Role Of Volume Fraction Research Articles

Significance of Lorentz and Coriolis forces on dynamics of water based silver tiny particles via finite element simulation

This study is briefings the roles of volume fraction, Coriolis, and Lorentz forces on the dynamics of rotating water based silver tiny particles flow toward a continuously stretching sheet. The Coriolis force play a significance role on the dynamic of fluid in oceanography, Astrophysics, meteorology, and Stellar dynamics by effecting the fluid movement on the earth surface. The nanoparticles are incorporated because of their unusual qualities like upgrade the thermal transportation, which are very important in heat exchangers, modern nanotechnology, electronics, and material sciences. The primary goal of this study is to improve heat transportation. Appropriate similarity transformations are applied for the principal PDEs to transform into nonlinear dimensionless PDEs. A widely recognized Numerical scheme known as the Finite Element Method is employed to solve the resultant convective boundary layer balances. It is seen that growing contributions of the Coriolis, and Lorentz forces cause to decline the primary and secondary velocities, but the temperature function and skin friction factor show opposite trend. The temperature distribution and reduced Nusselt number are prominent against growing volume fraction, but inverse trend is observed for velocities distributions. These examinations are relevant to the field of plastic films, crystal growing, paper production, heat exchanger, and bio-medicine.

The Role of Volume Fraction and Additives on the Rheology of Suspensions of Micron Sized Iron Particles

The increase of the yield stress versus the magnetic field is the most important quantity characterizing the efficiency of a magnetorheological suspension. The theory based on the formation of columnar aggregates predicts a linear variation with the volume fraction of magnetic particles. We shall review previous models for the calculation of forces and yield stress and will introduce a new one based on rupture at zero strain. The predictions of these models are compared with the experimental data obtained for carbonyl iron particles by different authors. Whereas previous analytical prediction strongly overestimates experimental yield stress, the one calculated from Finite Element Method (FEM) used with affine trajectories well reproduce the experiments and show a linear dependence with the volume fraction and a H3/2 behavior between 50 and 200kA/m. Nevertheless, at very high volume fractions (>55%) where the suspension can only flow in the presence of specific additives, the dependence of the yield stress versus the volume fraction and the magnetic field is dramatically changed. We observe a jamming transition which is triggered by the application of a low magnetic field and which depends strongly of the volume fraction. We will discuss the new perspectives arising by the use of these very high volume fractions.

Dynamic electrophoretic mobility and electric permittivity of concentrated suspensions of plate-like gibbsite particles

In this paper we present experimental results on the electrokinetic behavior of planar gibbsite particles in concentrated suspensions. The dc electrophoretic mobility measurements are in this case of little significance, as they are scarcely informative. In the present investigation, we show that the dielectric dispersion and dynamic electrophoresis can in contrast provide such information. The complicating factors are of course the non-spherical shape and the finite particle concentration, as no complete theory of these phenomena exists for such systems. We propose to use first of all a model of dynamic electrophoresis of spheroids in which the effect of volume fraction is considered by means of an approximate theory previously obtained for spheres, based on the evaluation of electrical and hydrodynamic interactions between particles. In addition, the role of volume fraction on the high frequency inertial relaxation is also ascertained and used to obtain a volume fraction-independent radius of the gibbsite spheroids. A similar approach is used for the evaluation of dielectric dispersion data. Both the dynamic mobility and dielectric constant dependencies on frequency were obtained for gibbsite suspensions of different volume fractions in 0.5mMKCl. The theoretical treatments elaborated were applied to these data, and a coherent picture of the geometrical and electrical characteristics of the particles was obtained.

The direct and indirect effects of nanotwin volume fraction on the strength and ductility of coarse-grained metals

Coarse-grained (CG) metals strengthened by nanotwinned (NT) regions have an excellent combination of high strength and good ductility. In this paper, numerical simulations based on the mechanism-based strain gradient plasticity and the Johnson–Cook failure criterion are carried out to investigate the direct and indirect effects of volume fraction of the NT regions and several other key attributes on the strength and ductility of the CG metal strengthened by NT regions. Our results indicate that twin spacing, shape, distribution, and volume fraction of NT regions all have significant effects, and that, as the volume fraction increases, the roles played by the twin spacing and shape of NT regions also change. At low volume fraction of NT regions, their shape is found to have a significant influence on the overall ductility. As the volume fraction increases, the shape effect on the ductility is found to diminish even though the effect on the strength is noted to continue to enhance. While twin spacing and volume fraction of NT regions have shown different effects on the ductility, the effect of twin spacing always decreases as the volume fraction increases. During the simulations we have also discovered several intrinsic deformation and failure mechanisms through the analysis of microcrack initiation sites and microcrack propagation paths. It is believed that this simulation has revealed significant insights into the roles of volume fraction, twin spacing, shape, and distribution of NT regions on the strength and ductility of this novel class of materials.

Dynamics of drop formation in granular suspensions: the role of volume fraction

The presence of grains strongly modifies the detachment of drops of a viscous liquid. We have shown previously that the detachment of drops of granular suspensions takes place via different regimes (Bonnoit et al. submitted, 2011). Here we study the influence of the volume fraction of particles on the formation and shape of the droplets by means of visual observations. We measure the minimal neck diameter as well as the height of the detachment as a function of time to quantify the evolution of the drop shape. We also address the question of the thinning dynamics of the neck in the different regimes. Linking the dynamics to the properties of the effective fluid or to rearrangements of individual grains in the thread gives insights in the origin of the different regimes.

Synthesis and Characterization of Al–SiC Nanocomposites Produced by Mechanical Milling and Sintering

Aluminum powder and various volume fractions of SiC particles with an average diameter of 50 nm were milled by a high-energy planetary ball mill to produce nanocrystalline Al–SiC nanocomposite powders. Double pressing/sintering process was used to consolidate powders to cylindrical specimens. It was shown that a double cycle of cold pressing and sintering can be utilized to obtain high density Al–SiC nanocomposite parts without using a hot-working step. High resolution scanning electron microscopy (HRSEM), X-ray diffraction (XRD) and laser particle size analyzer (PSA) were used to study the morphological and microstructural evolution of nanocomposite powders and bulk samples. The role of volume fraction of SiC nanoparticles in grain size of both as-milled and as-consolidated aluminum matrix was investigated. It was found that the presence of the higher SiC particles eventuate to slowly decrease in grain size of aluminum matrix powders. However, this trend is strongly noticeable in grain size of consolidated samples. The pinning effects on grain stability by SiC nanoparticles were quantitatively analyzed. It was found that Gladman's model is in close agreement with the experimentally determined grain size of Al–SiC nanocomposites.

Behavior of high performance fiber reinforced cement composites under multi-axial compressive loading

Experiments were conducted to better understand the behavior of strain hardening, high performance fiber reinforced cement composites (HPFRCC) when subjected to uniaxial, biaxial, and triaxial compression. The experimental parameters were: type of fiber, fiber volume fraction, and loading path. Two types of commercially available fibers, namely high-strength hooked steel fiber and ultra high molecular weight polyethylene fiber, with volume fractions ranging from 1.0% to 2.0%, were used in a 55-MPa mortar matrix. The selected loading paths consisted of uniaxial compression and tension, equal biaxial compression, and triaxial compression with two levels of lateral compression. The test results revealed that the inclusion of short fibers can significantly increase both strength and ductility under uniaxial and biaxial loading paths, but that the role of volume fraction is rather small for the range of fiber volume contents considered. The results also showed that the confining effect introduced by the fibers becomes minor in triaxial compression tests, where there is relatively high external confining pressure. The experimental information documented herein can serve as input for the development of multiaxial constitutive models for HPFRCCs.

Crystal Topology Prediction in Alternating Amphiphiles: Aromatic Polyethers and the Role of Volume Fraction

The crystal structures of alternating aromatic polyethers in the Cambridge Structural Database have been analyzed. Alternating aromatic polyethers are chain or ring-like molecules in which there is a regular alternation between the aromatic and the polyether moieties. In all structures examined, a clear interface is present between the hydrophobic aromatic and the hydrophilic polyether moieties. An examination of the 21 structures where the ratio of the hydrophobic-to-total volume ratio is 40−50% shows that 14 of the structures are lamellar (i.e., have alternating hydrophobic and hydrophilic layers within the structure). These results suggest that other as yet unsynthesized aromatic polyethers will also adopt lamellar crystal topologies. We prepared two such systems 1,5-bis(1,3-dioxolan-2-ylmethoxy)-naphthalene, 1 and 1,5-bis(2-methoxyethoxy)-naphthalene, 2 (Scheme 1). Solution of their single-crystal structures revealed that both crystallize in a lamellar topology. The connection between our findings and...

Structure Rationalization and Topology Prediction of Two-Distinct-Component Organic Crystals: The Role of Volume Fraction and Interface Topology

We consider here small-length-scale crystal structures with two clearly different molecular components (e.g., hydrophobic and hydrophilic). Using a perspective developed by studies on large-length-scale block copolymers and liquid crystals, we focus on the crystalline interface between the two components. We examine four types of two-component crystals: aromatic ammonium carboxylates, aromatic oligo(ethylene oxides), cyclohexylammonium carboxylates, and ether-thioether compounds. Of the 111 crystal structures found in the Cambridge Structure Database (CSD), 108 adopt one of the five generic topologies found in diblock copolymers: spheres, columns, perforated layers, layers, and bicontinuous structures. As in diblock copolymers, a key factor controlling the interfacial topology is shown to be the volume ratio of the two components. When the volume fraction of one component is less than 30% of the whole, more than five-sixths of the examined crystal structures are of columnar or spherical type. For volume fractions between 40 and 50% more than three-quarters are of lamellar or bicontinuous type. We use this model to predict the topologies of small-length-scale two-component crystals. We predict the crystal topolgies of six new crystal structures: three are predicted to be columnar, and the other three, lamellar or bicontinuous. The crystal structures of these systems were then determined by single-crystal X-ray methods. Five of the structures form in topologies consistent with the predictions: three in columns and two in layers. The remaining one forms as a perforated layer instead of the predicted columnar structure. Such predictive accuracy is consistent with the statistics of the CSD investigation.

Role of volume fraction in the coarsening of Ni 3Si precipitates in binary NiSi alloys

The coarsening behavior of coherent γ′ (Ni 3Si) precipitates in binary NiSi alloys containing 5.50–5.93 wt.%Si was investigated at an aging temperature of 650°C. Over this range of concentrations the volume fractions ƒ γ′ vary from approximately 0.015 to 0.081. The kinetics of coarsening and the distributions of particle sizes appear to be independent of volume fraction for ƒ γ′ = 0.050, 0.058 and 0.081 , but semiquantitative evidence was found for anomalously rapid coarsening kinetics when ƒ γ′ = 0.018 . The larger precipitates in the more dilute alloys exhibit concave-cuboidal morphologies and in some instances were observed in the process of splitting into groups of eight new particles. These morphologies were also attained under even smaller supersaturations than those experienced during normal isothermal aging, i.e. in a microstructure produced by a double-aging experiment. This suggests to us that the morphologies in question are not a product of dendritic growth. These rather unexpected results indicate that the role of elastic energy in affecting morphology and coarsening kinetics may be more important than previously suspected, since the Ni 3Si-matrix lattice misfit is smaller than in any other binary Ni-base alloy. There is also evidence, based on our results and data in the literature, that the coarsening kinetics might increase with increasing ƒ γ′ at volume fractions exceeding 0.10; this is more in keeping with the kind of behavior expected theoretically.

Steady state creep behaviour of silicon carbide particulate reinforced aluminium composites

The roles of volume fraction and size of reinfrecement on the steady state creep behaviour of pure aluminium matrix-silicon carbide particulate composites have been studied in the temperature range 623–723 K. The observed apparent stress exponents are higher than 15 and apparent activation energy is 249 kJ mol −1. By considering the existence of a threshold stress, the data for 1.7 μm particulate reinforced composites with different volume fraction can be rationalized according to the substructure invariant model. The effective stress-strain rate behaviour of composites with 10 vol.% of coarser particulates (14.5 and 45.9 μm), however, agree with the stress dependent substructure model. The present analysis is validated by constructing a new type of “dislocation creep mechanism map”. The observed threshold stress varies with the volume fraction of reinforcement and is independent of particulate sizes and test temperatures. It is suggested that a model based on applied stress independent load transfer is required to explain the origin of such a threshold stress.

Pressure/volume/surface area relationships in foams and highly concentrated emulsions: role of volume fraction

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPressure/volume/surface area relationships in foams and highly concentrated emulsions: role of volume fractionH. M. PrincenCite this: Langmuir 1988, 4, 1, 164–169Publication Date (Print):January 1, 1988Publication History Published online1 May 2002Published inissue 1 January 1988https://doi.org/10.1021/la00079a030RIGHTS & PERMISSIONSArticle Views373Altmetric-Citations28LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (658 KB) Get e-Alerts Get e-Alerts