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Effect of blade geometry on the powder spreading process in additive manufacturing

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Particuology 2024年第11期94卷 345-355页

作者： Deze Yang xihua chu Qipeng Liu School of Civil Engineering Wuhan UniversityWuhan430072China Jiangxi Key Laboratory of Forming and Joining Technology for Aerospace Components Nanchang Hangkong UniversityNanchang330063China

In powder-bed-based additive manufacturing,the quality of the powder bed is closely related to the geometry of the blade used during the powder spreading *** this study,the spreading process with the vertical blade,inclined blade,and round blade with different radii was performed by discrete element method to investigate the effects of blade geometry on powder *** results show that at the same spreading parameters,the round blade caused the highest density than inclined blade and vertical *** the round blade radius can improve the packing density of the powder bed,but it has little effect on the *** increase in packing density is related to the transitional smoothness of the blade surface at the entrance of the powder *** smoother the shape transition of the blade surface at the powder bed entrance,the powders enter the powder bed more gently,so more powders enter the powder bed,resulting in higher packing *** results may provide suggestions for improving the laser melting process.

关键词： Additive manufacturing Powder spreading Blade geometry Discrete element method

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

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

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

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

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

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

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

Functionally Graded Cellular Structure Design Using the Subdomain Level Set Method with Local Volume Constraints

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Computer Modeling in Engineering & Sciences 2021年第9期128卷 1197-1218页

作者： Lianxiong Chen Hui Liu xihua chu Jiao Wang Department of Engineering Mechanics School of Civil EngineeringWuhan UniversityWuhan430072China State Key Laboratory for Structural Analysis of Industrial Equipment Dalian University of TechnologyDalian116024China School of Mechanics and Engineering Southwest Jiaotong UniversityChengdu611756China

Functional graded cellular structure(FGCS)usually shows superiormechanical behaviorwith lowdensity and high *** the development of additivemanufacturing,functional graded cellular structure gains its popularity in *** this paper,a novel approach for designing functionally graded cellular structure is proposed based on a subdomain parameterized level set method(PLSM)under local volume constraints(LVC).In this method,a subdomain level set function is defined,parameterized and updated on each subdomain independently making the proposed approach much faster and more ***,the microstructures on arbitrary two adjacent subdomains can be connected perfectly without any additional ***,the local volume constraint for each subdomain is applied by virtue of the augmented Lagrange multiplier ***,several numerical examples are given to verify the correctness and effectiveness of the proposed approach in designing the functionally graded cellular *** the optimized results,it is also found that the number of local volume constraints has little influence on the convergence speed of the developed approach.

关键词： Multiscale design hierarchical structure functionally graded cellular structure local volume constraints topology optimization