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Particuology 2018年第1期16卷 106-113页

作者： Shaocheng Di Yanzhuo Xue Xiaolong Bai Qing wang College of Shipbuilding Engineering Harbin Engineering University Harbin 150001 China

We investigated the effects of model size and particle size on the simulated macroscopic mechanical properties, uniaxial compressive strength, Young＇s modulus, and flexural strength of sea-ice samples, using the discrete-element method （DEM） with a bonded-particle model. Many different samples with a hexagonal-close-packing pattern and a unique particle size were considered, and several ratios of particle size to sample dimension （D/L） were studied for each sample. The macroscopic mechanical properties simulated by the DEM decrease monotonously with an increase in D/L. For different samples with different particle sizes, the macroscopic mechanical properties will be identical when D/L is constant. The quanti- tative relationships between macroscopic mechanical properties and ratio of particle size to sample size are important aspects in engineering applications of the DEM method. The results provide guidance on the choice of a particle size in the DEM simulation for numerical samples with a hexagonal-close-packing pattern.

关键词： Discrete-element method Bonded-particle model Sample size Particle size size effect

PARTICULATE size effectS IN THE PARTICLE-REINFORCED METAL-MATRIX COMPOSITES

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Acta Mechanica Sinica 2001年第1期17卷 45-58页

作者：魏悦广 LNM Institute of Mechanics Chinese Academy of Sciences Beijing China 100080

The influences of I,article size on the mechanical properties of the particulate metal matrix composite;are obviously displayed in the experimental observations. However, the phenomenon can not be predicted directly using the conventional elastic-plastic theory. It is because that no length scale parameters are involved in the conventional theory. In the present research, using the strain gradient plasticity theory, a systematic research of the particle size effect in the particulate metal matrix composite is carried out. The roles of many composite factors, such as: the particle size, the Young's modulus of the particle, the particle aspect ratio and volume fraction, as well as the plastic strain hardening exponent of the matrix material, are studied in detail. In order to obtain a general understanding for the composite behavior, two kinds of particle shapes, ellipsoid and cylinder, are considered to check the strength dependence of the smooth or non-smooth particle surface. Finally, the prediction results will be applied to the several experiments about the ceramic particle-reinforced metal-matrix composites. The material length scale parameter is predicted.

关键词： size effect strain gradient plasticity the particle-reinforced metal-matrix composite

An insight into aggregation kinetics of polystyrene nanoplastics interaction with metal cations

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Chinese Chemical Letters 2022年第12期33卷 5213-5217页

作者： Yucheng Zhang Xiaotong Su Nora FYTam Xiaolan Lao Meiling Zhong Qihang Wu Huifang Lei Zihui Chen Zhang Li Jie Fu Key Laboratory for Water Quality and Conservation of the Pearl Stream Delta Ministry of EducationSchool of Environmental Science and EngineeringGuangzhou UniversityGuangzhou 510006China State Key Laboratory of Marine Pollution and Department of Chemistry City University of Hong KongHong KongChina School of Science and Technology Open University of Hong KongHong KongChina School of Environmental Science and Engineering Huazhong University of Science and TechnologyWuhan 430074China

Once inevitably released into the aquatic environment,polystyrene nanoplastics(PS-NPs)will present complicated environmental behaviors,of which the aggregation is a key process determining their environmental fate and impact.In this study,the aggregation kinetics of different sizes(30 nm and 100 nm)of PS-NPs with metal cations(Na^(+),K^(+),Ca^(2+),Mg^(2+)and Pb^(2+))at different solution pH(3,6 and 8)were investigated.The results showed that the aggregation of PS-NPs increased with cation concentration.Taking Pb^(2+)as an example,the adsorption behavior of cations onto PS-NPs was determined by transmission electron microscopy(TEM)and energy dispersive X-ray(EDX)spectroscopy,which demonstrated Pb^(2+)could be adhered onto the surface of PS-NPs with the effect of charge neutralization.The critical coagulation concentrations(CCC)of smaller PS-NPs were higher than that of larger PS-NPs for monovalent cations,whereas a different pattern is observed for divalent cations.It was suggested that there were other factors that DLVO theory does not consider affect the stability of NPs with different particle sizes.In addition,it should be noted that PS-NPs had the capacity of adsorbing large amounts of heavy metal cations and carried them transport to a long distance,and the corresponding ecological risks need to further elucidate.

关键词： Polystyrene nanoplastics Lead cation Aggregation kinetics Critical coagulation concentration size effect

Stability and regeneration of metal catalytic sites with different sizes in Fenton-like system

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中国化学快报:英文版 2023年第8期34卷 142-146页

作者： Yanan Shang Yujiao Kan Xing Xu School of Safety and Environmental Engineering Shandong University of Science and TechnologyQingdao 266590China School of Environmental Science and Engineering Shandong UniversityQingdao 266237China

Metal-based catalysts with different site sizes(e.g.,metal nanoparticles(NPs)and single atom catalysts(SACs))demonstrated outstanding catalytic activities in versatile Fenton-like reactions.However,the surface/structural instability is a critical issue,which will result in rapid passivation in Fenton-like reaction and fail in long-term operation.The catalytic stability of the catalysts with different metal sizes considering versatile peroxides(H_(2)O_(2),peroxymonosulfate(PMS),and peroxodisulfate(PDS))should be analyzed.In addition,strategies for catalyst regeneration and recyclability improvement are also important to realize the metal-based catalysts for practical applications.In this review,catalytic stability of catalysts with different metal sizes in the backgrounds of versatile peroxides and water matrixes in Fenton-like reactions were first evaluated.Regeneration of metal catalytic sites with different methods were also reviewed.Finally,major challenges and development of methods concerning the stability and regeneration of metal catalytic sites with different sizes were discussed to understand the future researches of metal catalytic sites in Fenton-like reactions.

关键词： size effect Metal nanoparticles catalysts Single atom catalysts Fenton-like

size-dependent thermoelasticity of a finite bi-layered nanoscale plate based on nonlocal dual-phase-lag heat conduction and Eringen's nonlocal elasticity

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Applied Mathematics and Mechanics(English Edition) 2021年第1期42卷 1-16页

作者： Zhangna XUE Gongqi CAO Jianlin LIU College of Pipeline and Civil Engineering China University of Petroleum(East China)Qingdao 266580Shandong ProvinceChina

The size effects on heat conduction and elastic deformation are becoming significant along with the miniaturization of the device and wide application of ultrafast lasers.In this work,to better describe the transient responses of nanostructures,a size-dependent thermoelastic model is established based on nonlocal dual-phase-lag(N-DPL)heat conduction and Eringen's nonlocal elasticity,which is applied to the one-dimensional analysis of a finite bi-layered nanoscale plate under a sudden thermal shock.In the numerical part,a semi-analytical solution is obtained by using the Laplace transform method,upon which the effects of size-dependent characteristic lengths and material properties of each layer on the transient responses are discussed systematically.The results show that the introduction of the elastic nonlocal parameter of Medium 1 reduces the displacement and compressive stress,while the thermal nonlocal parameter of Medium 1 increases the deformation and compressive stress.These findings may be beneficial to the design of nano-sized and multi-layered devices.

关键词： thermoelasticity size effect multi-layered nanostructure

The metastable constituent effects on size-dependent deformation behavior of nanolaminated micropillars: Cu/FeCoCrNi vs Cu/CuZr

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Journal of Materials Science & Technology 2021年第9期68卷 16-29页

作者： Yufang Zhao Jinyu Zhang YaQiang Wang Shenghua Wu Xiaoqing Liang Kai Wu Gang Liu Jun Sun State Key Laboratory for Mechanical Behavior of Materials Xi'an Jiaotong UniversityXi'an710049China

Metastable high entropy alloys(HEAs) and amorphous metallic glasses(MGs), with the chemical disordered character, are intensively studied due to their excellent performance. Here, we introduce Cu to separately constrain these two metastable materials and comparatively investigate their deformation behaviors and mechanical properties of Cu/HEA Fe Co Cr Ni and Cu/MG Cu Zr nanolaminated micropillars in terms of intrinsic layer thickness h and extrinsic pillar diameter D. The metastable HEA layers, as the hard phase in Cu/HEA micropillars, are stable and dominate the deformation, while transformation(crystallization) occurs in MG which plays a minor role in deformation of Cu/MG micropillars. The h-controlled deformation mode transits from the D-independent homogenous-like deformation at large h to the Ddependent shear banding at small h in both Cu/HEA and Cu/MG micropillars. Although both Cu/HEA and Cu/MG micropillars exhibit a maximum strain hardening capability controlled by h, the former manifests much lower hardening capability compared with the latter. The intrinsic size h and extrinsic size D have a strong coupling effect on the strength of Cu/HEA and Cu/MG micropillars. The strength of strength of Cu/HEA micropillars exhibits the D-dependent transition from "smaller is stronger" to "smaller is weaker"with increasing h. By contrast, the strength of Cu/MG micropillars exhibits the transition from bulk-like D-independent behavior at large h to small volume D-dependent behavior(smaller is stronger) at small h.

关键词： High-entropy alloys Metallic glasses Nanolaminated micropillars size effect

Growing actin networks regulated by obstacle size and shape

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Acta Mechanica Sinica 2017年第2期33卷 222-233页

作者： Bo Gong Ji Lin Jin Qian Department of Engineering Mechanics Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Zhejiang University Hangzhou 310027 China

Growing actin networks provide the driving force for the motility of cells and intracellular pathogens. Based on the molecular-level processes of actin polymerization, branching, capping, and depolymerization, we have developed a modeling framework to simulate the stochastic and cooperative behaviors of growing actin networks in propelling obstacles, with an emphasis on the size and shape effects on work capacity and filament orientation in the growing process. Our results show that the characteristic size of obstacles changes the protrusion power per unit length, without influencing the orientation distribution of actin filaments in growing networks. In contrast, the geometry of obstacles has a profound effect on filament patterning, which influences the orientation of filaments differently when the drag coefficient of environment is small, intermediate, or large. We also discuss the role of various parameters, such as the aspect ratio of obstacles, branching rate, and capping rate, in affecting the protrusion power of network growth.

关键词： Actin network Growth dynamics Monte Carlo simulation size effect Shape effect

size and temperature effects on band gaps in periodic fluid-filled micropipes

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Applied Mathematics and Mechanics(English Edition) 2021年第9期42卷 1219-1232页

作者： Jun HONG Zhuangzhuang HE Gongye ZHANG Changwen MI Jiangsu Key Laboratory of Engineering Mechanics School of Civil EngineeringSoutheast UniversityNanjing 210096China

A new model is proposed for determining the band gaps of flexural wave propagation in periodic fluid-filled micropipes with circular and square thin-wall cross-sectional shapes, which incorporates temperature, microstructure, and surface energy effects. The band gaps depend on the thin-wall cross-sectional shape, the microstructure and surface elastic material constants, the pipe wall thickness, the unit cell length, the volume fraction, the fluid velocity in the pipe, the temperature change,and the thermal expansion coefficient. A systematic parametric study is conducted to quantitatively illustrate these factors. The numerical results show that the band gap frequencies of the current non-classical model with both circular and square thin-wall cross-sectional shapes are always higher than those of the classical model. In addition,the band gap size and frequency decrease with the increase of the unit cell length according to all the cases. Moreover, the large band gaps can be obtained by tailoring these factors.

关键词： band gap couple stress surface energy size effect conveying fluid thermal load

Numerical Investigation of the Cushion and size effects During Single-Particle Crushing via DEM

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Acta Mechanica Solida Sinica 2020年第6期33卷 851-863页

作者： Du-min Kuang Zhi-lin Long Rui-qi Guo Piao-yi Yu Xu-tong Zhou Jie Wang College of Civil Engineering and Mechanics Xiangtan UniversityXiangtan 411105China

This paper uses the discrete element method to model the size and cushion effects during single-particle crushing tests.We propose simplified numerical modeling to examine the effects of particle size and coordination number on particle breakage behavior.We validate the proposed modeling by comparing the numerical results with the experimental data reported in the literature,in terms of the variability of particle tensile strength and axial force-displacement responses.Based on the numerical results,it is clear that a larger particle size entails a higher tensile strength with a larger discreteness.In addition,the characteristic tensile strength increases linearly with an increasing coordination number.Moreover,smaller particles are more susceptible to the cushion effect than larger particles.The numerical results also indicate that an increasing coordination number induces a more ductile mode of failure.Based on these results,we propose an empirical equation for calculating tensile strength,incorporating both the cushion effect and the size effect.

关键词： Particle breakage Cushion effect size effect Discrete element method

Coupling effects of void size and void shape on the growth of prolate ellipsoidal microvoid

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Acta Mechanica Sinica 2005年第3期21卷 272-277页

作者： Minsheng Huang Zhenhuan Li Cheng Wang Department of Mechanics Huazhong University of Science & Technology Wuhan 430074 China

The combined effects of void size and void shape on the void growth are studied by using the classical spectrum method. An infinite solid containing an isolated prolate spheroidal void is considered to depict the void shape effect and the Fleck-Hutchinson phenomenological strain gradient plasticity theory is employed to capture the size effects. It is found that the combined effects of void size and void shape are mainly controlled by the remote stress triaxiality. Based on this, a new size-dependent void growth model similar to the Rice-Tracey model is proposed and an important conclusion about the size-dependent void growth is drawn： the growth rate of the void with radius smaller than a critical radius rc may be ignored. It is interesting that rc. is a material constant independent of the initial void shape and the remote stress triaxiality.

关键词： Void shape size effect Strain gradient Stress triaxiality Microvoid