搜索到31686篇“ MICROSTRUCTURES“的相关文章
Molecular simulation study of the microstructures and properties of pyridinium ionic liquid[HPy][BF_(4)]mixed with acetonitrile
2025年
The microstructures and thermodynamic properties of mixed systems comprising pyridinium ionic liquid[HPy][BF_(4)]and acetonitrile at different mole fractions were studied using molecular dynamics simulation in this work.The following properties were determined:density,self-diffusion coefficient,excess molar volume,and radial distribution function.The results show that with an increase in the mole fraction of[HPy][BF_(4)],the self-diffusion coefficient decreases.Additionally,the excess molar volume initially decreases,reaches a minimum,and then increases.The rules of radial distribution functions(RDFs)of characteristic atoms are different.With increasing the mole fraction of[HPy][BF_(4)],the first peak of the RDFs of HA1-F decreases,while that of CT6-CT6 rises at first and then decreases.This indicates that the solvent molecules affect the polar and non-polar regions of[HPy][BF_(4)]differently.
XU Jian-QiangMA Zhao-PengCHENG SiLIU Zhi-CongZHU Guang-Lai
Finite Element Simulations on Failure Behaviors of Granular Materials with Microstructures Using a Micromechanics-Based Cosserat Elastoplastic Model
2024年
This paper presents a micromechanics-based Cosserat continuum model for microstructured granular materials.By utilizing this model,the macroscopic constitutive parameters of granular materials with different microstructures are expressed as sums of microstructural information.The 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 particles.Subsequently,the Cosserat elastoplastic model,along with its finite element formulation,is derived using the extended Drucker-Prager yield criteria.To investigate failure behaviors,numerical simulations of granular materials with different microstructures are conducted using the ABAQUS User Element(UEL)interface.It demonstrates the capacity of the proposed model to simulate the phenomena of strain-softening and strain localization.The study investigates the influence of microscopic parameters,including contact stiffness parameters and characteristic length,on the failure behaviors of granularmaterials withmicrostructures.Additionally,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 stage.Somemacroscopic parameters describing plasticity are shown to be partially related to microscopic factors such as confining pressure and size of the representative volume element.
Chenxi XiuXihua Chu
关键词:MICROMECHANICSMICROSTRUCTURES
Microstructures and micromechanical behaviors of high -entropy alloys investigated by synchrotron X-ray and neutron diffraction techniques: A review被引量:1
2024年
High-entropy alloys(HEAs)possess outstanding features such as corrosion resistance,irradiation resistance,and good mechan-ical properties.A few HEAs have found applications in the fields of aerospace and defense.Extensive studies on the deformation mech-anisms of HEAs can guide microstructure control and toughness design,which is vital for understanding and studying state-of-the-art structural materials.Synchrotron X-ray and neutron diffraction are necessary techniques for materials science research,especially for in situ coupling of physical/chemical fields and for resolving macro/microcrystallographic information on materials.Recently,several re-searchers have applied synchrotron X-ray and neutron diffraction methods to study the deformation mechanisms,phase transformations,stress behaviors,and in situ processes of HEAs,such as variable-temperature,high-pressure,and hydrogenation processes.In this review,the principles and development of synchrotron X-ray and neutron diffraction are presented,and their applications in the deformation mechanisms of HEAs are discussed.The factors that influence the deformation mechanisms of HEAs are also outlined.This review fo-cuses on the microstructures and micromechanical behaviors during tension/compression or creep/fatigue deformation and the application of synchrotron X-ray and neutron diffraction methods to the characterization of dislocations,stacking faults,twins,phases,and intergrain/interphase stress changes.Perspectives on future developments of synchrotron X-ray and neutron diffraction and on research directions on the deformation mechanisms of novel metals are discussed.
Yubo HuangNing XuHuaile LuYang RenShilei LiYandong Wang
关键词:MICROSTRUCTURES
Microstructures, Fabrics, and Seismic Properties of Mylonitic Amphibolites: Implications for Strain Localization in a Thickening Anisotropic Middle Crust of the North China Craton
2024年
Strain localization processes in the continental crust generate faults and ductile shear zones over a broad range of scales affecting the long-term lithosphere deformation and the mechanical response of faults during the seismic cycle.Seismic anisotropy originated within the continental crust can be applied to deduce the kinematics and structures within orogens and is widely attributed to regionally aligned minerals,e.g.,hornblende.However,naturally deformed rocks commonly show various structural layers(e.g.,strain localization layers).It is necessary to reveal how both varying amphibole contents and fabrics in the structural layers of strain localization impact seismic property and its interpretations in terms of deformation.We present microstructures,petrofabrics,and calculate seismic properties of deformed amphibolite with the microstructures ranging from mylonite to ultramylonite.The transition from mylonite to ultramylonite is accompanied by a slight decrease of amphibole grain size,a disintegration of amphibole and plagioclase aggregates,and amphibole aspect ratio increase(from 1.68 to 2.23),concomitant with the precipitation of feldspar and/or quartz between amphibole grains.The intensities of amphibole crystallographic preferred orientations(CPOs)show a progressively increasing trend from mylonitic layers to homogeneous ultramylonitic layers,as indicated by the JAm index increasing from 1.9–4.0 for the mylonitic layers and 4.0–4.8 for the transition layer,to 5.1–6.9 for the ultramylonitic layers.The CPO patterns are nearly random for plagioclase and quartz.Polycrystalline amphibole aggregates in the amphibolitic mylonite deform by diffusion,mechanical rotation,and weak dislocation creep,and develop CPOs collectively.The polymineralic matrix(such as quartz and plagioclase)of the mylonite and the ultramylonite deform dominantly by dissolution-precipitation,combined with weak dislocation creep.The mean P and S wave velocities are estimated to be 6.3 and 3.5 km/s,respectively,for three layers of the myl
Siqi LiuBo ZhangJinjiang ZhangJian ZhangLei GuoTao WangBaoyou HangXiaorong Li
关键词:MICROSTRUCTURES
微切削结构毛刺研究综述
2024年
随着微纳制造的快速发展,医疗、电子和能源等领域产品的微结构越来越复杂,精度要求也越来越高,而微结构在切削加工中易产生毛刺,极大地制约了产品的质量和性能。从切削微结构过程中毛刺的形成入手,论述了微结构毛刺形成机理的研究现状,介绍了微细毛刺尺寸的预测与表征方法。分析了切削参数、工艺规划、刀具设计和材料改性等因素对毛刺尺寸的影响,总结了毛刺的控制方法。对微细毛刺去除方法进行归纳分类,并综述了不同微结构毛刺的去除工艺及效果,探讨了目前微结构毛刺去除方面存在的瓶颈问题,指出了微结构毛刺去除方法的发展趋势。
雷雨许志龙徐西鹏高贾顺郭必成
关键词:微结构
Physical and mechanical properties and microstructures of submarine soils in the Yellow Sea被引量:1
2024年
In recent years,the exploration of seabed has been intensified,but the submarine soils of silt and sand in the Yellow Sea area have not been well investigated so far.In this study,the physical and mechanical properties of silt and sand from the Yellow Sea were measured using a direct shear apparatus and their microstructures were observed using a scanning electron microscope.The test results suggest that the shear strength of silt and sand increases linearly with the increase of normal stress.Based on the direct shear test,the scanning electron microscope was used to observe the section surface of sand.It is observed that the section surface becomes rough,with many“V”‐shaped cracks.Many particles appear on the surface of the silt structure and tend to be disintegrated.The X‐ray diffraction experiment reveals that the sand and silt have different compositions.The shear strength of sand is slightly greater than that of silt under high stress,which is related to the shape of soil particles and the mineral composition.These results can be a reference for further study of other soils in the Yellow Sea;meanwhile,they can serve as soil parameters for the stability and durability analyses of offshore infrastructure construction.
Zhuangcai TianYihua ChangSichao ChenGengchen WangYanhong HuChuan GuoLei JiaLei SongJianhua Yue
关键词:MICROSCOPE
Relationship between the unique microstructures and behaviors of high-entropy alloys被引量:2
2024年
High-entropy alloys(HEAs),which were introduced as a pioneering concept in 2004,have captured the keen interest of nu-merous researchers.Entropy,in this context,can be perceived as representing disorder and randomness.By contrast,elemental composi-tions within alloy systems occupy specific structural sites in space,a concept referred to as structure.In accordance with Shannon entropy,structure is analogous to information.Generally,the arrangement of atoms within a material,termed its structure,plays a pivotal role in dictating its properties.In addition to expanding the array of options for alloy composites,HEAs afford ample opportunities for diverse structural designs.The profound influence of distinct structural features on the exceptional behaviors of alloys is underscored by numer-ous examples.These features include remarkably high fracture strength with excellent ductility,antiballistic capability,exceptional radi-ation resistance,and corrosion resistance.In this paper,we delve into various unique material structures and properties while elucidating the intricate relationship between structure and performance.
Yaqi WuPeter KLiawRuixuan LiWeiran ZhangGuihong GengXuehui YanGuiqun LiuYong Zhang
干燥方法对山芋全粉微观结构和品质的影响
2024年
以新鲜山芋及经熟化的山芋为原料,分别采用热风干燥(Hot air drying,HAD)、远红外干燥(Far infrared drying,FID)、真空冷冻干燥(Vacuum freeze drying,VFD)、真空干燥(Vacuum drying,VD)法制备山芋生、熟全粉,比较各干燥方式得到的山芋全粉微观结构,并利用主成分分析法评价山芋全粉品质。结果表明,HAD和FID制备的山芋全粉颗粒表面凹凸不平,有许多裂纹和孔洞;VFD和VD制备的山芋全粉微观结构保持度较好,表面结构较光滑,表面附着的小颗粒也较少。经熟化处理后,山芋粉体颗粒体积膨胀,折叠起皱。VFD制备的山芋全粉亮度较大且色泽较白,持水性、持油性、复水能力较佳,总酚和VC含量最高。根据主成分分析法得到综合评分,其中,VFD山芋生粉得分最高,品质最好。综上,不同干燥方法对山芋全粉的微观结构和品质有较大影响,要综合考虑生产需求和成本来选择制备山芋全粉的最佳方法。
杨柳青谭琳玉朱荣安葛远飞杨红王储炎
关键词:微观结构
氯化钾水溶液微观结构的分子动力学模拟研究被引量:1
2024年
氯化钾水溶液不同于氯化钠的,其在低温下只能形成无水盐和冰.现有研究表明在氯化钠水溶液中不仅存在着水分子连续分布的区域与离子团簇,而且这二者的物质组成也与该溶液所形成晶体的分别对应.为了探寻其他溶液中是否存在此类对应关系,并考察溶液的微观结构,本文采用分子动力学方法对氯化钾水溶液进行了研究,表明了该溶液的一些性质.氯化钾水溶液中K+-K+和Cl--Cl-径向分布函数的特征具有一致性,峰的最大值所对应的位置都分别相同,明显不同于氯化钠水溶液的.系列时刻下瞬态图像内O到其最近离子距离中最大值的统计结果表明氯化钾水溶液中存在着一定大小的水分子连续分布的区域,其平均尺寸至少为2.26 nm;瞬态图像中K+与其最近邻Cl-之间的距离主要分布在0.28 nm~0.38 nm之间,占比约为97.4%;溶液中存在着较大和较小两类离子团簇,较大团簇的平均尺寸为1.73nm,平均离子数是25.0,其内部的离子与周围离子之间具有与氯化钾晶体类似的结构;这些结果表明氯化钾水溶液中也具有微观不均匀性和自聚集效应.将离子间径向分布函数上各峰最大值所对应距离之间的关系与氯化钾晶体中各离子之间距离的几何关系进行对比,并结合离子瞬态图像,给出了离子径向分布函数上各峰的来源,但明显不同于氯化钠水溶液中的情况.另外,通过对比与分析解释了氯化钾水溶液中离子对和团簇形成的原因,并表明原子和离子间相互作用对溶液的微观不均匀具有重要影响.结果还表明氯化钾水溶液中水分子连续分布区域以及离子团簇的物质组成分别与其所形成的冰和氯化钾晶体的组成具有一致性,而且离子团簇的结构和氯化钾晶体的也类似.再结合氯化钠水溶液的结果,表明溶液中存在着与其所能够形成晶体组成类似的对应单元,这为理解溶液中晶体的形成提供了启发.
王丽娜张文惠尚洁莹赵兴宇周恒为
关键词:离子团簇分子动力学
Tuning microstructures of TC4 ELI to improve explosion resistance
2024年
A reasonable heat treatment process for TC4 ELI titanium alloy is crucial to tune microstructures to improve its explosion resistance.However,there is limited investigation on tuning microstructures of TC4 ELI to improve explosion resistance.Moreover,the current challenge is quantifying microstructural changes'effects on explosion resistance and incorporating microstructural changes into finite element models.This work aims to tune microstructures to improve explosion resistance and elucidate their anti-explosion mechanism,and find a suitable method to incorporate microstructural changes into finite element models.In this work,we systematically study the deformation and failure characteristics of TC4 ELI plates with varying microstructures using an air explosion test and LS-DYNA finite element modeling.The Johnson-Cook(JC)constitutive parameters are used to quantify the effects of microstructural changes on explosion resistance and incorporate microstructural changes into finite element models.Because of the heat treatment,one plate has equiaxed microstructure and the other has bimodal microstructure.The convex of the plate after the explosion has a quadratic relationship with the charge mass,and the simulation results demonstrate high reliability,with the error less than 17.5%.Therefore,it is feasible to obtain corresponding JC constitutive parameters based on the differences in microstructures and mechanical properties and characterize the effects of microstructural changes on explosion resistance.The bimodal target exhibits excellent deformation resistance.The response of bimodal microstructure to the shock wave may be more intense under explosive loading.The well-coordinated structure of the bimodal target enhances its resistance to deformation.
Changle ZhangYangwei WangLin WangZixuan NingGuoju LiDongping ChenZhi-Wei YanYuchen SongXucai Wang
关键词:MICROSTRUCTURE

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