and contact force during the loading process gradually transform from anisotropy to ***,two particle failure modes caused by different contact force states are analyzed,which are single-through-crack failure and multi-short-crack *** the vertical distribution of the number of cracks and the four characteristic stress distributions(the stress related to the maximum contact force,the major principal stress,the deviatoric stress and the mean stress),it is pointed out that the stress based on the maximum contact force and the major principal stress can reflect the distribution of cracks *** addition,the size effect of particle crushing indicates that small size particles are prone to *** lateral pressure coefficient of four size particles during the loading process is analyzed to explain the reason for the size effect of particle breakage.

关键词： granular materials Confined compression Particle breakage Meso-mechanics Discrete element method

Flow characteristics of nonspherical granular materials simulated with multi-superquadric elements

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Particuology 2021年第1期19卷 25-36页

作者： Siqiang Wang Shunying Ji State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of TechnologyDalian 116023China

The superquadric equation is typically used to mathematically describe nonspherical particles and construct particle shapes with different surface sharpness and aspect ***,nonspherical elements constructed using the superquadric equation are strictly convex,limiting their engineering *** this study,a multi-superquadric model based on a superquadric equation is *** model combines several superquadric elements that can be used to construct concave and convex particle *** tests are performed to examine the applicability of the multi-superquadric *** first involves a comparison of theoretical results for a single spherocylinder impacting a flat *** second involves the formation of a nonspherical granular *** third investigates the effects of the particle shape on the hopper discharge and angle of *** final test evaluates the mixing behaviors of granular materials within a horizontally rotating *** tests demonstrate the applicability of the multi-superquadric approach to nonspherical granular ***,the effects of particle shape on the packing density,discharge rate,angle of repose,and Lacey mixing index are *** indicate that concave particles have a lower packing density,flow rate,and mixing rate and higher angles of repose than convex *** of elements becomes more pronounced for concave particles and results in local cluster structures,thereby enhancing the stability of granular systems and limiting sliding or rotation between nonspherical particles.

关键词： Multi-superquadric approach Nonspherical elements Concave particles Discrete element method granular materials

“Relay-mode”promoting permeation of water-based fire extinguishing agent in granular materials porous media stacks

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Chinese Journal of Chemical Engineering 2022年第7期35卷 98-112页

作者： Kang Wang Wei Tan Liyan Liu School of Chemical Engineering and Technology Tianjin UniversityTianjin 300350China Tianjin Key Laboratory of Chemical Process Safety and Equipment Technology Tianjin 300350China

Water-based fire extinguishing agent is the main means to deal with smoldering ***,due to the hydrophobic properties of the particle surface,the porous medium channel provide resistance and slow down the extinguishing agent flow during the downward permeation *** promote the liquid permeation process in such porous media,this work studied liquid imbibition process and analyzed the oscillating and attenuating process of liquid level in capillary channel by theoretical,experimental,and numerical *** empirical mathematical equation was proposed to describe the oscillating process,and the effects of the capillary diameter and contact angle parameters on the transportation process were *** on this,the“relay-mode”was proposed to promote the liquid transportation ***,the transient simulation results of liquid permeation in coal stacks showed when the liquid flowed through the channel with changed diameter from large to small ones,the transportation distance was several times longer than that through the unidiameter *** trend of liquid“relay-mode”in capillaries can be used to promote the permeation in granular materials porous media *** relevant results also provide new thoughts to develop the water-based fire extinguishing agents and then improve the firefighting efficiency of deep-seated fire in porous media stacks.

关键词： granular materials Porous media Safety Permeation Water-based fire extinguishing agent

On the degradation of granular materials due to internal erosion

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Acta Mechanica Sinica 2015年第5期31卷 685-697页

作者： Xiaoliang Wang Jiachun Li Key Laboratory for Mechanics in Fluid Solid Coupling Systems Institute of MechanicsChinese Academy of Sciences

A new state-based elasto-plastic constitutive relationship along with the discrete element model is established to estimate the degradation of granular materials due to internal *** essential effects of internal erosion such as the force network damage and relaxation are proposed and then incorporated into the constitutive relationship to formulate internal erosion impacts on the mechanical behavior of granular *** manifestations in the degradation of granular materials,such as reduction of peak strength and dilatancy are predicted by the modified constitutive relationship in good agreement with the discrete element method（DEM）*** particular,the sudden reduction of stress for conspicuous mass erosion in a high stress state is captured by force network damage and the relaxation *** is concluded that the new modified constitutive relationship is a potential theory to describe the degradation of granular materials due to internal erosion and would be very useful,for instance,in the prediction and assessment of piping disaster risk during the flood season.

关键词： Internal erosion Degradation granular materials Discrete element method

Mathematical Model for the Drying Process of granular materials in a Fluidized Bed

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International Journal of Minerals,Metallurgy and materials 2000年第4期14卷 296-300页

作者： Xiulan Huai, Li Wang, Zhiyun Qu ( Mechanical Engineering School, University of Science and Technology Beijing, Beijing 100083, China Chemical Industry Research Institute of Shanxi, Taiyuan 030031, China) Mechanical Engineering School University of Science and Technology Beijing Beijing 100083 China Chemical Industry Research Institute of Shanxi Taiyuan 030031 China

The experiment of granular materials, barley, drying in a fluidized bed was carried out to investigate the influence of the factors, inlet air temperature, air moisture, bed height and original moisture content of the dried materials on drying process. Based on the experimental data, a corresponding mathematical model is presented. As a conclusion, a higher inlet air temperature and a reasonable bed height should be used so as to increase the dring rate and to improve the product quality.

关键词： fluidization granular materials drying, experimental investigation mathematical model Information

A simulation based on the cosserat continuum model of the vortex structure in granular materials

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Acta Mechanica Solida Sinica 2015年第2期28卷 182-186页

作者： Cun Yu Xihua Chu Yuanjie Xu Department of Engineering Mechanics Wuhan University

Displacement fluctuation is the difference between the real displacement and the affine displacement in deforming granular materials. The discrete element method （DEM） is widely used along with experimental approaches to investigate whether the displacement fluctuation represents the vortex structure. Current research suggests that the vortex structure is caused by the cooperative motion of particle groups on meso-scales, which results in strain localization in granular materials. In this brief article, we investigate the vortex structure using the finite element method （FEM） based on the Cosserat cor[tinuum model. The numerical example focuses on the relationship between the vortex structure and the shear bands under two conditions：（a） uniform granular materials; （b） granular materials with inclusions. When compared with distributions of the effective strain and the vortex structure, we find that the vortex structure coexists with the strain localization and originates from the stiffness cooperation of different locations in granular materials at the macro level.

关键词： granular materials vortex structure strain localization Cosserat continuum model

Multi-layer perceptron-based data-driven multiscale modelling of granular materials with a novel Frobenius norm-based internal variable

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第6期16卷 2198-2218页

作者： Mengqi Wang Y.T.Feng Shaoheng Guan Tongming Qu Zienkiewicz Centre for Computational Engineering Faculty of Science and EngineeringSwansea UniversitySwanseaWalesSA18EPUK Institute of Theoretical and Computational Physics Graz University of TechnologyGraz8010Austria Department of Civil and Environmental Engineering Hong Kong University of Science and TechnologyClearwater BayKowloonHong KongChina

One objective of developing machine learning(ML)-based material models is to integrate them with well-established numerical methods to solve boundary value problems(BVPs).In the family of ML models,recurrent neural networks(RNNs)have been extensively applied to capture history-dependent constitutive responses of granular materials,but these multiple-step-based neural networks are neither sufficiently efficient nor aligned with the standard finite element method(FEM).Single-step-based neural networks like the multi-layer perceptron(MLP)are an alternative to bypass the above issues but have to introduce some internal variables to encode complex loading *** this work,one novel Frobenius norm-based internal variable,together with the Fourier layer and residual architectureenhanced MLP model,is crafted to replicate the history-dependent constitutive features of representative volume element(RVE)for granular *** obtained ML models are then seamlessly embedded into the FEM to solve the BVP of a biaxial compression case and a rigid strip footing *** obtained solutions are comparable to results from the FEM-DEM multiscale modelling but achieve significantly improved *** results demonstrate the applicability of the proposed internal variable in enabling MLP to capture highly nonlinear constitutive responses of granular materials.

关键词： granular materials History-dependence Multi-layer perceptron(MLP) Discrete element method FEM-DEM Machine learning

Simulation of triaxial response of granular materials by modified DEM

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Science China(Physics,Mechanics & Astronomy) 2014年第12期57卷 2297-2308页

作者： WANG XiaoLiang LI JiaChun Key Laboratory for Mechanics in Fluid Solid Systems Institute of Mechanics Chinese Academy of Sciences

A modified discrete element method(DEM)with rolling effect taken into consideration is developed to examine macroscopic behavior of granular materials in this *** analysis is firstly performed to establish the relationship between macroscopic mechanical behavior,mesoscale contact parameters at particle level and external loading *** is found that only four dimensionless parameters may govern the macroscopic mechanical behavior in *** numerical triaxial apparatus was used to study their influence on the mechanical behavior of granular *** parametric study indicates that Poisson’s ratio only varies with stiffness ratio,while Young’s modulus is proportional to contact modulus and grows with stiffness ratio,both of which agree with the micromechanical *** peak friction angle is dependent on both inter-particle friction angle and rolling *** dilatancy angle relies on inter-particle friction angle if rolling stiffness coefficient is sufficiently ***,we have recommended a calibration procedure for cohesionless soil,which was at once applied to the simulation of Chende sand using a series of triaxial compression *** responses of DEM model are shown in quantitative agreement with *** addition,stress-strain response of triaxial extension was also obtained by numerical triaxial extension tests.

关键词： granular materials rolling resistance DEM calibration YADE

Discrete numerical modeling of granular materials considering crushability

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Journal of Mountain Science 2017年第4期14卷 758-770页

作者： QIAN Jian-gu GU Jian-bo GU Xiao-qiang HUANG Mao-song Key Laboratory of Geotechnieal and Underground Engineering of Ministry of Education Tongji UniversityShanghai 200092China Department of Geotechnical Engineering Tongji UniversityShanghai 200092China

The aim of this study is to numerically investigate the influence of particle breakage on the mechanical behavior of granular materials using a discrete element method(DEM). To enable particle crushing, non-crushable elementary particles are boned together to represents the granular aggregates which can be crushed when the external force exceeds its strength. The flaw of the aggregate was also modeled by randomly distributed void. Single particle crushing tests were carried out to determine the distribution of particle strength. The results of single particle crushing tests illustrate that the simulated single particle fracture strength and pattern agree well with the Weibull's distribution *** oedometer tests, drained monotonic and cyclic triaxial tests were also carried out to investigate the crushing of the aggregates and the associated mechanical behaviors. The effect of confining pressure on the crushing of aggregates and the mechanical behavior was also analyzed. It was found that the peak stress and dilation decrease significantly when particle crushing was *** deformation behavior of the specimen is essentially controlled by two factors: particle rearrangement-induced dilation and particle crushing-induced contraction. The increase of permanent strain and the reduction of dilation were observed during cyclic loading and they tend to reach a stable state after a certain number of cycles. The crushing of aggregate is most significant in the first two cycles. The results also indicated that for the same axial strain the volumetric strain and the bound breakage in the cyclic loading tests are significantly larger than that in the monotonic loading tests,especially at high cyclic stress ratio.

关键词： DEM simulation granular materials Crushing Monotonic and Cyclic triaxial test