Particle Shape Characteristics Research Articles

A comparative study of morphological characteristics of medium-density fiberboard dust by sieve and image analyses

Sanding dust is the main source of dust emission during the manufacturing process of medium-density fiberboard (MDF), and particle size and shape characteristics are the fundamental properties influencing its environmental influence and handling behaviors. However, there are few deep and comprehensive researches on the morphology of MDF sanding dust. In this study, the morphological characteristics of MDF sanding dust were explored by sieve and image analyses. It was found that more than 95% of MDF sanding dust was inhalable particles smaller than 100 μm, which poses a considerable potential risk to human health and safety, especially with the presence of other chemical constituents. The particle size span of MDF dust was relatively wide though the particle surface texture was quite uniform. The particle geometric proportion represented by aspect ratio decreased markedly with the reduction of particle size. The larger particles presented typical anisotropic structure, while the smaller ones showed homogeneous appearance, indicating quite complex handling behaviors. In addition, image analysis was found to provide a better insight into the morphological characteristics of MDF sanding dust compared to sieve analysis, and could be a promising dust morphology evaluation technology.

Shear behaviours of cohesionless mixed soils using the DEM: The influence of coarse particle shape

The coarse particles in mixed soils can be cobbles or gravels, with the main difference being their roundness (an indicator describing particle shape characteristics at an intermediate scale). The influence of coarse particle shape (i.e., roundness) on the macroscopic and microscopic shear behaviours of cohesionless mixed soils with various fines contents (FCs) was investigated via the discrete element method in this study. The shapes of coarse particles were formed using the rotation-invariant spherical harmonic method proposed by previous investigators. An equation was proposed to predict the initial void ratios of samples in this study. A decrease in the roundness of coarse particles can increase the peak friction angle (FC≤40%) and critical friction angle (FC≤30%). As the roundness of coarse particles decreases, the peak dilatancy angle initially increases and then decreases (FC≤20%). Furthermore, it was found that the roundness of coarse particles hardly affects the classification of cohesionless mixed soils, as determined by probing the percentage contributions of coarse–coarse, coarse–fine, and fine–fine contacts. When cohesionless mixed soils change from an underfilled structure to an interactive-underfilled structure at the critical state, the main forms of coarse–coarse contacts were discovered. Additionally, the force-fabric anisotropy mechanisms of the influences of the roundness and rolling resistance coefficient of coarse particles on the shear strengths of cohesionless mixed soils were found to be different.

On the Effect of Modified Carbohydrates on the Size and Shape of Gold and Silver Nanostructures.

Gold (Au) and silver (Ag) nanostructures have widespread utilization from biomedicine to materials science. Therefore, their synthesis with control of their morphology and surface chemistry have been among the hot topics over the last decades. Here, we introduce a new approach relying on sugar derivatives that work as reducing, stabilizing, and capping agents in the synthesis of Au and Ag nanostructures. These sugar derivatives are utilized alone and as mixture, resulting in spherical, spheroid, trigonal, polygonic, and star-like morphologies. The synthesis approach was further tested in the presence of acetate and dimethylamine as size- and shape-directing agents. With the use of transmission electron microscopy (TEM), selected area electron diffraction (SAED), x-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible (UV-vis) absorption spectroscopy techniques, the particle size, shape, assembly, aggregation, and film formation characteristics were evaluated. NPs’ attributes were shown to be tunable by manipulating the sugar ligand selection and sugar ligand/metal-ion ratio. For instance, with an imine side group and changing the sugar moiety from cellobiose to lactose, the morphology of the Ag nanoparticles (NPs) transformed from well dispersed cubic to rough and aggregated. The introduction of acetate and dimethylamine further extended the growth pattern and morphological properties of these NPs. As examples, L5 AS, G5AS, and S5AS ligands formed spherical or sheet-like structures when used alone, which upon the use of these additives transformed into larger multicore and rough NPs, revealing their significant effect on the NP morphology. Selected samples were tested for their stability against protein corona formation and ionic strength, where a high chemical stability and resistance to protein coating were observed. The findings show a promising, benign approach for the synthesis of shape- and size-directed Au and Ag nanostructures, along with a selection of the chemistry of carbohydrate-derivatives that can open new windows for their applications.

Quantitative evaluation for shape characteristics of aggregate particles based on 3D point cloud data

The aggregate with good shape characteristics are conducive to the formation of the internal structure of asphalt pavement and have an important impact on the pavement performance. In order to quantify the aggregate shape characteristics more comprehensively, the quantitative evaluation method for the shape of aggregate particles based on 3D point cloud data was proposed. Basalt, granite and limestone aggregates with size of 9.5 mm, 13.2 mm and 16 mm were obtained by screening. Each type of aggregates was divided into five different shapes of the tetrahedron, pentahedron, hexahedron, elongate and flake. The image acquisition system based on Gocator 3D intelligent sensor was used to collect 3D point cloud data of the aggregates. The noise in the 3D point cloud data collected was removed by the cascade filtering method and then the greedy triangulation algorithm was used to reconstruct the 3D aggregate digitized surface. Finally, the characteristic parameters such as length, width, height, volume and the maximum diameter of the 3D convex hull were extracted from the reconstructed aggregate particles, and the shape indexes of the aggregate, such as the isometric ratio, flakiness ratio, sphericity and roundness indexes, were calculated based on the extracted characteristics. The experimental results show that the 3D shape index of road aggregates proposed in this paper can be used for the comprehensive quantitative evaluation of the morphological characteristics of aggregates with different lithology, particle sizes and shapes. It is instructive to improve the performance of the asphalt mixture and study the aggregate gradation.

Influence of particle size distribution, test time, and moisture content on sandy stratum LCPC abrasivity test results

This paper focuses on the influence of particle size distribution, test time, and moisture content on the Laboratoire Central des Ponts et Chaussees (LCPC) abrasivity coefficient (LAC). Image analysis and X-ray diffraction were used to analyze the particle shape characteristics and equivalent quartz content (EQC) of a sandy stratum. The test results show no significant differences in the shape characteristics and EQC of particles with different diameters obtained from the same sandy stratum. For the same EQC, the main factors affecting the LAC are particle size distribution, test time, and moisture content. An optimized effective size (ESop) index was established to represent different particle size distributions. The test results showed that the ESop index is more accurate than other indices in determining the LAC of soil samples, and the LAC had a linear relationship with the ESop index. Soil samples with moisture content less than the saturated moisture content have an LAC larger than that of a dry soil sample, and soil samples with moisture content greater than the saturated moisture content have an LAC similar to that of a dry soil sample. The influence of test time on the LAC of the soil samples could be divided into two stages, where the first and second stages are represented by a quadratic function and a linear function, respectively.

Comparison of Various Particle-Size Distribution-Measurement Methods

Summary Sieve analysis, sedimentation, and laser diffraction (LD) have been the methods of choice in determining particle-size distribution (PSD) for sand control design. However, these methods do not provide any information regarding the particle shape. In this study, we introduce the application of dynamic image analysis (DIA) to characterize particle sizes and shape descriptors of sand-bearing formations. DIA, which is an advanced method of particle size and shape characterization, along with other PSD measurement methods, including sieving, sedimentation, and LD, were used to study size and shape variations of 372 unconsolidated formation sand samples from North America, Latin America, and the Middle East. Different methods were compared in the estimation of PSD and fines content, which are the primary factors important in sand-control design. Through minimizing the sampling and measurement errors, the deviation between different PSD measurement techniques was attributed solely to the shape of the particles and the amount of fine fraction. For fines-content measurement, the values obtained through Feret min parameter values (the minimum size of a particle along all directions) calculated by DIA and sieving measurement are comparable within a 5% confidence band. The deviation between the results of different methods becomes more significant by increasing fines content. Moreover, this deviation increases for less isodiametric grains. The fines and clay content show higher values when measured by any wet analysis. LD also tends to overestimate the fines fraction and underestimate silt/sand fraction compared with other dry techniques. By comparing the deviation of the DIA and sieving at standard mesh sizes, an algorithm has been developed that chooses the equivalent sphere sizes of DIA with minimum deviation from sieving. This study performs several measurements on formation sands to illustrate the real advantage of the new methods over traditional measurement techniques. Furthermore, particle-shape descriptors were used to explain the deviation between the results of different PSD measurement methods.

Liming Requirements of Greenhouse Peat-based Substrates Amended with Pine Wood Chips as a Perlite Alternative

Processed loblolly pine (Pinus taeda) wood has been investigated as a component in greenhouse and nursery substrates for many years. Specifically, pine wood chips (PWCs) have been uniquely engineered/processed into a nonfibrous blockular particle size suitable for use as a substrate aggregate. The objective of this research was to compare the dolomitic limestone requirements of plants grown in peat-based substrates amended with perlite or PWC. In a growth trial with ‘Mildred Yellow’ chrysanthemum (Chrysanthemum ×morifolium), peat-based substrates were amended to contain 0%, 10%, 20%, 30%, 40%, or 50% (by volume) perlite or PWC for a total of 11 substrates. Substrates were amended with dolomitic limestone at rates of 0, 3, 6, 9, or 12 lb/yard3, for a total of 55 substrate treatments. Results indicate that pH of substrates amended with ≥30% perlite or PWC need to be adjusted to similar rates of 9 to 12 lb/yard3 dolomitic limestone to produce similar-quality chrysanthemum plants. In a repeated study, ‘Moonsong Deep Orange’ african marigold (Tagetes erecta) plants were grown in the same substrates previously formulated (with the exclusion of the 50% ratio) and amended with dolomitic limestone at rates of 0, 3, 6, 9, 12, or 15 lb/yard3, for a total of 54 substrate treatments. Results indicate a similar dolomitic limestone rate of 15 lb/yard3 is required to adjust substrate pH of 100% peatmoss and peat-based substrates amended with 10% to 40% perlite or PWC aggregates to the recommended pH range for african marigold and to produce visually similar plants. The specific particle shape and surface characteristics of the engineered PWC may not be similar to other wood products (fiber) currently commercialized in the greenhouse industry, therefore the lime requirements and resulting substrate pH may not be similar for those materials.

Instability of loose sand in constant volume direct simple shear tests in relation to particle shape

Post-peak flow instability of six sands notably different in terms of average particle shape characteristics, gradation, and mineralogy was investigated. Tests were carried out under constant volume condition using a NGI-type direct simple shear apparatus. The testing program covers wide ranges of initial void ratios and vertical effective stresses. Experimental findings confirm that the critical state parameters of the test sands depend strongly on the average particle morphologic characteristic factors. For specimens in loose state, it is shown that stress ratio at the onset of flow instability, normalized constant volume peak shear strength, brittleness index, and the normalized pore water pressure of the tested sands are interrelated with the particles’ morphologic factors.

Investigation on the morphological and mineralogical properties of coarse aggregates under VSI crushing operation

ABSTRACT In this paper, the role of crushing operation on the cubical controlling features of coarse aggregates, and its influence on the shape distribution characteristics of aggregates (i.e. angularity, sphericity, and flatness & elongation ratio) were investigated through the second version of Aggregate Image Measuring System (AIMS II). Three types of aggregate from different origins were chosen and crushed by the vertical shaft impactor (VSI) with fixed rotational speed. The results indicate that the rotation speed of VSI is influenced by the input power of the machine to the particle sizes, and higher speed leads to more cracks on aggregates during the crushing process. By using X-ray diffraction (XRD), the aggregate samples from different origins and mineral compositions were analysed under the same working operation of crusher. Besides that, the correlation between particle shape characteristics influenced by the mineralogical composition, and their collision behaviours have been discussed according to the tested results. A recommendation for optimal operation of VSI on crushing granite aggregates is given based on this study. Whereas, the cubical condition of aggregates and energy saving factors were taken into account. Furthermore, petrographic analyses were imposed to correlate particle mineralogy to its collision behaviour during crushing.

Shape descriptors - settling characteristics of irregular shaped particles

Shape descriptor is a concise yet informative representation to address challenging issues in areas as diverse as engineering, medicine and biology. The prediction of settling velocity and drag coefficient of non-spherical shaped particles as close as possible to their actual behavior has been an interest to engineering community. Often, correlations developed for predicting settling velocity do not accomplish the estimation of the drag coefficient. The solid particle shape characteristics need to be assessed with definitions of NRep and Ar suitably. Terfous et al. (2013, Predicting the Drag Coefficient and Settling Velocity of Spherical Particles. Powder Technology. 239:12–20) presented a direct prediction of settling velocity for a spherical particle correlating NRep and Ar with good accuracy over a wide range of NRep. In this paper, appropriate scaling factors are suggested to represent NRep and Archimedes number and compared with data from in-house experiments and from published literature. The prediction is found to be in fair agreement with data from published work (cuboid and cylinders with various aspect ratio) and experimental data generated in-house with irregular shaped solid particles viz., sand, plastic, coal, raagi (Millets) and mustard seeds.HighlightsEstimation of settling velocity of different irregular shaped particles viz., sand, plastic, coal, mustard, raagi etc.A modified correlation to predict the settling velocity of irregular shaped particle by including shape descriptors viz, circularity, volume fraction, volume projected area diameter.The average error between the predicted and experimental data is found to be around 8.3%.

Prediction Model of Minimum Void Ratio for Various Sizes/Shapes of Sandy Binary Mixture

The minimum void ratio is a fundamental physical index for evaluating particle properties in soil mechanics, ceramic processing, and concrete mixes. Previous research found that both particle size distribution and particle shape characteristics would affect minimum void ratio, while the current research generally uses a linear model to estimate the minimum void ratio of a binary mixture, ignoring quantitative effect of particle shape on the minimum void ratio. Based on a study of binary mixtures of natural sand from three different origins and iron particles of two different shapes, this paper analyzes the influence factors of the minimum void ratio, and a quadratic nonlinear model is proposed for estimating the minimum void ratio of binary mixture. The model contains only one undetermined coefficient, a, the value of which is correlated to the particle sphericity, particle size, and particle size ratio. A theoretical calculation formula for the coefficient a is proposed to quantitatively analyze the effects of these three factors on the size of the parameters. In the end, the model is used to estimate the minimum void ratios of sand and substitute particles from different producing areas; the average difference between the estimated values and the fitted values is about 2.03%, suggesting that the estimated values of the model fit well with the measured data.

Dust Content and Adhesion Characteristics of Five Corn Samples

HighlightsThe corn sample and centrifuge speed interactions were statistically significant predictors of dust generation.Attachment strengths of dust particles were calculated, with forces ranging from less than 4.6 × 10-10 N to 2.1 × 10-8 N.A sequential centrifuge experiment indicated a bimodal distribution of adhesion forces.Abstract. Grain dust explosions are a constant threat to the grain handling industry. Explosions occur when dust accumulates beyond the minimum explosion concentration in a confined area and is exposed to an ignition source. Handling and grain unloading conditions that generate dust, the minimum explosive dust concentration, overpressure from an explosion, and other factors that lead to grain dust explosion are well documented in the literature. The adhesion force that holds grain dust particles to the grain itself is an important factor in better understanding and mitigating dust separation from grain kernels and the resulting dust cloud generation. However, that adhesion force, how it is affected by grain quality, and how it is influenced by particle factors such as size and shape has not been adequately researched. A centrifuge separation technique was used to study the adhesion forces of grain dust. Results showed large variability in dust concentration between the five corn samples tested in this study. The dust particle attachment strength ranged from less than 4.6 × 10-10 N to 2.1 × 10-8 N. Only the sample and centrifuge speed interaction had a statistically significant effect on dust concentrations recovered at a 5% confidence limit. Under repeated centrifugations, the dust removed showed a bimodal distribution of attachment strengths, with three of four samples tested showing a local minimum at 2000 rpm, and the other at 3000 rpm. This study improves the understanding of the fundamental attachment strength behind dust separation from grain kernels. Investigating the size, shape, and surface characteristics of dust particles with varying attachment strengths is important to further understand their adhesion and separation mechanisms. Keywords: Adhesion strength, Dust explosion, Dust mitigation, Grain dust, Grain handling.

Discrete Element Modeling and Simulation of Soybean Seed Using Multi-Spheres and Super-Ellipsoids

The accuracy of particle shape characterization is the key to the study of particle dynamics. This study proposes two modeling methods, super-ellipsoid approach (SE) and multi-sphere approach (MS), to describe the discrete element method (DEM) model of soybean seeds with the goal of improving the accuracy of the discrete element analysis model of soybean seeds. The accumulation process, flow behavior, and mixing characteristics of soybean seeds were studied through experiments and DEM simulation. Three comparative verification tests were carried out to compare the accuracy and potential similarity of the SE particle model and the MS particle model: (1) angle of repose experiment; (2) slope screening experiment; and (3) horizontal rotating cylinder experiment. The simulation and experimental results indicated that when compared with the MS particle model, the soybean seed model established using the super-ellipsoid approach can make the described particle shape more accurate, and also reproduce the accumulation process, flow behavior, and mixing characteristics of soybean seeds more accurately. For the multi-sphere approach, the calculation cost for approximating the DEM model of soybean seeds can be saved when the number of sub-spheres is less, but the accuracy of the particle model will be reduced at the same time. In this paper, the DEM model established using the super-ellipsoid approach can accurately simulate the real movement of soybean seeds. Therefore, the model can provide a new numerical calculation method for the simulation of the particle system in the structure of agricultural machinery.

Dual-beam interferometric particle imaging for size and shape characterization of irregular coal micro-particle: Validation with digital inline holography

The size and shape characterization of irregular particles is of great significance in the comprehensive understanding of many natural and industrial processes. The dual-beam interferometric particle imaging (DIPI) technique is adapted from a dual-beam backward illumination configuration of interferometric particle imaging to access the size and 2D shape of an irregular particle from its interferogram. An experimental setup combining the digital inline holography (DIH) and DIPI techniques characterizes the same projection of the same particle with a color camera, permitting the accuracy evaluation and validation between these two techniques. The comparison results show a good agreement between the 2D-Fourier transform of DIPI interferogram and the 2D-autocorrelation of DIH reconstructed in-focus image. The DIH gives the reference result for the size measurement of the particles, and we observe a maximum difference as low as 9% with the DIPI measurement. The backward arrangement of the dual-beam interferometric particle imaging technique facilitates its further instrumental development and application to a variety of real circumstances, e.g., solid fuel particles and ice crystals.

Probabilistic characterization and simulation of realistic particle shape based on sphere harmonic representation and Nataf transformation

Significant commitment of cost, man power, and time are often required for characterizing particle morphology of granular materials based on X-ray micro-computed tomography (μCT) scanning and image processing. As a result, only a small portion of particles can be scanned, leading to uncertainty in characterizing realistic particle shape. This paper develops a probabilistic method to characterize and simulate sand particle shape based on Sphere Harmonic (SH) analysis, where Nataf transformation is used to construct the joint probability distribution of SH shape descriptors and to generate their random samples for reconstructing virtual particles. The proposed approach was applied to characterizing and simulating particle shapes of Leighton Buzzard sand (LBS), and these simulated particles were used as clump templates for discrete element method to account for effect of realistic particle shape. It was shown that the proposed approach properly characterizes and simulates the particle shape of LBS in a probabilistic manner.

Analysis of loess sediment texture in Golestan province according to the microstructure parameters

This study was performed to recognize the loess texture in Golestan Province, Iran using the microstructure analysis according to the electron microscopic images. Loess microstructure study allows for investigating the characteristics of particle shape, fabric, cement and porosity in microscopic images. In recent years, computer analysis has been replaced with manual calculation due to its high speed, precision and ease of use. Since the scanning electron microscope (SEM) digital image analysis method can quantitatively determine the loess microstructure and identify the microstructure changes, it was used to analyze the loess texture. The obtained results showed that the loess microstructure changed from north and northeast to south and southwest of Golestan Province. According to microstructural and sedimentology parameters, Golestan Province loess can be divided into 4 zones. The results also showed that microstructural study of loess sediments in Golestan Province could be a useful tool for loess zoning and separating loess sediments from loess-like deposits.

Experimental Study on Manufactured Sand Shape Detection by Image Method

Abstract Manufactured sand often has granules with uneven shapes, which affects the quality of concrete. Hence, the detection of the shape of manufactured sand is important to ensure the quality of concrete. In this article, an image analysis system is used to detect the particle shapes, and the flow time aggregate angularity test is used as a reference to study the correlation between several particle shape characterization parameters and the flow time method. The result shows that the equivalent ellipse axial ratio Ae is the best index for evaluating the uniformity of manufactured sand shape. Repeatability tests with single-grade and graded materials showed that the maximum repeatability errors for three types of single-grade material are 0.5 %, 2.52 %, and 2.97 %, respectively, and the maximum repeatability error for the graded material is 0.85 %. When the particle shape is closer to a sphere, the repeatability of the measurements is high. Therefore, the image method particle shape detection system can meet the requirements for manufactured sand shape detection and effectively monitor the quality of manufactured sand for use as aggregate in concrete.

An Experimental Study on Effect of Boundary Condition on Particle Damage in Shear Zone of Crushed Sand

AbstractVarious factors influence particle breakage in the shear zone of silica sands, including particle shape characteristics, loading path, shear displacement, normal load, initial density, and boundary conditions. The present study focuses on particle breakage occurring in the shear zone of a crushed silica sand under shear loading. Several ring shear tests were conducted to measure shear stress‐displacement response of a sand. Grain‐size distribution curves of the original sand (prior to shearing) and the sheared sand from the shear zone are then compared. The mechanism of particle breakage is determined by a thorough examination of particle damage under “constant normal load” and “constant volume” tests, considering both loose and dense samples. The results show that void ratio is the dominant factor in particle breakage. On the other hand, it is observed that particle breakage resulting from particle shape properties accrues within the initial loading stages. It is observed that the boundary condition also affects the magnitude of particle breakage; that is, particle damage under “constant normal load” boundary condition is found to be significantly higher than that under “constant volume” condition for the same initial normal stress and void ratio.

Shape Characterization of Subvisible Particles Using Dynamic Imaging Analysis.

Protein aggregates and subvisible particles (SbvP), inherently present in all marketed protein drug products, have received increasing attention by health authorities. Dynamic imaging analysis was introduced to visualize SbvP and facilitate understanding of their origin. The educational United States Pharmacopeia chapter <1787> emphasizes that dynamic imaging analysis could be used for morphology measurements in the size range of 4-100 μm. However, adequate morphology characterization, as suggested in the United States Pharmacopeia <1787> proposed size range, remains challenging as nonspherical size standards are not commercially available. In this study, a homogenous and well-defined nonspherical particle standard was fabricated and used to investigate the capabilities of 2 dynamic imaging analysis systems (microflow imaging (MFI) and FlowCAM) to characterize SbvP shape in the size range of 2-10 μm. The actual aspect ratio of the SbvP was measured by scanning electron microscopy and compared to the results obtained by dynamic imaging analysis. The test procedure was used to assess the accuracy in determining the shape characteristics of the nonspherical particles. In general, dynamic imaging analysis showed decreasing accuracy in morphology characterization for 5 μm and 2 μm particles. The test procedure was also capable to compare and evaluate differences between the 2 dynamic imaging methods. The present study should help to define ranges of operation for dynamic imaging analysis systems.

Particle obstruction and crushing of dredged calcareous soil in the Nansha Islands, South China Sea

The bearing capacity of the dredged calcareous soil in the Nansha Islands, South China Sea typically exceeds that of terrigenous dredger fill. Furthermore, the shear strength of calcareous soil exceeds that of siliceous sand under identical conditions. It is mainly caused by the interparticle obstruction between calcareous soil particles. To explore the obstruction mechanism of calcareous soil particles, a series of triaxial tests were performed on calcareous soils under both consolidated undrained (CU) and consolidated drained (CD) conditions, respectively. Particle shape characteristics and particle crushing were also investigated to study the formation mechanism of obstruction force. Test results indicate that irregular particle shape is the prerequisite for the emergence of particle obstruction in calcareous soils. A simple obstruction-dilatation model was developed to describe the relationship among particle obstruction, dilation and particle crushing. The obstruction force varies greatly during the shearing process, which is mainly influenced by particle size and stress level. Under low confining pressure, particle obstruction results in dilatation and increases internal friction angle. In contrast, obstruction causes particle breakage, increases the apparent cohesion, and ultimately decreases the effective internal friction angle under high confining pressures. The particle obstruction of calcareous soil noticeably improves shear strength. Therefore, the effect of particle obstruction on strength should be considered in coral reef engineering design work.