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Finite Element Simulations on Failure Behaviors of Granular Materials with Microstructures Using a Micromechanics-Based Cosserat Elastoplastic Model

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Computer Modeling in Engineering & Sciences 2024年第3期138卷 2305-2338页

作者： Chenxi Xiu xihua chu School of Civil Engineering Chongqing Jiaotong UniversityChongqing400074China School of Civil Engineering Wuhan UniversityWuhan430072China

This paper presents a micromechanics-based Cosserat continuum model for microstructured granular *** utilizing this model,the macroscopic constitutive parameters of granular materials with different microstructures are expressed as sums of microstructural *** microstructures under consideration can be classified into three categories:a medium-dense microstructure,a dense microstructure consisting of one-sized particles,and a dense microstructure consisting of two-sized ***,the Cosserat elastoplastic model,along with its finite element formulation,is derived using the extended Drucker-Prager yield *** investigate failure behaviors,numerical simulations of granular materials with different microstructures are conducted using the ABAQUS User Element(UEL)*** demonstrates the capacity of the proposed model to simulate the phenomena of strain-softening and strain *** study investigates the influence of microscopic parameters,including contact stiffness parameters and characteristic length,on the failure behaviors of granularmaterials ***,the study examines themesh independence of the presented model and establishes its relationship with the characteristic length.A comparison is made between finite element simulations and discrete element simulations for a medium-dense microstructure,revealing a good agreement in results during the elastic *** parameters describing plasticity are shown to be partially related to microscopic factors such as confining pressure and size of the representative volume element.

关键词： Granular materials micromechanics Cosserat elastoplastic model microstructures failure behaviors

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基于人工神经网络的颗粒材料本构关系及边值问题研究

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应用数学和力学 2024年第2期45卷 155-166页

作者：张广江杨德泽楚锡华武汉大学工程力学系武汉430072

颗粒材料被广泛运用于工程实践中,通过数值模拟解决颗粒材料有关的边值问题,对于指导工程实践具有重要意义.通过应用人工神经网络算法,将基于离散颗粒模型的离散单元法与基于连续介质模型的有限单元法有机结合以求解颗粒材料边值问题,... 详细信息

颗粒材料被广泛运用于工程实践中,通过数值模拟解决颗粒材料有关的边值问题,对于指导工程实践具有重要意义.通过应用人工神经网络算法,将基于离散颗粒模型的离散单元法与基于连续介质模型的有限单元法有机结合以求解颗粒材料边值问题,形成了一套新的、完整的模型及解决方案,即细观模型离线计算的细-宏观两尺度模型及求解系统.具体为:先基于离散单元法获取颗粒材料的主应力、主应变以及对应的应力-应变矩阵等数据;再将获取的数据利用人工神经网络算法构建在主空间上描述颗粒材料本构关系的人工神经网络模型;最后,通过用户自定义材料子程序UMAT将人工神经网络模型导入ABAQUS中求解颗粒材料边值问题.通过平板受压以及边坡稳定性数值试验,并与经典弹塑性模型求解结果进行对比,表明了训练后的人工神经网络模型能够有效地反映颗粒材料的本构关系,并能够运用于实践求解边值问题,验证了该求解方案的可行性.

关键词：颗粒材料人工神经网络离散元法有限元法边值问题

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Validation of an improved two-fluid model with particle rotation for gas-solid fluidized bed

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Particuology 2023年第10期81卷 149-161页

作者： Lian Wang xihua chu School of Civil Engineering Wuhan UniversityWuhan430072HubeiChina

Gas-solid fluidized beds are widely applied in chemical and process *** is of significance to establish a reasonable and effective mathematical model to explore the hydrodynamics of gas-particle system for industrial *** a less computationally demanding alternative to the discrete descriptions,two-fluid model considering kinetic theory of granular flow is often adopted to describe the fluidized behaviors of particles,but it cannot characterize the rotation of particles and its influence on the fluidized *** this study,to address the rotation effect of the fluidized particles,a two-fluid model combining the classical fluid and micropolar fluid is established,namely *** the CMTFM,classical fluid is used to describe the motion of gas phase,while micropolar fluid is adopted to describe the motion of particle phase,and the rotation of particles and its influence on the hydrodynamics of the gas-particle system are characterized by the degree of freedom of microrotation and the improved drag force based on micropolar *** the calculation of the gas-solid bubbling fluidized bed,we investigated the influence of the microstructure parameters,particle-particle collision restitution coefficient and inlet velocity,and the results are compared to those from TFM model and *** the analysis,it manifests that pressure drop and expansion height of the fluidized bed under the consideration of the microrotation effect are closer to the experiments,which demonstrates the feasibility and advantage of the classical-micropolar two-fluid model.

关键词： Gas-solid fluidized bed Two-fluid model Micropolar fluid Microstructure parameter Fluidized behaviors

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基于离散元法的SLM刮刀倾角对粉末铺展行为的影响研究

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力学学报 2024年第3期56卷 774-784页

作者：李雯刘其鹏高月华楚锡华张昭王振军南昌航空大学江西省航空构件成形与连接重点实验室南昌330063 武汉大学土木工程学院武汉430072 大连理工大学工程力学系辽宁大连116024

刮刀倾角对选区激光熔化过程粉末铺展行为有重要影响.基于离散元法建立铺粉数值模型,对不同刮刀倾角的铺粉过程及粉层质量进行模拟研究.针对不同的刮刀倾角,提出一个量化指标对粉层铺展的致密度和均匀性进行综合评估,获得刮刀倾角对粉... 详细信息

刮刀倾角对选区激光熔化过程粉末铺展行为有重要影响.基于离散元法建立铺粉数值模型,对不同刮刀倾角的铺粉过程及粉层质量进行模拟研究.针对不同的刮刀倾角,提出一个量化指标对粉层铺展的致密度和均匀性进行综合评估,获得刮刀倾角对粉层质量的影响规律.根据颗粒分布及运动特征将粉堆颗粒体系划分为底层区、斜坡区、刮刀影响区和内部区4个区域.针对各区域进行铺粉过程动力学机理的深入研究,包括颗粒运动轨迹和速度场、刮刀前方剪切带、颗粒间力链分布及演化等.研究发现:刮刀倾角小于0时,颗粒体系难以形成完整的环流运动,剪切带较小,流向沉积层的颗粒较少,颗粒间强力链较少,刮刀间隙前方易形成力拱导致颗粒堵塞,进而形成空斑使得沉积层的致密度和均匀性较低.刮刀倾角大于0时,颗粒体系的环流运动较充分,剪切带较大,流向沉积层的颗粒增多,随倾角增大强力链增多,刮刀压实作用增强,有利于沉积层致密度和均匀性的提高.本研究为优化工艺参数、提高粉层沉积质量提供了理论基础.

关键词：选区激光熔化离散单元法铺粉过程刮刀倾角流动机理

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The Effects of the Particle Size Ratio on the Behaviors of Binary Granular Materials

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Computer Modeling in Engineering & Sciences 2023年第7期136卷 63-85页

作者： Deze Yang xihua chu School of Civil Engineering Wuhan UniversityWuhan430072China

The particle size ratio(PSR)is an important parameter for binary granular materials,which may aect the microstructure and macro behaviors of granular ***,the eect of particle ratio on granular assemblies with dierent arrangements is still *** explore and further clarify the eect of PSR in dierent packing structures,three types of numerical samples with regular,layered,and random packing are *** results show that PSR has signi􀀀cant eects on binary granular samples with regular *** larger the PSR,the stronger the strength,the larger the modulus,and the smaller the angle between the shear band and the load *** a theoretical solution of the peak stress ratio *** is obtained for regular packing,and the results by DEM are in good agreement with the theoretical *** layered packing,PSR has little eect on peak stress ratio due to similar microstructure obtained with the changing of *** modulus slightly increased with the increase of *** random packing with small grain content of 50%,PSR has little eect in the range of 0.5–0.9,but in a larger range,larger PSR leads to greater modulus.

关键词： Discrete element method binary granular materials particle size ratio packing

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Peridynamic Modeling and Simulation of Fracture Process in Fiber-Reinforced Concrete

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Computer Modeling in Engineering & Sciences 2021年第4期127卷 241-272页

作者： Zhuang Chen xihua chu School of Civil Engineering Wuhan UniversityWuhan430072China State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of TechnologyDalian116023China

In this study,a peridynamic fiber-reinforced concrete model is developed based on the bond-based peridynamic model with rotation effect(BBPDR).The fibers are modelled by a semi-discrete method and distributed with random locations and angles in the concrete specimen,since the fiber content is low,and its scale is smaller than the concrete *** interactions between fibers and concrete matrix are investigated by the improvement of the bond’s strength and ***,the frictional effect between the fibers and the concrete matrix is considered,which is divided into static friction and slip *** validate the proposed model,several examples are simulated,including the tensile test and the three-point bending beam *** the numerical results of the proposed model are compared with the experiments and other numerical *** comparisons show that the proposed model is capable of simulating the fracture behavior of the fiber-reinforced *** adding the fibers,the tensile strength,bending strength,and toughness of the fiber-reinforced concrete specimens are ***,the fibers distribution has an impact on the crack path,especially in the three-point bending beam test.

关键词： Peridynamics fiber-reinforced concrete fracture mechanics numerical simulation three-point bending beam

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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

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Parameterized level set method for structural topology optimization based on the Cosserat elasticity

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Acta Mechanica Sinica 2021年第4期37卷 620-630,I0002页

作者： Lianxiong Chen Ji Wan xihua chu Hui Liu Department of Engineering Mechanics School of Civil EngineeringWuhan UniversityWuhan 430072China

When describing the mechanical behavior of some engineering materials,such as composites,grains,biological materials and cellular solids,the Cosserat continuum theory has more powerful capabilities compared with the classical Cauchy elasticity since an additional local rotation of point and its counterpart(couple stress)are considered in the Cosserat elasticity to represent the material microscale *** this paper,a parameterized level set topology optimization method is developed based on the Cosserat elasticity for the minimum compliance problem of the Cosserat *** influence of material characteristic length and Cosserat shear modulus on the optimized structure is investigated in *** can be found that the microstructural constants in the Cosserat elasticity have a significant impact on the optimized topology *** addition,the minimum feature size and the geometric complexity of the optimized structure can be controlled implicitly by adjusting the parameters of the characteristic length and Cosserat shear modulus ***,the optimized structure obtained by the developed Cosserat elasticity based parameterized level set method will degenerate to the result by using the classical Cauchy elasticity based parameterized level set method when the Cosserat shear modulus approaches zero.

关键词： Structural topology optimization Cosserat continuum theory Parameterized level set method Cosserat elasticity Scale effect

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The Material Deformation and Internal Structure Development of Granular Materials under Different Cyclic Loadings

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Computer Modeling in Engineering & Sciences 2022年第2期130卷 653-670页

作者： Jiao Wang xihua chu Jinbao Wang School of Mechanics and Engineering Southwest Jiaotong UniversityChengdu610031China Department of Engineering Mechanics Wuhan UniversityWuhan430072China School of Marine Engineering Equipment Zhejiang Ocean UniversityZhoushan326022 China

Common structures in engineering such as slopes,roadbeds,ballasts,etc.,are closely related to granular *** are usually subjected to long-term cyclic *** study mainly focused on the mechanical behaviors of randomly arranged granular materials before they reach a stable state under different cyclic *** variation of the maximum axial strain and the influence of CSR(cyclic stress ratio)were *** energy consumed in each cycle under constant confining stress loading condition is significantly greater than that of the fixed wall loading *** internal deformation evolution of granular materials is studied in *** deformation mode of granular material under cyclic loading at different positions inside the material is different according to the strain *** addition,the strain,force chain structure and contact force magnitude are combined to explore their effects on local deformation of granular materials under cyclic *** the perspective of the deformation form,the material sample can be divided into several regions,and the ability to adjust particle positions determines the deformation mode of different *** changes of local strain with the cyclic loading also reflect the contribution of particle displacements to the evolution *** research will provide insights into the understanding of granular materials behaviors under cyclic loading.

关键词： Granular material DEM cyclic loading mesostructured force chain

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Improved method for zero-energy mode suppression in peridynamic correspondence model

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Acta Mechanica Sinica 2019年第5期35卷 1021-1032页

作者： Ji Wan Zhuang Chen xihua chu Hui Liu Department of Engineering Mechanics Wuhan UniversityWuhan 430072China

The peridynamic correspondence model provides a general formulation to incorporate the classical local model and,therefore,helps to solve mechanical problems with discontinuities *** it suffers from zero-energy mode instability in numerical implementation due to the approximation of deformation gradient *** suppress zero-energy modes,previous stabilized methods were generally more based on adding a supplemental force state derived from bond-based peridynamic theory,which requires a bond-based peridynamic *** this work,we present an improved stabilized method where the stabilization force state is derived directly from the peridynamic correspondence ***,the bond-based peridynamic micro-modulus is *** improved method needs no extra constant to control the magnitude of stabilization force state and it is suitable for either isotropic or anisotropic *** examples are presented to demonstrate its performance in simulating crack propagation,and numerical results show its efficiency and effectiveness.

关键词： Peridynamic correspondence model Zero-energy modes Anisotropic material Damage

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