Effect Of Particle Size Ratio Research Articles

Shear modulus and damping ratio of granulated rubber-sand mixtures: Influence of relative particle size

Rubber-sand mixtures (RSM) have gained recognition as a valuable, lightweight, and cost-efficient energy-absorbing material with extensive potential application in engineering construction. However, the small-strain dynamic properties and prevailing mechanisms of RSM have not been thoroughly understood. This study conducted a series of resonant column tests on the small-strain dynamic modulus and damping ratio of RSM, considering the effects of particle size ratio (PSR), rubber content (RC), and confining pressure. The results reveal that the dynamic shear modulus of RSM generally decreases with increasing RC and increases with rising confining pressure. For all RC and confining pressure levels, the maximum dynamic shear modulus of RSM reaches the minimum value as the PSR approaches 1.0. In this case, the dynamic shear modulus of RSM decreases most gently with the strain. The addition of rubber consistently augments the damping ratio, whereas the PSR initially diminishes the damping ratio before eventually enhancing it. Simultaneously, as the PSR is nearing 1.0, the damping ratio achieves its lowest point. Furthermore, new empirical equations were developed to quantitatively analyze the dynamic properties of RSM, in which the predicted values of the dynamic shear modulus and the modulus attenuation coefficient show good agreement with the observed values. This work will facilitate the preparation of artificial RSM-cored geotechnical seismic isolation layers tailored to specific engineering requirements.

Settling dynamics and thresholds for breakup and separation of bi-disperse particle clouds

Settling dynamics and thresholds for breakup and separation of bi-disperse particle clouds

Determination of the size of representative volume element for gap-graded granular materials

Gap-graded granular soils have a wider grain size distribution and more heterogeneous fabric structure than normal soils. It is critical to choose the sample size of element tests in a faithful and repeatable manner. The Discrete Element Method (DEM) is utilized to determine the size of representative volume element (RVE) of gap-graded mixtures with varying particle size distributions. Over seven hundred triaxial tests are performed to investigate the effect of particle size ratio and coarse fraction on the typical RVE size. Microscopic parameters are analyzed to validate the reproducibility of the determined RVE sizes. The optimal RVE size is negatively proportional to particle size ratio and positively correlated with the coarse fraction. Empirical equations are further established to correlate the RVE sizes with particle size ratios for different coarse fractions. The findings may provide a useful reference for experimental and numerical studies in choosing the RVE size for gap-graded soils.

Effect of Particle Size Ratio on Microstructure and Active Material Utilization in Argyrodyte All-Solid-State Composite Cathodes

Among next-generation batteries, all-solid-state batteries (ASSB) promise increased energy densities, fast charging properties, and higher safety compared to traditional liquid-based systems. To achieve the demanded high energy densities high mass loadings of the composite cathodes are necessary. These consist of active material (AM), solid electrolyte (SE), and conductive additive as well as binder. Volume changes of intercalation AM and insufficient ionic percolation at low SE contents lead to an increased interfacial resistance and capacity loss. In order to promote cathode AM utilization the particle size ratio of the AM and the SE within the composite cathode needs to be optimized.Theoretical calculations have shown that for high AM utilization at high AM loadings particle size ratio is a crucial parameter [1, 2]. Experimentally, the influence of particle size ratio has so far only been studied at laboratory scale. However, scalable process routes have not considered this important aspect. In this work, we present a solvent-based process route for the preparation of sulfide-based solid-state composite cathodes with NCM622 as AM, starting from the adjustment of the particle size of a commercially available Li6PS5Cl SE by planetary ball mill. Further process steps include the dispersion of SE with AM and conductive additive and doctor blade coating of cathode films. We analyzed the composite cathodes with regard to their internal resistance as well as their microstructure and conducted electrochemical tests in lab-scale test cells. Optimization of the particle size ratio results in an increase of AM utilization by a factor of 5 as well as an enhanced AM-SE-particle contact area and lower porosity.

Effect of particle size ratio and fines content on drained/undrained behavior of binary granular soil according to confining pressure and packing density: a DEM simulation

Effect of particle size ratio and fines content on drained/undrained behavior of binary granular soil according to confining pressure and packing density: a DEM simulation

Size segregation of disk particle in two-dimensional chute.

Size segregation will lead to stratification of a particle system. At present, people have not fully understood the segregation mechanism. In this work, we have studied the size segregation behavior of two-component disk particles in chute flows. The effects of particle size ratio η, particle density ρ, static friction coefficient μ and chute angle α on size segregation are discussed. We use the discrete element method to simulate and calculate the force of disk large particles during segregation. Results show that the 'squeeze expulsion' mechanism plays a key role in the size segregation of a disk particle flow. We establish a physical model of 'squeeze expulsion' of disk particles and obtain the conditions for the formation of 'squeeze expulsion' mechanism.

Research on the Inertial Migration Characteristics of Bi-Disperse Particles in Channel Flow

The inertial focusing effect of particles in microchannels shows application potential in engineering practice. In order to study the mechanism of inertial migration of particles with different scales, the motion and distribution of two particles in Poiseuille flow are studied by the lattice Boltzmann method. The effects of particle size ratio, Reynolds number, and blocking rate on particle inertial migration are analyzed. The results show that, at a high blocking rate, after the same scale particles are released at the same height of the channel, the spacing between the two particles increases monotonically, and the change in the initial spacing has little effect on the final spacing of inertial migration. For two different size particles, when the smaller particle is downstream, the particle spacing will always increase and cannot remain stable. When the larger particle is downstream, the particle spacing increases firstly and then decreases, and finally tends to be stable.

Preparation, mechanical, and leaching properties of CaZrO3 ceramic cores

AbstractThe CaZrO3 ceramic core materials with excellent mechanical and chemical properties were successfully prepared using single‐phase CaZrO3 powders. Effects of particle size ratio and sintering temperature on the mechanical and chemical properties of CaZrO3 ceramic core materials were researched. The chemical property was analyzed by leaching research of core materials in 10 wt% and 20 wt% HNO3 solution at the boiling point. Results showed that the suitable particle size ratio was important for the preparation of CaZrO3 ceramic core materials with excellent comprehensive properties. The addition of fine particles in ceramic core materials promoted the densification process owing to the framework formed by coarser particles and sintering neck formed by fine particles between coarse particles, which was beneficial for further improving their bending strength. When the content of particles with 200 mesh size was 80wt%, the highest bending strength was obtained, 54.38 ± 5.28 MPa. The porosity was 17.45% and the volume density was 3.86 g/cm3. The increasing sintering temperature increased the densification of CaZrO3 ceramic core materials by offering the sintering driving force, further leading to the improvement of bending strength. When the temperature was 1650℃, at the 20% content of particles with 200 mesh size, the highest bending strength of CaZrO3 cores reached 51.01 ± 5.18 MPa. Meanwhile, the porosity was 18.65% and the volume density was 3.83 g/cm3. Additionally, the CaZrO3 samples could be effectively leached in 10 wt% HNO3 solution. Therefore, CaZrO3 materials with good mechanical and leaching properties were believed to be a suitable candidate for ceramic core materials in the investment casting of alloys with high melting point.

A modified calculation of particle buoyant forces in vibro-fluidized beds

Segregation of granular materials under vibration or flow conditions such as the Brazil nut effect has been well known, however, there is yet no consensus mechanisms to explain this phenomenon. This study attempts to investigate particle buoyant forces in the segregation process. To explain the difference of the segregation behavior for the large particle with different size, a modified calculation method of particle buoyant force is suggested for considering the effect of particle size ratio. A simple verification illustrates its validity.

Research on quantitative method of particle segregation based on axial center nearest neighbor index

The phenomenon of particle segregation generally occurs during the operation of the ball mill. However, the traditional quantitative index of particle mixing and segregation degree is suitable for overall segregation, which cannot accurately reflect the axial segregation. For the problem of axial segregation of particulate matter in the rotating drum, an axial center nearest neighbor index (ACNN) method is proposed. The method uses the nearest neighbor segregation factor and the center compensation distance to measure the mixing and segregation, and further characterizes the evolution of the particle–particle positional relationship in the particle system, reflecting the degree of spatial and temporal mixing and segregation. The comparison of the experimental and simulation results shows that the ACNN method can accurately quantify the overall segregation degree based on the instantaneous information about the particles in the different shaft sections. By comparing and analyzing the relationship between different shaft segments and the overall segregation degree, the particle mixing and segregation process of the different shaft segments in the rotating drum was studied. The results show that an indicator of the overall degree of segregation cannot be acquired by observing a single shaft section. The effects of particle size ratio and density ratio compete with each other, but promote different segregation pattern of particles respectively. The axial segregation of the drum is characterized by smaller particles gathering towards the middle of the drum, and a large length to diameter ratio (L/D) has a restraining effect on segregation characteristics.

Studying the particle size ratio effect on granular mixing in a vertically vibrated bed of two particle types

The uniform mixing of solids is important in many industries, such as the pharmaceutical, food, petrochemical and chemical industries. We numerically investigated the effect of particle size ratio on the mixing of bisized particles in a quasi-two-dimensional vibrationally fluidized bed. The granular binary mixtures comprised spherical particles with different size ratios. Three-dimensional discrete-element simulations agreed with previous experimental results. Convective and diffusive mechanisms occurred within the vibrated bed. The particle size had no significant influence on convective mixing, whereas the diffusive mechanism strengthened for large size ratios. The average particle velocity was larger in a mixture of large size ratios. The stronger diffusive motion and larger average particle velocity caused the particles to mix faster for large size ratios. The final mixing index decreased with size ratio because of the difference between the size and number of small and large particles.

Structural and Micromechanical Properties of Ternary Granular Packings: Effect of Particle Size Ratio and Number Fraction of Particle Size Classes.

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.

Structural signature of binary sphere mixtures under air impact

Packings of binary spheres formed under air impact were simulated using the coupled computational fluid dynamics (CFD) and discrete element method (DEM) approach. The effects of particle size ratio (PSR) on structural properties of the packings before and after air impact were analysed. The results showed that the air impact condensed the packings. The second peak in the RDF curves became more apparent and the third peak gradually disappeared in the final packings with increasing PSR. The number of contacts between large spheres decreased, while the contacts between large and small spheres increased under the effect of air impact. The orientation of the contacts tended to be more directional for the final packings. Radical tessellation analyses indicated that for both initial and final packings, two peaks were always formed in the distributions of face number per cell, face area and relative volume, while only one peak appeared in the distributions of edge number and perimeter. Furthermore, the average metrical properties for large particles hardly changed with PSR in the final packings, while those for small or all particles decreased after air impact.

Effect of aluminum to alumina particles size ratio on the microstructural aspects of aluminide coatings by LTHA pack cementation

In this study, the effects of particle size ratio of filler particles (alumina) and metal source (aluminum) on the microstructural aspects of low-temperature high-activity (LTHA) aluminized coatings were investigated. For this purpose respectively, Ala, Alb, and Alc powders with a mean particle size of 250, 20 and 3 μm and alumina powder with a mean particle size of 44 μm were used. According to SEM-EDS analysis, the average thickness of the coatings created by Ala, Alb and Alc powders in the pack aluminizing process was measured to be 92.4, 89.6, 56.4 μm, respectively. It was found that the thickness of aluminide coatings after the first step of LTHA process is directly influenced by the aluminum and nickel concentration gradient between the top and bottom of the coatings. The linear atomic distribution of Al, Ni, Cr, and Ti elements was compared throughout the coatings. According to the results, the coating produced by Alb had the highest Al concentration in its composition which shows the higher rate of AlCln production and deposition on the surface of the coating. The optimized aluminum to the alumina ratio can lead to enhancing gas-state diffusion due to inhibiting the local melting and sintering of Al particles.

Effect of particle size ratio on shear-induced onset of particle motion at low particle Reynolds numbers: From high shielding to roughness

We study incipient motion of single beads on regular substrates made of spherical particles of a different size in steady shear flow at small particle Reynolds numbers. We cover a large range of sizes: from small beads that are highly shielded from the shear flow by the substrate spheres, and hence, are susceptible to the flow through the interstices of the substrate, to beads fully exposed to the flow, where the substrate rather acts like roughness of an otherwise flat surface. Numerical and experimental studies agree within measurement uncertainty. To describe the findings, we extend a recently derived model for particles of equal size which was validated over a wide range of substrates [Agudo et al., “Shear-induced incipient motion of a single sphere on uniform substrates at low particle Reynolds numbers,” J. Fluid Mech. 825, 284–314 (2017)]. The extended model covers the entire spectrum of size ratios, where the critical Shields number varies from about zero to infinity. The model properly describes the numerical and experimental data. For well exposed beads, we find a scaling law between the critical Shields number and the size ratio between mobile bead and substrate spheres with an exponent of −1.

Particle size ratio and distribution effects on packing behaviour of crushed GMZ bentonite pellets

High-density bentonite pellets have been considered as an alternative sealing or buffer material for nuclear waste repository. Investigation on the packing behaviour of pellets is of great interest due to the significant impacts of global density on the hydro-mechanical behaviors of the material. In this manuscript, the packing behaviour of mono-size, binary-size, ternary-size and multi-size mixtures of crushed bentonite pellets were experimentally investigated. The effects of particle size ratio and distribution on packing dry density were analyzed. Results indicate that, for mono-size mixtures, the packing dry density can be decreased by the agglomerating effect of fine particles and wall effect of the container. For the binary-size, ternary-size and multi-size mixtures, there is an optimal particle size distribution corresponding to the peak packing dry density, which was found to be closely related to the particle size ratio of the finest size class to the coarsest one. The effects of particle size ratio and distribution can be interpreted by the ‘net positive effect’ representing the competition between the positive effects (filling and occupying effects) and the negative effects (loosening, wall, wedging and agglomeration effects) of particle interactions.

Effect of particle size ratio on microstructure and mechanical properties of aluminum matrix composites reinforced with Zr48Cu36Ag8Al8 metallic glass particles

Aluminum matrix composites reinforced with Zr48Cu36Ag8Al8 glassy particles were synthesized by powder metallurgy using reinforcement particles larger than the matrix. The effect of the matrix to reinforcement particle size ratio (PSR) on the microstructure and mechanical properties was studied. The results show that high densification (relative density > 98%) was achieved and the glassy particles retained the amorphous structure in all the composites. Quantitative particle distribution analysis in the three-dimensional space indicated that the homogeneity distribution index decreases with reducing PSR. The findings suggest that a ratio of 1/3 ≤ PSR ≤ 1 can be used to obtain composites with rather homogenous distribution of the reinforcement particles. Both compressive and tensile yield strengths of the composites are not sensitive to the PSR change (in the range of 1/3–1/6), whereas the ultimate tensile strength and the ductility are significantly reduced with decreasing PSR; this behavior is accompanied by the change of the fracture mode. The experimental yield strength was found to be consistent with the quantitative strengthening mechanism calculations, and indicated that the reduced matrix ligament size, the thermal mismatch and load bearing are the main strengthening contributions.

Dynamic characteristics of binary sphere mixtures under air impact

This paper presents a numerical study on the packing densification process of binary sphere mixtures under air impact using a combined computational fluid dynamics and discrete element method (CFD-DEM) scheme. The effects of particle size ratio (PSR) on the force and stress characteristics including the depth-averaged normal force, probability density function (PDF) of normal forces, distributions of strong forces, mean stress distribution in the axial cross-section, and depth-averaged mean stress for various contact types, are comprehensively analyzed. In addition, the distribution of fluid-particle interaction forces is also discussed to explain the densification mechanism during air impact. The results reveal that the force and stress characteristics are significantly affected by both PSR and air impact. For each PSR, the packing density increases with the gas inlet velocity to a maximum and then decreases. Meanwhile, both the depth-averaged normal force and the mean stress in initial packing increase linearly with the depth, while the relationship between the depth-averaged normal force or mean stress and the depth is in power law growth in the final packing after air impact. The contact type of L-S (L-large sphere, S-small sphere) plays a leading role in the PDF of normal forces, while the effects of S-S contact type on the packing system is weak. Furthermore, apart from the L-L contact, the strong force percentage of other contacts increases after air impact densification. The air impact can effectively improve the uniformity of the normalized mean stress distribution for the packing of binary mixtures. Finally, the distribution of fluid-particle interaction forces demonstrates that the packing can be densified by obvious rearrangement of small particles for adjacent pore filling, and this trend will become more apparent with the increase of PSR.

Effect of particle size ratio and contribution of particle size fractions on micromechanics of uniaxially compressed binary sphere mixtures

This paper is an extension of the recent work of Wiącek (Granul Matter 18:42, 2016), wherein geometrical parameters of binary granular mixtures with various particle size ratio and contribution of the particle size fractions were investigated. In this study, a micromechanics of binary mixtures with various ratio of the diameter of small and large spheres and contribution of small particles was analyzed using discrete element simulations of confined uniaxial compression. The study addressed contact normal orientation distributions, global and partial contact force distributions and pressure distribution in packings of frictional spheres. Additionally, the effect of particle size ratio and contribution of particle size fractions on energy dissipation in granular mixtures was investigated. The particle size ratio in binary packings was chosen to prevent small particles from percolating through bedding. The bimodality of mixtures was found to have a strong effect on distribution of contact normal orientation and distribution of normal contact forces in binary mixtures. Stress transfer in binary packing was also determined by both, particle size ratio and volume fraction of small particles. Dissipation of energy was higher in mixtures with higher particle size ratios and decreased with increasing contribution of small spheres in system.

Effective elastic properties and pressure distribution in bidisperse granular packings: DEM simulations and experiment

The effective elastic properties and pressure distribution in granular mixtures depend on both, material and geometric properties of particles. Using the discrete element method, the effect of geometric and statistical factors on the mechanical response of binary packings of steel beads under uniaxial confined compression was studied. The ratio of the diameter of small and large spheres in bidisperse mixtures was chosen to prevent small particles from percolating through bedding. The study addressed lateral-to-vertical pressure ratio and effective elastic modulus of particulate beds. The bimodality of mixtures was found to have a strong effect on the packing density of samples with the ratio between large and small particles larger than 1.3; however, no effect of particle size ratio and contribution of particle size fractions on the distribution of pressure and elasticity of bidisperse packings was observed. Regardless on the composition of mixtures, the lateral-to-vertical pressure ratio followed the same paths with increasing contribution of small particles in mixtures. The effective elastic modulus of granular packings increased with increasing compressive load and was slightly affected by geometric and statistical factors. The experimental data followed the same trend of the DEM predictions; however, only qualitative agreement between numerical and experimental results was obtained. The discrete element method generated packings with smaller density and overpredicted pressure ratios and elastic parameters of mixtures.