Articoli di riviste: "Particle packing"

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Wiącek, Joanna, Mateusz Stasiak e Jalal Kafashan. "Structural and Micromechanical Properties of Ternary Granular Packings: Effect of Particle Size Ratio and Number Fraction of Particle Size Classes". Materials 13, n. 2 (11 gennaio 2020): 339. http://dx.doi.org/10.3390/ma13020339.

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The confined uniaxial tests of packings with discrete particle size distribution (PSD) were modeled with the discrete element method. Ternary packings of spheres with PSD uniform or nonuniform by number of particles were examined in three-dimensional (3D) system. The study addressed an effect of the particle size ratio and the particle size fraction on structural and micromechanical properties of mixtures. A study of packing structure included porosity and coordination numbers, while the investigation of micromechanical properties included distribution of normal contact forces and stress transmission through the packing. A micro-scale investigation of the effect of particle size ratio on structure and mechanics of the ternary packings revealed a strong relationship between the properties of sample and the value of parameter till its critical value was reached. A further increase in particle size ratio did not significantly affect properties of packings. Contrary to the porosity and coordination numbers, the partial stresses were highly affected by the fraction of particle size classes in ternary mixtures. The contribution of the partial stress into the global stress was determined by number fraction of particles in packings with small particle size ratio, while it was mainly determined by particle size ratio in packings with small particle size ratio.

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Miao, Yinghao, Xin Liu, Yue Hou, Juan Li, Jiaqi Wu e Linbing Wang. "Packing Characteristics of Aggregate with Consideration of Particle size and Morphology". Applied Sciences 9, n. 5 (28 febbraio 2019): 869. http://dx.doi.org/10.3390/app9050869.

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The packing characteristics of aggregates are very important for aggregate blend design, which is closely related to the performance of mixtures. In this study, an indoor packing experiment was designed to investigate the behaviors of single-size particle packing and two-size particle packing. The effects of particle composition, particle size and size ratio, particle morphology on packing characteristics were also evaluated. Two kinds of aggregates (crushed stone and gravel) with significant morphological differences were selected for the test. The angularity of the aggregates was quantitatively analyzed using the variance of mean curvature ( S C m 2 ) of particle surface in accordance with the 3-D scanning measurements. Based on the test results, the packing characteristics of aggregates were analyzed using the air void content (Va) and the packing function index (Ipf) proposed in this paper. It is shown that the analysis results of packed ideal spheres cannot be directly used to describe the packing characteristics of aggregates. Particle morphology has a significant impact on packing characteristics, especially on the Va. The Va of packed aggregates with poor angularity is significantly smaller than that with good angularity. Ipf can be used to quantitatively distinguish the packing function of particles. The test results show that the packing function of particles cannot be simply divided into the skeleton building and air voids filling. Generally, the particles in packed blend have both of these functions. The packing function of particles depends not only on the particle size, but also on the composition of particles with different size. When the size ratio and volume ratio are the same, the packing characteristics of the two-size particle blends will still change with the change of the particle size. The exploration of packing behaviors of single- size and two- size particle aggregates is helpful for analyzing the packing behaviors of blends with multi-size particles.

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Zhao, Tingting, Y. T. Feng e Yuanqiang Tan. "Characterising 3D spherical packings by principal component analysis". Engineering Computations 37, n. 3 (21 novembre 2019): 1023–41. http://dx.doi.org/10.1108/ec-05-2019-0225.

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Purpose The purpose of this paper is to extend the previous study [Computer Methods in Applied Mechanics and Engineering 340: 70-89, 2018] on the development of a novel packing characterising system based on principal component analysis (PCA) to quantitatively reveal some fundamental features of spherical particle packings in three-dimensional. Design/methodology/approach Gaussian quadrature is adopted to obtain the volume matrix representation of a particle packing. Then, the digitalised image of the packing is obtained by converting cross-sectional images along one direction to column vectors of the packing image. Both a principal variance (PV) function and a dissimilarity coefficient (DC) are proposed to characterise differences between different packings (or images). Findings Differences between two packings with different packing features can be revealed by the PVs and DC. Furthermore, the values of PV and DC can indicate different levels of effects on packing caused by configuration randomness, particle distribution, packing density and particle size distribution. The uniformity and isotropy of a packing can also be investigated by this PCA based approach. Originality/value Develop an alternative novel approach to quantitatively characterise sphere packings, particularly their differences.

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Amano, Yuto, Takashi Itoh, Hoshiaki Terao e Naoyuki Kanetake. "Prediction of Packing Density of Milled Powder Based on Packing Simulation and Particle Shape Analysis". Materials Science Forum 534-536 (gennaio 2007): 1621–24. http://dx.doi.org/10.4028/www.scientific.net/msf.534-536.1621.

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For precise property control of sintered products, it is important to know the powder characteristics, especially the packing density of the powder. In a previous work, we developed a packing simulation program that could make a packed bed of spherical particles having particle size distribution. In order to predict the packing density of the actual powder that consisted of nonspherical particles, we combined the packing simulation with a particle shape analysis. We investigated the influence of the particle size distribution of the powder on the packing density by executing the packing simulation based on particle size distributions of the actual milled chromium powders. In addition, the influence of the particle shape of the actual powder on the packing density was quantitatively analyzed. A prediction of the packing density of the milled powder was attempted with an analytical expression between the particle shape of the powder and the packing simulation. The predicted packing densities were in good agreement with the actual data.

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Dodds, JohnA. "Particle packing characteristics". Powder Technology 61, n. 1 (aprile 1990): 101. http://dx.doi.org/10.1016/0032-5910(90)80071-6.

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Dinger, Dennis R., e James E. Funk. "Particle-Packing Phenomena and Their Application in Materials Processing". MRS Bulletin 22, n. 12 (dicembre 1997): 19–23. http://dx.doi.org/10.1557/s0883769400034692.

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Particle packing is directly controlled by the particle-size distribution of a material being processed. For this reason, particle packing is important to all particulate/fluid systems. After the solids fraction of a body is defined, interparticle chemistry controls how the body will pack and flow. A system of powders can never pack better than the maximum possible level defined by the particle-size distribution alone. Proper control of interparticle chemistry however can help achieve maximum packing, can be used to open the structure, and/or can be used to modify rheological or other process properties.The main goals of particle-packing research have been to determine how systems of particles pack, to develop algorithms for calculating packing densities and porosities for any distribution of particles (spherical or nonspherical, rough or smooth, wet or dry), and to determine how packing and its properties affect the variety of industrial operations that utilize particulate/fluid systems.

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Chen, Yuan, Didier Imbault e Pierre Dorémus. "Numerical Simulation of Cold Compaction of 3D Granular Packings". Materials Science Forum 534-536 (gennaio 2007): 301–4. http://dx.doi.org/10.4028/www.scientific.net/msf.534-536.301.

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During cold compaction processes loose powder is pressed under tooling action in order to produce complex shaped engineering components. Here, the analysis of the plastic deformation of granular packings is of fundamental importance to the development of computer simulation models for industrial forming processes. Powders can be idealized by packing discrete particles, where each particle is a sphere meshed with finite elements. During pressing, particles are deformed by elastic-plastic hardening where friction is present at each contact. The pressing of an isolated particle followed by a body centered cubic packing was compared with numerical prediction and experimental data. The analysis was focused on the interaction between particles and the global response expressed in force-displacement curve during compaction. The accuracy of the numerical models was also analyzed for high relative densities up to 0.95.

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Guo, Ye, Xin Huang e Bao Lin Zhu. "A Calculation Method for Packing Density of Powder in Paste with Continuous Grain Size Distribution". Key Engineering Materials 477 (aprile 2011): 125–31. http://dx.doi.org/10.4028/www.scientific.net/kem.477.125.

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By regarding the powder particles warpped with water film as compounded particles, the packing density of powder particles in actual paste system is transformed into the packing density of compounded partcles in imaginary dry-particle system. Based on Stovall Model, a calculation method for packing density of powder with continuous particle size distribution in paste is developed, and the parameters in the method are dentified by experiment. This calculation method could be used to simulate the packing density of cementitious materials such as cement, fine slag, and fly ashes.

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Roy, D. M., B. E. Scheetz e M. R. Silsbee. "Processing of Optimized Cements and Concretes Via Particle Packing". MRS Bulletin 18, n. 3 (marzo 1993): 45–49. http://dx.doi.org/10.1557/s088376940004389x.

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It has been well-recognized for many years that the particle-size distributions of the cement and the grading of the aggregates play an important role in determining the properties and characteristics of cement and concrete products. DSP (densified with small particles) type cements and concretes, to a certain extent, MDF (macro-defect-free) cements, and optimized concretes are recently recognized outstanding examples of the application of this principle. The preset characteristics of the cementitious slurry are also strongly influenced by these factors. Both the workability of the fresh material, and the microstructure development are controlled to a considerable extent by these geometric parameters.Two seminal works in the areas of continuous particle size distributions and particle packing are those of Andreason and Furnas, respectively. Furnas deals mainly with discrete systems and Andreason with continuous distributions. As early as 1907, the concept of idealized particle packing was being used to optimize cements and concretes. Figure 1a shows an idealized cross section of a simple cubic packing of monodispersed spheres. This system has a maximum packing density of 0.65%. In an ideally packed system of discrete size ranges, the size of the next smallest particles would be such that they just fit in the gaps between the largest size particles, and so on for subsequent particle sizes; this system is represented schematically in Figure 1b. Not only the sizes but also the relative numbers of particles are important; Figures 1c and 1d show systems where some fraction of the smaller and larger particle sizes, respectively, are missing. Figure 1e shows a system where the size of the second largest particles is too large to fit into the gaps between the largest particles, resulting in a lower packing efficiency. Thus, both the particle size and fractions are important when considering packing efficiency.

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Lee, Jong-Heon, W. Jack Lackey e James F. Benzel. "Ternary packing of SiC and diamond particles in ethanol". Journal of Materials Research 11, n. 11 (novembre 1996): 2804–10. http://dx.doi.org/10.1557/jmr.1996.0355.

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Particle packing techniques employing a liquid phase were used for preparation of dense disks of SiC and diamond particulates. Forty-one SiC and fifteen diamond compositions in the ternary-component particle systems were used to determine the optimum percentages of coarse, medium, and fine particles for achieving high packing densities: over 80% for SiC and over 62% for diamond. High packing densities were achieved without vibration by simply mixing the three size fractions in ethanol followed by stirring during the initial evaporation stage. The packing density results for SiC were successfully correlated with the percentages of the coarse and fine particles using multiple regression analysis; however, the data for diamond could not be similarly correlated with particle composition because the experimental work was done in a narrow range of compositions and the range of packing densities was small.

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Tung, K. L., Y. L. Chang, J. Y. Lai, C. H. Chang e C. J. Chuang. "A CFD study of the deep bed filtration mechanism for submicron/nano-particle suspension". Water Science and Technology 50, n. 12 (1 dicembre 2004): 255–64. http://dx.doi.org/10.2166/wst.2004.0721.

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The mechanism of the deep bed filtration for submicron and nano particles suspension was conducted by means of a force analysis on the suspended particles flow path through order-packed granular filter beds. The flow fields through the filter beds were calculated by using the commercial available CFD software - Fluent. Various types of granular packing structures, such as the simple cubic packing, bodycentered packing and face-centered packing structures were chosen for analysis. The motion of suspended particle of 2.967, 0.816, 0.460 and 0.050 μm in diameter, respectively, were tracked by considering the following forces including a net gravitational force, hydraulic drag force, lift force, Brownian force, van der Waals force and a double layer force. The effects of the granular bed packing structure, the porosity of these beds and the suspended particle diameter on the capture efficiency of a granular filter bed were examined. The force analysis depicts that the inertial effect and van der Waals force increased the capture probability of particles on the granular filter bed while the lift force and the Brownian force decreased the particle deposition. Simulated results show that among the chosen packing structures, the face-center packed granular bed gives the greatest pressure drop and capture efficiency of particles due to the lower packing porosity. The simple cubic packed filter bed showed the lowest pressure drop and capture efficiency of particles due to the greatest packing porosity among the chosen packing structures. It is mainly due to the simple cubic packing structure in which there exists the free vertical downward flowing path and thus exhibits a higher packing porosity. The comparisons of the simulated capture efficiency with experimental results depicted that the body-centre packed granular bed showed the best approximation of capture efficiency compared to that of the randomly packed granular bed.

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Wang, Dong, Nima Nejadsadeghi, Yan Li, Shashi Shekhar, Anil Misra e Joshua A. Dijksman. "Rotational diffusion and rotational correlations in frictional amorphous disk packings under shear". Soft Matter 17, n. 34 (2021): 7844–52. http://dx.doi.org/10.1039/d1sm00525a.

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Particles in a packing will rotate when the packing is deformed. We find that rotations display diffusive dynamics set by particle friction and packing fraction. Rotations are spatially anticorrelated and directly indicative of the system pressure.

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Nagy, Endre. "On the three-phase mass transfer with solid particles adhered to the gas-liquid interface". Open Chemistry 1, n. 2 (1 giugno 2003): 160–77. http://dx.doi.org/10.2478/bf02479266.

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AbstractA heterogeneous, multi-layer mass transfer model is proposed for prediction of the effect of multi-layer packing of catalyst particles adhered to the gas-liquid interface. The behavior of the mass transfer rate with respect to the multi-layer packing, to the particle size and mass transfer coefficient without particles is discussed. It is shown that enhancement can be considerably increased by multi-layer packing compared to that of mono-layer packing, depending on the values of particle size and mass transfer coefficient. The predicted mass transfer rates using the proposed model was verified with experimental data taken from the literature. The model presented should be superior to that of published in the literature.

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Huang, Qiu An, Geng Guang Xu e Jian Yu Chen. "Research of the Particle Gradation Technology of Components in PBX Explosive Based on CPM Model". Applied Mechanics and Materials 727-728 (gennaio 2015): 366–69. http://dx.doi.org/10.4028/www.scientific.net/amm.727-728.366.

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Basedon the assumption of related parameters in compressible packing model, thecompressible packing model was used for the calculation of the explosivespacking efficiency. The accuracy of the calculation was verified by experimentsand the relative error was 2.49%. Besides, the influence of content offineparticles and particle size distribution in explosives on stacking efficiencywas discussed. The results show that the stacking efficiency was increasingwith the particle size distribution increasing from 0~300μm to 0~700μm. Thepacking efficiency reached it’s maximum value when we only increased thecontent of fine particles to 40%. Therefore, the packing efficiency has arelation with particle size distribution of raw materials.

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Sudduth, Richard D. "Optimum formulation derivation for the ultimate packing fraction using monodispersed particle sizes when optimizing suspension viscosities". Pigment & Resin Technology 48, n. 1 (7 gennaio 2019): 45–56. http://dx.doi.org/10.1108/prt-01-2018-0006.

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Purpose The importance of maximizing the particle packing fraction in a suspension by maximizing average particle size ratio of D5/D1 has been adequately shown to be important as previously reported in the literature. This study aims to extend that analysis to include the best formulation approach to maximize the packing fraction with a minimum number of monodisperse particle sizes. Design/methodology/approach An existing model previously developed by this author was modified theoretically to optimize the ratio used between consecutive monodisperse particle sizes. This process was found to apply to a broad range of particle configurations and applications. In addition, five different approaches for maximizing average particle size ratio D̅5/D̅1 were addressed for blending several different particle size distributions. Maximizing average particle size ratio D̅5/D̅1 has been found to result in an optimization of the packing fraction. Several new concepts were also introduced in the process of maximizing the packing fraction for these different approaches. Findings The critical part of the analysis to maximize the packing fraction with a minimum number of particles was the theoretical optimization of the ratio used between consecutive monodisperse particle sizes. This analysis was also found to be effectively independent of the maximum starting particle size. This study also clarified the recent incorrect claim in the literature that Furnas in 1931 was the first to generate the maximum theoretical packing fraction possible for n different particles that was actually originally developed in conjunction with the Sudduth generalized viscosity equation. In addition, the Furnas generated equation was also shown to give significantly different results from the Sudduth generated equation. Research limitations/implications Experimental data involving monodisperse particles of different blends with a minimum number of particle sizes that are truly monodisperse are often extremely difficult to obtain. However, the theoretical general concepts can still be applicable. Practical implications The expanded model presented in this article provides practical guidelines for blending pigments using a minimum number of monodisperse particle sizes that can yield much higher ratios of the particle size averages D̅5/D̅1 and thus potentially achieve significantly improved properties such as viscosity. Originality/value The model presented in this article provides the first apparent guidelines to control the blending of pigments in coatings by the optimization of the ratio used between consecutive monodisperse particle sizes. This analysis was also found to be effectively independent of the maximum starting particle size.

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Yang, Zon-Yee, e Shin-Chen Lo. "Describing the geometrical packing of gravelly cobble deposits using pair-correlation functions". Canadian Geotechnical Journal 38, n. 6 (1 dicembre 2001): 1343–53. http://dx.doi.org/10.1139/t01-065.

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There is a close correlation between the mechanical behavior of gravelly cobbles and their geometrical fabric. In geotechnical engineering, the particle-size distribution curve is used to describe the particle gradation. However, a group of particles with the same particle-size distribution can result in several packing arrangements due to the different sedimentation processes. The particle-size distribution curve does not distinguish this characteristic. This study attempts to employ the pair-correlation function of point field theory for describing the geometric packing of gravelly cobble deposits. In the point field, a single gravel- or cobble-sized particle is represented by a point of its geometric center. The pair-correlation function can statistically illustrate the characteristics of a geometrical point pattern and is helpful in interpreting the neighborhood relationship between particles, such as the frequency of interpoint distances and the dominant particle sizes in a point process. Some examples based on ideal particle shapes and arrangements are analyzed to illustrate the interpretations from the pair-correlation functions. The characteristics of pair-correlation functions of field examples are also explained. It is shown that the pair-correlation function can provide another approach to understanding the geometrical packing characteristics of a gravelly cobble formation.Key words: gravelly cobble deposit, geometrical packing, interpoint distance, particle-size distribution, pair-correlation function, point field theory.

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Trulsson, Martin. "Rheology and shear jamming of frictional ellipses". Journal of Fluid Mechanics 849 (26 giugno 2018): 718–40. http://dx.doi.org/10.1017/jfm.2018.420.

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Understanding and predicting dense granular flows is of importance in geology and industrial applications. Still, most theoretical work has been limited to flows and packings composed of discs or spheres, a narrow subset of all possible packings. To advance our understanding of more realistic flows we here study the granular rheology of ellipses in steady-state flow with a focus on the effects of elongation and interparticle friction. We carry out novel numerical simulations of amorphous granular flows in a shear cell under confining pressure, at constant shear rate and at various aspect ratios. Both frictionless and frictional particles are considered. The various rheological curves follow the semi-empirical constitutive relations previously found for granular flows composed of discs or spheres. At the shear jamming point one finds well-defined packings, all characterised by their own set of critical parameters such as critical packing fraction, effective friction, etc. Packings composed of frictionless or almost frictionless particles are found to have a non-monotonic dependence of the macroscopic friction but a monotonic increase in packing fraction as the aspect ratio increases. For packings composed of particles with high interparticle friction the reverse is found. While frictionless packings are found to be hypostatic (except in the disc limit) frictional packings are remarkably close to the isostaticity point of having three contacts per particle. Both frictional and frictionless packings are found to have an increasing nematic ordering as the aspect ratio increases. The onset of a rolling, rather than sliding, motion between very frictional particles diminish this nematic ordering substantially. These findings put new and previously unknown bounds on the packing ratios and yield criteria for these amorphous packings at shear jamming.

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Lam, David C. C. "Packing model for bimodal particle packing with aligned fibers". Journal of Materials Processing Technology 79, n. 1-3 (luglio 1998): 170–76. http://dx.doi.org/10.1016/s0924-0136(98)00007-7.

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Teich, Erin G., Greg van Anders, Daphne Klotsa, Julia Dshemuchadse e Sharon C. Glotzer. "Clusters of polyhedra in spherical confinement". Proceedings of the National Academy of Sciences 113, n. 6 (25 gennaio 2016): E669—E678. http://dx.doi.org/10.1073/pnas.1524875113.

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Dense particle packing in a confining volume remains a rich, largely unexplored problem, despite applications in blood clotting, plasmonics, industrial packaging and transport, colloidal molecule design, and information storage. Here, we report densest found clusters of the Platonic solids in spherical confinement, for up to N=60 constituent polyhedral particles. We examine the interplay between anisotropic particle shape and isotropic 3D confinement. Densest clusters exhibit a wide variety of symmetry point groups and form in up to three layers at higher N. For many N values, icosahedra and dodecahedra form clusters that resemble sphere clusters. These common structures are layers of optimal spherical codes in most cases, a surprising fact given the significant faceting of the icosahedron and dodecahedron. We also investigate cluster density as a function of N for each particle shape. We find that, in contrast to what happens in bulk, polyhedra often pack less densely than spheres. We also find especially dense clusters at so-called magic numbers of constituent particles. Our results showcase the structural diversity and experimental utility of families of solutions to the packing in confinement problem.

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Chen, Z., L. G. Gibilaro e N. Jand. "Particle packing constraints in fluid–particle system simulation". Computers & Chemical Engineering 27, n. 5 (maggio 2003): 681–87. http://dx.doi.org/10.1016/s0098-1354(02)00258-2.

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Cárdenas-Barrantes, Manuel, David Cantor, Jonathan Barés, Mathieu Renouf e Emilien Azéma. "A micro-mechanical compaction model for granular mix of soft and rigid particles". EPJ Web of Conferences 249 (2021): 02008. http://dx.doi.org/10.1051/epjconf/202124902008.

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We use bi-dimensional non-smooth contact dynamics simulations to analyze the isotropic compaction of mixtures composed of rigid and deformable incompressible particles. Deformable particles are modeled using the finite-element method and following a hyper-elastic neo-Hookean constitutive law. The evolution of the packing fraction, bulk modulus and particle connectivity, beyond the jamming point, are characterized as a function of the applied stresses for different proportion of rigid/soft particles and two values of friction coefficient. Based on the granular stress tensor, a micro-mechanical expression for the evolution of the packing fraction and the bulk modulus are proposed. This expression is based on the evolution of the particle connectivity together with the bulk behaviour of a single representative deformable particle. A constitutive compaction equation is then introduced, set by well-defined physical quantities, given a direct prediction of the maximum packing fraction φmax as a function of the proportion of rigid/soft particles.

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He, Li Qun, Ping Wu, Zi Da Li e Li Li Feng. "Dynamics for Dense Packing of Colloids". Advanced Materials Research 465 (febbraio 2012): 248–54. http://dx.doi.org/10.4028/www.scientific.net/amr.465.248.

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Colloidal packing by evaporation is a process that particles are packed by Stokes’ forces. As particles are far from each other, interactions among them are too weak to be taken into account and it’s the Stokes’ force on free particles that is in charge of packing. However, when they are close to some extent, the force is countered by particle interactions. Here, with the aid of force balance model, we demonstrate that the further packing is achieved by all drag forces of particles in the upstream.

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Cao, De Wen, Jia Huan Wang, Yu Qing Sun, Ke Hua Chen, Cheng Ming Yu e Ping Ju Li. "The Effect of the Microstructure of Semisolid Al Alloy on its Rheology". Applied Mechanics and Materials 490-491 (gennaio 2014): 109–12. http://dx.doi.org/10.4028/www.scientific.net/amm.490-491.109.

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In the present work, the effect of the microstructure of AlSi6Mg2 alloy on its macro-rheological behavior of the steady AlSi6Mg2 alloy is investigated. Specifically, the effect of particle size, packing mode and degree of the agglomeration of particles are analyzed. It can be seen that the apparent viscosity decreases with increasing the particle size (d) ifdis between a few μm and 200 μm, while the solid particle size does not affect viscosity except this region. This theoretical prediction is in qualitatively agreement with the experimental data. The trend of the variation of the average agglomerate size with the particle size is the same as the one of viscosity. The packing mode of solid particles in agglomerate is closely related to the solid volume fraction and the characteristics of the alloy system. Subsequently, the state of agglomeration of solid particles which determines the rheology of semisolid AlSi6Mg2 alloy, while the external flow conditions (such as shear rate) influence the viscosity by changing the state of agglomeration. Consequently, the particle size, the packing mode and the average agglomerate size have different effect on the rheological behavior of SSMS.

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Shabaev, Sergey, Sergey Ivanov e Martel Nikita. "The Development of Theoretical Basis of Mathematical Model of Crushed Rock Particle-Particle Packing". E3S Web of Conferences 105 (2019): 01028. http://dx.doi.org/10.1051/e3sconf/201910501028.

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The existing mathematical models that predict the poly-fractional granular media packing density do not take into account their packing degree, which gives a fairly large deviation of the simulation results from the actual experimental values (up to 20-25%). To increase the reliability of prediction of the elastic modulus of crushed rocks, it is necessary to develop the mathematical model that would give more adequate values, since it is known that a change in the granular medium packing density by only 5-10% can lead to a change in the elastic modulus up to 1.5-2 times. The conditions under which smaller particles can be placed in the free space formed after packing larger particles are determined in this work on the basis of the performed computer simulation. It is established that particles of the i-th component of crushed rock can be placed in the free space formed after packing all the previous (larger) components, if the free space volume exceeds the ratio of the actual volume of the particles of the considered component to the packing density of one-dimensional particles to a degree that is exponential function of the serial number of the component.

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Alam, Parvez, e Martti Toivakka. "Fracture and Plasticity in Nano-Porous Particle-Polymer Composites". Key Engineering Materials 462-463 (gennaio 2011): 24–29. http://dx.doi.org/10.4028/www.scientific.net/kem.462-463.24.

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A fracture mechanics algorithm, used for continuum mechanics simulations of nano-porous particle-polymer composites, is described herein. The model comprises close to a thousand ceramic particles bound together by latex polymer. These packings are generated using probabilistic methods (Monte Carlo). Pore-space arises as a function of particle shape and position coupled to the concentration and distribution of latex. Since the bridges are the weakest links in the solid state continuum, an understanding of failure behaviour is paramount for the design and optimisation of these composites. The objective of this research is to statistically characterise adhesive failure at particle-latex interfaces against cohesive failure within the latex bridges. To achieve this, a novel numerical method was developed. This method solves ordinary differential equations for vectors of force and displacement in layers through the computational packing. The model includes a scheme for non-linear elastic behaviour that evolves into a plastic flow regime. The model moreover incorporates a routine for interfacial failure between particulates and binder. Geometrical features such as solid state anfractuosity, bridge orientation, material fraction and coordination numbers are calculated from the packing output. The number of bridges straining plastically within the packing is lower than those that fracture at the interface. Fracture and failure are both related to the particle-binder coordination number. There is no evidence to suggest that decreasing the contacting sizes of binder at interfaces as well as making them thinner will lead to more plastic failure and decrease fracture. Rather, both plastic failure and fracture increase as a function of decreased contacting sizes and bulk diameters. The residual elastic modulus decreases exponentially as the number of broken connections increases.

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Hou, Jinghui, Yifei Ma, Zihan Zhang, Xuanhe Yang, Muhua Huang e Chunpeng Chai. "The Relationship between Solid Content and Particle Size Ratio of Waterborne Polyurethane". Coatings 9, n. 6 (21 giugno 2019): 401. http://dx.doi.org/10.3390/coatings9060401.

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A series of high solid content carboxylic acid/sulfonic acid waterborne polyurethanes was prepared by the emulsion dispersion method. The particle size and solid content were measured. By changing the particle size of the large particles to achieve different particle size ratios, high solid content waterborne polyurethanes were obtained at specific particle size ratios. When the particle size ratio was >7, 4–5 or 2–3, the aqueous polyurethane could reach a higher solid content (more than 56%). This indicated that solid content is related to particle size distribution in high solid content waterborne polyurethane. Moreover, the corresponding three-dimensional stacked models (simple cubic accumulation, face-centered cubic accumulation, cubic close packing and hexagonal closest packing) were established.

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27

Kozlowski, Ryan, Hu Zheng, Karen E. Daniels e Joshua E. S. Socolar. "Particle dynamics in two-dimensional point-loaded granular media composed of circular or pentagonal grains". EPJ Web of Conferences 249 (2021): 06010. http://dx.doi.org/10.1051/epjconf/202124906010.

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Granular packings exhibit significant changes in rheological and structural properties when the rotational symmetry of spherical or circular particles is broken. Here, we report on experiments exploring the differences in dynamics of a grain-scale intruder driven through a packing of either disks or pentagons, where the presence of edges and vertices on grains introduces the possibility of rotational constraints at edge-edge contacts. We observe that the intruder’s stick-slip dynamics are comparable between the disk packing near the frictional jamming fraction and the pentagonal packing at significantly lower packing fractions. We connect this stark contrast in packing fraction with the average speed and rotation fields of grains during slip events, finding that rotation of pentagons is limited and the flow of pentagonal grains is largely confined in front of the intruder, whereas disks rotate more on average and circulate around the intruder to fill the open channel behind it. Our results indicate that grain-scale rotation constraints significantly modify collective motion of grains on mesoscopic scales and correspondingly enhance resistance to penetration of a local intruder.

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HERMANN, A., E. A. LANGARO, S. H. LOPES DA SILVA e N. S. KLEIN. "Particle packing of cement and silica fume in pastes using an analytical model". Revista IBRACON de Estruturas e Materiais 9, n. 1 (febbraio 2016): 48–65. http://dx.doi.org/10.1590/s1983-41952016000100004.

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When added to concrete in appropriate content, silica fume may provide an increase in the mechanical strength of the material due to its high pozzolanic reactivity. In addition to the chemical contribution, physical changes can also be observed in concretes with silica fume due to an improvement in the particle packing of the paste. This is a result of their small size spherical particles, which fill the voids between the larger cement grains. However, it is necessary to properly establish the cement replacement content by silica fume, because at high amounts, which exceed the volume of voids between the cement particles, silica fume can promote the loosening of these particles. Thus, instead of filling the voids and increasing the packing density, the addition of silica fume will increase the volume of voids, decreasing the solid concentration. Consequently, this will impair the properties of the concrete. The objective of this paper is to use a particle packing analytical model, the CPM (Compressible Packing Model), to verify the maximum packing density of cement and silica fume, which could be associated with the silica fume optimum content in pastes. The ideal content of silica fume in pastes, mortars and concretes is usually experimentally determined. However, a theoretical study to contrast experimental data may help understanding the behaviour of silica fume in mixes. Theoretical results show maximum amounts of silica fume in the order of 18 to 20% of the cement weight, which is high considering recommendations on literature of 15%. Nevertheless, the packing model does not consider the effect of silica fume high specific surface on the agglomeration of particles or water demand. Hence, the packing density predicted by this model cannot be used as the single parameter in determining the optimum amount of silica fume in pastes.

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Specht, Eckard. "A precise algorithm to detect voids in polydisperse circle packings". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 471, n. 2182 (ottobre 2015): 20150421. http://dx.doi.org/10.1098/rspa.2015.0421.

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Computer simulations are the primary tool for studying polydisperse particle packings quanti- tatively. For the problem of packing N unequal circles in a larger container circle, nothing is known a priori about the optimal packing (i.e. the packing with the highest packing fraction). Simulations usually start from a random initial configuration with the aim to finish with a dense final packing. Unfortunately, smaller circles often get stuck in trapped positions and prevent the rest of the packing from growing larger. Hence, the knowledge of the structure of unoccupied areas or holes inside a packing is important to be able to move trapped circles into free circular places or voids . A novel algorithm is proposed for detecting such voids in two-dimensional arbitrary circle packings by a decomposition of the contact graph. Combined with a clever object jumping strategy and together with other heuristic methods like swaps and shifts, this approach increases the packing fraction ϕ significantly. Its effectiveness for jumping across the maximally random jammed barrier ( ϕ MRJ ≈0.8575 in the large- N limit) for small benchmark instances as well as for large problem sizes (up to N ≈10 3 ) is demonstrated.

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30

Duriagina, Z. A., I. A. Lemishka, V. V. Kulyk e H. A. Hrydova. "Determination of properties of non-spherical VT20 alloy powders for modelling packing density". Metaloznavstvo ta obrobka metalìv 96, n. 4 (1 dicembre 2020): 56–63. http://dx.doi.org/10.15407/mom2020.04.056.

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The study of unfavorable titanium alloy powders of VT20 grades was carried out and the methods of computer analysis were applied to determine the parameters of their optimal packaging. Metallographic studies were performed on a scanning electron microscope EVO-40XVP, and elemental analysis was performed using an energy dispersion spectrometer OXFORD INCA Energy 350. Determination of particle size distribution of powders was performed using image analysis software ImageJ. The surface morphology of non-spherical particles of VT20 alloy powder was studied for three different fractions: 100 ... 160 μm, 160 ... 200 μm and 200 ... 250 μm. It is shown that the powder particles are characterized by a nonspherical shape and a small difference in size. There is a tendency according to which when the particle size of the powder of the investigated alloy decreases, their shape approaches spherical. According to the results of particle size analysis, it was found that the usual sieve analysis does not allow to fully assess the distribution of powder by fractions. It was found that for the fraction 200 ... 250 μm the dominant particles are with an average diameter of 226 μm, for the fraction 160 ... 200 μm - 177 μm and for the fraction 100 ... 160 μm - 114 μm, respectively. Thus, for the fraction of titanium powder of the BT20 brand 200 ... 250 the polydispersity is 6.4%, for the fraction 160 ... 200 - 8.3%, and for the fraction 100 ... 160 - 9.1%. It is established that the fluidity of titanium alloy powders of the BT20 brand is: for the fraction 200 ... 250 μm - 62.35 s, for the fraction 160 ... 200 μm - 65.44 s, and for the fraction 100 ... 160 - 68, 73 s. That is, the highest value of fluidity is characterized by the powder with the largest particle size. Simulation of the pre-defined volume filling was performed using the "Spheres test" program. The average radii of particles of VT20 titanium alloy powder particles and the probability of the sizes of each of fractions of powder which is necessary at filling of the set volume was calculatedthe possibility of their precipitation have been established. Based on the obtained results, the packing density of VT20 titanium alloy powders was calculated depending on their fractional composition. It is confirmed that as the particle size of the powder decreases, their packing density increases. The surface morphology of non-spherical particles of VT20 alloy powder of different fractional composition and their particle size characteristics were studied. It is shown that with decreasing fractional composition of powder fractions, their homogeneity and bulk density increase. It was found that finer fractions are characterized by poorer fluidity. The simulation results determine the optimal fractional composition of the powder to fill the pre-specified volume. It is shown that as the size of the test particles decreases, their packing density increases. Keywords: additive production, titanium, microstructure, particle size distribution, bulk density, fluidity, packing density modelingmodelling.

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31

Landauer, Johann, Michael Kuhn, Daniel S. Nasato, Petra Foerst e Heiko Briesen. "Particle shape matters – Using 3D printed particles to investigate fundamental particle and packing properties". Powder Technology 361 (febbraio 2020): 711–18. http://dx.doi.org/10.1016/j.powtec.2019.11.051.

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32

Liu, Xiang, e Rui Jie Yu. "Blast Furnace Slag Foundation Packing Grading and Compaction Characteristics Analysis". Applied Mechanics and Materials 368-370 (agosto 2013): 855–59. http://dx.doi.org/10.4028/www.scientific.net/amm.368-370.855.

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Through the packing particles analysis test and heavy compaction test at different depths of new system of Baotou steel finished product of the test section , analysis of the grain size distribution of slag and fly ash mixture and the content of coarse and fine particles on compaction effect are conducted , the results show that the filler embankment foundation is mainly for uniform gradation and continuous filler, when the coarse particle of the filler is 83% ～ 84% content, the compaction effect is best. Using multiple linear regression, the grain size distribution characteristics of the filler particle size equation, coarse and fine particle content and maximum dry density of the regression equation are obtained .

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33

Khirevich, Siarhei, Alexandra Höltzel e Ulrich Tallarek. "Validation of Pore-Scale Simulations of Hydrodynamic Dispersion in Random Sphere Packings". Communications in Computational Physics 13, n. 3 (marzo 2013): 801–22. http://dx.doi.org/10.4208/cicp.361011.260112s.

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AbstractWe employ the lattice Boltzmann method and random walk particle tracking to simulate the time evolution of hydrodynamic dispersion in bulk, random, monodisperse, hard-sphere packings with bed porosities (interparticle void volume fractions) between the random-close and the random-loose packing limit. Using Jodrey-Tory and Monte Carlo-based algorithms and a systematic variation of the packing protocols we generate a portfolio of packings, whose microstructures differ in their degree of heterogeneity (DoH). Because the DoH quantifies the heterogeneity of the void space distribution in a packing, the asymptotic longitudinal dispersion coefficient calculated for the packings increases with the packings’ DoH. We investigate the influence of packing length (up to 150 dp, where dp is the sphere diameter) and grid resolution (up to 90 nodes per dp) on the simulated hydrodynamic dispersion coefficient, and demonstrate that the chosen packing dimensions of 10 dpx 10 dpx 70 dp and the employed grid resolution of 60 nodes per dp are sufficient to observe asymptotic behavior of the dispersion coefficient and to minimize finite size effects. Asymptotic values of the dispersion coefficients calculated for the generated packings are compared with simulated as well as experimental data from the literature and yield good to excellent agreement.

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34

Melnikov, Gennady, Sergey Emelyanov, Nikolay Ignatenko e Olga Manzhos. "The Packing Coefficient of Particles in Structure Cluster Systems". Key Engineering Materials 781 (settembre 2018): 137–42. http://dx.doi.org/10.4028/www.scientific.net/kem.781.137.

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Within the framework of the cluster model, a relation is obtained for calculating the effective diameter of particles and the atomic packing coefficient in the cluster structure, which makes it possible to trace the dependence of the effective particle diameter on the temperature and the quantitative composition of the cluster system. The results of calculating the diameter of particles in a cluster model and classical models of hard and soft spheres are compared. The greatest discrepancy between the predicted particle diameters and the packing coefficients in the cluster structure within the framework of various models is observed near the melting point of the substance, where the difference can reach 16%.

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35

NAKAMURA, Masahiko, e Hironori SUZUKI. "Packing Characteristics of Ultrafine Particle Powder." Journal of the Society of Materials Science, Japan 40, n. 459 (1991): 1566–72. http://dx.doi.org/10.2472/jsms.40.1566.

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36

Xu, Bai-Xiang, Yang Gao e Min-Zhong Wang. "Particle packing and the mean theory". Physics Letters A 377, n. 3-4 (gennaio 2013): 145–47. http://dx.doi.org/10.1016/j.physleta.2012.11.022.

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37

Wright, Jadith K., Mohan J. Edirisinghe, Jian G. Zhang e Julian R. G. Evans. "Particle Packing in Ceramic Injection Molding". Journal of the American Ceramic Society 73, n. 9 (settembre 1990): 2653–58. http://dx.doi.org/10.1111/j.1151-2916.1990.tb06742.x.

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38

Song, Pengcheng, Yufeng Wang, Yu Wang, Andrew D. Hollingsworth, Marcus Weck, David J. Pine e Michael D. Ward. "Patchy Particle Packing under Electric Fields". Journal of the American Chemical Society 137, n. 8 (18 febbraio 2015): 3069–75. http://dx.doi.org/10.1021/ja5127903.

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39

Fruhstorfer, Jens. "Continuous gap-graded particle packing designs". Materials Today Communications 20 (settembre 2019): 100550. http://dx.doi.org/10.1016/j.mtcomm.2019.100550.

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40

Colagrossi, Andrea, B. Bouscasse, M. Antuono e S. Marrone. "Particle packing algorithm for SPH schemes". Computer Physics Communications 183, n. 8 (agosto 2012): 1641–53. http://dx.doi.org/10.1016/j.cpc.2012.02.032.

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41

Coppola, Stephen, e Larry M. Silverberg. "Isotropic packing algorithm for particle simulations". International Journal for Numerical Methods in Engineering 122, n. 17 (19 maggio 2021): 4698–708. http://dx.doi.org/10.1002/nme.6742.

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42

Thiede, Tobias, Tatiana Mishurova, Sergei Evsevleev, Itziar Serrano-Munoz, Christian Gollwitzer e Giovanni Bruno. "3D Shape Analysis of Powder for Laser Beam Melting by Synchrotron X-ray CT". Quantum Beam Science 3, n. 1 (19 febbraio 2019): 3. http://dx.doi.org/10.3390/qubs3010003.

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Abstract (sommario):

The quality of components made by laser beam melting (LBM) additive manufacturing is naturally influenced by the quality of the powder bed. A packing density <1 and porosity inside the powder particles lead to intrinsic voids in the powder bed. Since the packing density is determined by the particle size and shape distribution, the determination of these properties is of significant interest to assess the printing process. In this work, the size and shape distribution, the amount of the particle’s intrinsic porosity, as well as the packing density of micrometric powder used for LBM, have been investigated by means of synchrotron X-ray computed tomography (CT). Two different powder batches were investigated: Ti–6Al–4V produced by plasma atomization and stainless steel 316L produced by gas atomization. Plasma atomization particles were observed to be more spherical in terms of the mean anisotropy compared to particles produced by gas atomization. The two kinds of particles were comparable in size according to the equivalent diameter. The packing density was lower (i.e., the powder bed contained more voids in between particles) for the Ti–6Al–4V particles. The comparison of the tomographic results with laser diffraction, as another particle size measurement technique, proved to be in agreement.

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43

Luo, Lisha, Zhifu Shen, Xudong Wang e Hongmei Gao. "Evolution of rattling particles in deviatoric shear deformation of granular material". EPJ Web of Conferences 249 (2021): 11017. http://dx.doi.org/10.1051/epjconf/202124911017.

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Granular material such as clean sand in geotechnical engineering is characterized by structured internal deformation pattern and some interesting particle arrangement patterns. This study focuses on the evolution of the fraction of rattling particles in deviator deformation until the critical state. Numerical simulations using the discrete element method reveal the presence of rattling particles (with zero or only one contact with neighbouring particles) even in a very dense packing system. The results show that the initial fraction of rattling particles depends on sample density and particle size distribution. With the increase of deviator strain, the number and volume fractions of rattling particles gradually approach a steady critical state from either a loose or a dense starting point. An effective void ratio, which is calculated by treating rattling particles as voids, can be viewed as new state parameter describing the effective packing density of sands. Besides, the rattling behaviour strongly depends on particle size distribution.

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44

Assarsson, A., I. Nasir, M. Lundqvist e C. Cabaleiro-Lago. "Kinetic and thermodynamic study of the interactions between human carbonic anhydrase variants and polystyrene nanoparticles of different size". RSC Advances 6, n. 42 (2016): 35868–74. http://dx.doi.org/10.1039/c6ra06175c.

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45

Xu, Zhiwei, Michael Yu Wang e Tianning Chen. "An Experimental Study of Particle Damping for Beams and Plates". Journal of Vibration and Acoustics 126, n. 1 (1 gennaio 2004): 141–48. http://dx.doi.org/10.1115/1.1640354.

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This paper describes an experimental investigation of a particle damping method for a beam and a plate. Tungsten carbide particles are embedded within longitudinal (and latitudinal) holes drilled in the structure, as a simple and passive means for vibration suppression. Unlike in traditional damping materials, mechanisms of energy dissipation of particle damping are highly nonlinear and primarily related to friction and impact phenomena. Experiments are conducted with a number of arrangements of the packed particles including different particle sizes and volumetric packing ratios. The results show that the particle damping is remarkably effective and that strong attenuations are achieved within a broad frequency range. The effects of the system parameters including particle size, packing ratio and particle material are studied by broadband and narrowband random excitations. The experimental results confirm a numerical prediction that shear friction in the longitudinal (and the latitudinal) directions is effective as the major contributing mechanism of damping in the case. Another unique feature of linear decay in free vibrations is also observed in this case of particle damping.

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46

Qi, Yang, e Jin Min Wang. "The Particle Swarm Optimization Algorithm for Solving Rectangular Packing Problem". Advanced Materials Research 186 (gennaio 2011): 479–83. http://dx.doi.org/10.4028/www.scientific.net/amr.186.479.

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Based on extensive researches on various heuristic algorithms, the particle swarm optimization algorithm was developed to solve the rectangular packing problems. The algorithm optimizes the parameter of dynamic attractive factors by updating the position and the velocity of the particles, and applies perturbation strategy to solve the matter that it is easy to stick at local optima. The experimental result shows that the algorithm can get a better packing result by less time.

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47

Cersonsky, Rose K., Greg van Anders, Paul M. Dodd e Sharon C. Glotzer. "Relevance of packing to colloidal self-assembly". Proceedings of the National Academy of Sciences 115, n. 7 (30 gennaio 2018): 1439–44. http://dx.doi.org/10.1073/pnas.1720139115.

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Since the 1920s, packing arguments have been used to rationalize crystal structures in systems ranging from atomic mixtures to colloidal crystals. Packing arguments have recently been applied to complex nanoparticle structures, where they often, but not always, work. We examine when, if ever, packing is a causal mechanism in hard particle approximations of colloidal crystals. We investigate three crystal structures composed of their ideal packing shapes. We show that, contrary to expectations, the ordering mechanism cannot be packing, even when the thermodynamically self-assembled structure is the same as that of the densest packing. We also show that the best particle shapes for hard particle colloidal crystals at any finite pressure are imperfect versions of the ideal packing shape.

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48

Cheng, Yun-Hong, Bao-Long Zhu, Si-Hui Yang e Bai-Qiang Tong. "Design of Concrete Mix Proportion Based on Particle Packing Voidage and Test Research on Compressive Strength and Elastic Modulus of Concrete". Materials 14, n. 3 (29 gennaio 2021): 623. http://dx.doi.org/10.3390/ma14030623.

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According to the basic principle of dense packing of particles, and considering the interaction between particles, a dense packing model of granular materials in concrete was proposed. During the establishment of this model, binary particle packing tests of crushed stone and sand were carried out. The fitting analysis of the test results determines the relationship between the particle size ratio and the remaining volume fraction of the particle packing, and then the actual void fraction of the particle packing was obtained, based on which the water–binder ratio was combined to determine the amount of various materials in the concrete. The proposed concrete mix design method was used to prepare concrete, and its compressive strength and elastic modulus were tested experimentally. The test results show that the aggregate volume fraction of the prepared concrete increased, and the workability of the concrete mixture with the appropriate amount of water reducing agent meets the design requirements. When the water–binder ratio was 0.42, 0.47, or 0.52, the compressive strength of the concrete increased compared with the control concrete, and the degree of improvement in compressive strength increased with the decrease in water–binder ratio; when the water-binder ratio was 0.42, 0.47, or 0.52, the static elastic modulus of the concrete increased compared with the control concrete, and the degree of improvement in elastic modulus also increased with the decrease in water–binder ratio. The elastic modulus and compressive strength of the prepared concrete have a positive correlation. Findings show that the concrete mix design method proposed by this research is feasible and advanced in a sense.

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Zhao, Kun, Shu Min Wan e Bin Lin. "Visualization of Random Particle Packing Model for Resin Concrete". Applied Mechanics and Materials 217-219 (novembre 2012): 1483–86. http://dx.doi.org/10.4028/www.scientific.net/amm.217-219.1483.

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Particle packing model are always utilized to investigate and predict micro structure performance of material. On one hand, considering 3 classical packing methods, it’s found that random packing method for model of resin concrete is the most suitable. 3D Particle packing model on Matlab is realized through compiling programs, then converted into Ansys and study on porosity of it proves the correctness of the packing model. On the other hand, different from others’ applying Walraven J.C Equation with a quite limited applicability to getting slice, this paper proposes that slice directly from the 3D model is more accurate and scientific, which is also managed to realize on both Matlab and Ansys.

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Mader-Arndt, Katja, Zinaida Kutelova, Regina Fuchs, Jan Meyer, Thorsten Staedler, Werner Hintz e Jürgen Tomas. "Single particle contact versus particle packing behavior: model based analysis of chemically modified glass particles". Granular Matter 16, n. 3 (19 gennaio 2014): 359–75. http://dx.doi.org/10.1007/s10035-013-0478-9.

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