Effect Of Grain Size Distribution Research Articles

Thermal conductivity of WC: Microstructural design driven by first-principles simulations

The relationships between the microstructure and the thermal conductivity of binderless WC have been quantified, considering crystal orientation, isotopic abundance, porosity, and grain size. A significantly higher conductivity is predicted in the out-of-plane (c-axis) direction vs. the in-plane (a-axis) direction, using first principles simulations. Isotopic enrichment of the tungsten sublattice is predicted to increase conductivity, e.g., by a factor of 4–5 in the absence of boundary scattering. The results suggest that for an isotopically pure single crystal a thermal conductivity exceeding 1000 W m−1 K−1 may be achievable normal to the basal plane. The conductivity of samples with various porosities could be well fit by a minimum surface area (exponential) model, with a porosity exponent of b = 4.4. Experiment and simulation show a strong grain size dependence to conductivity below 1 µm, with a saturation beyond ∼10 µm. The experimental plateau values for κ were ∼45 % lower than those of the simulations due to deviations from perfect stoichiometry. We also find a higher scattering coefficient in the experiments, likely due to effects of grain size distribution and elongation. Our study clarifies the physical origin of disagreeing literature reports as being predominantly due to grain boundary scattering and enables microstructural design for thermally demanding environments.

EXPERIMENTAL STUDY ON THE FRACTURE CONDUCTIVITY IN SHALE OIL PRODUCTION

Unconventional oil and gas resources, such as shale oil and gas, are gradually attracting great attention from all countries of the world. Horizontal drilling and large-scale hydraulic fracturing technology are used to efficiently extract oil from shale formation. Effective placement of the proppant in the fractures and high long-term conductivity are the keys to solve the problems of oil well flow rate increase in shale oil and gas fields. In this work, the sieve analysis method and FCMS-V fracture conductivity determination device, as well as scanning electron microscope are used. They are used to experimentally investigate the filtration characteristics of hydraulic fracturing fractures and establish the key factors affecting the filtration characteristics. The object of the study is the core of the oil-saturated DG shale formation of Songliao Basin. Also in this paper, the indentation and crushing mechanism of proppant under reservoir conditions is studied. The influence of various factors was evaluated qualitatively and quantitatively. The following studies were conducted: the effect of sand granule size on conductivity, the effect of grain size distribution on conductivity, the effect of proppant concentration on conductivity, the effect of fracture closure pressure on conductivity, and the effect of proppant indentation on conductivity. The granule sizes of the proppant used range from 30/50 to 70/140 mesh. Proppant concentration: 2,5; 5; 10 kg/m2. Ratios of granule sizes for used mixtures: 1:1:1, 1:2:7, 1:4:5.And crack clamping pressure from 20 to 40 MPa. As a result of the study, dependences of initial and long-term fracture conductivity on clamping pressure, granulometric composition of proppant and its concentration were obtained. Using a scanning electron microscope, the degree of indentation and crushing of proppant under reservoir conditions in two media, namely shale core and steel plates, was visually evaluated. The results of experimental studies can be used to optimize the shale oil development system and have scientific and practical significance for shale oil production in continental deposits.

Probing the impact of grain size distribution on the deformation behavior in fine-grained austenitic stainless steel: A critical analysis of unimodal structure versus bimodal structure

This study investigated the effect of grain size distribution on the deformation behavior in fine-grained (FG) austenitic stainless steels (γ-SSs). Commercial Cr–Mn–N γ-SS was selected as the coarse-grained (CG) specimen, which was cold rolled and then annealed at 1000 °C for 60 s and 700 °C for 3600 s to obtain FG specimens with similar grain sizes but different grain size distributions. The CG specimens annealed at 1000 °C for 60 s and 700 °C for 3600 s were referred to as unimodal-FG and bimodal-FG specimens, respectively. The tensile properties revealed that the yield strength was enhanced from 383 MPa to 685 MPa when the grain size was refined from CG (10.7 μm) to FG (∼1.8 μm). Moreover, the bimodal-FG specimen exhibited a higher total elongation of 48% than 36.5% for the unimodal-FG specimen. Transmission electron microscopy, electron backscatter diffraction and X-ray diffraction were used to identify the microstructural characteristics during tension. The results indicated that the main deformation mechanisms of γ-SSs specimens during tension were dislocation generation and accumulation at the initial stage, deformation twinning at the intermediate stage, and deformation-induced martensite (DIM) at the final stage. Compared with the unimodal-CG counterpart, grain refinement in the unimodal-FG specimens restricted the formation of DIM due to the increased austenite stability. A newly discovered phenomenon was that the bimodal-FG specimens promoted the formation of geometrically necessary dislocation (GND) and DIM compared to the unimodal-FG, which was due to the uneven deformation in grains located on hetero-boundaries (HBs). Moreover, the bimodal-FG specimen was preferentially formed DIM on HBs, especially in the smaller grains side rather than inside larger grains due to the higher stress concentration in smaller grains.

Effects of grain size distributions on scattering attenuation of elastic waves in polycrystalline materials

Effects of grain size distributions on scattering attenuation of elastic waves in polycrystalline materials

Fundamental study on the effect of grain size distribution on angle of repose

In this study, the authors developed a new sidewall velocity-controlled cylindrical angle of repose measurement apparatus that can capture images of a sand heap continuously using two orthogonal cameras in order to reduce the cost of photography. The developed apparatus was used to measure the angle from formation to repose of sand heap using different grain sizes distribution and to assess the effect of grain size distribution on the angle of repose. The formation process of the sand heap was continuously measured using the experimental apparatus, and it was found that the sand heap became steady state when it reached a certain height. It is inferred that the angle of repose measured in a stationary state indicates the inclination angle of the sand heap at a certain point in time, suggesting the possibility of obtaining a highly accurate angle of repose with fewer experiments by using this experimental apparatus to continuously acquire and average the inclination angle of a sand heap in a steady state. For samples with a stepped grain size distribution, the angle of repose was found to be higher than for samples with a gentle grain size distribution at the same 20% grain size D20 and mean grain size D50. It was found that the angle of repose increased logarithmically with increasing coefficient of uniformity. Based on these results, it is clear that for a well-graded sand, it is the grain size rather than the coefficient of uniformity that has an effect on the angle of repose.

Elucidating the process mechanism in Mg-to-Al friction stir lap welding enhanced by ultrasonic vibration

The composite structures/components made by friction stir lap welding (FSLW) of Mg alloy sheet and Al alloy sheet are of wide application potentials in the manufacturing sector of transportation vehicles. To further improve the joint quality, the ultrasonic vibration (UV) is exerted in FSLW, and the UV enhanced FSLW (UVeFSLW) was developed for making Mg-to-Al dissimilar joints. The numerical analysis and experimental investigation were combined to study the process mechanism in Mg/Al UVeFSLW. An equation related to the temperature and strain rate was derived to calculate the grain size at different locations of the weld nugget zone, and the effect of grain size distribution on the threshold thermal stress was included, so that the prediction accuracy of flow stress was further improved. With such modified constitutive equation, the numerical simulation was conducted to compare the heat generation, temperature profiles and material flow behaviors in Mg/Al UVeFSLW/FSLW processes. It was found that the exerted UV decreased the temperature at two checking points on the tool/workpiece interface from 707/671 K in FSLW to 689/660 K in UVeFSLW, which suppressed the IMCs thickness at Mg-Al interface from 1.7 µm in FSLW to 1.1 µm in UVeFSLW. The exerted UV increased the horizontal materials flow ability, and decreased the upward flow ability, which resulted in the increase of effective sheet thickness/effective lap width from 2.01/3.70 mm in FSLW to 2.04/4.84 mm in UVeFSLW. Therefore, the ultrasonic vibration improved the tensile shear strength of Mg-to-Al lap joints by 18 %.

Lattice Boltzmann Simulations of the Dynamic Adsorption of Gas in Porous Media: Effect of Grain Size Distribution

Lattice Boltzmann Simulations of the Dynamic Adsorption of Gas in Porous Media: Effect of Grain Size Distribution

Effect of Grain Size Distribution on Pore Size Distribution Characteristics in a Conglomerate Reservoir from an Alluvial Fan Via Artificial Rock Approach

Summary Conglomerate is characterized by a multiscale grain stacking structure and various pore size distribution modes (PSDMs), significantly affecting multiphase fluid movement and transport in porous media. The multimodal structure and complicated PSDM are related to grain size distribution. However, the relationship between grain size distribution and pore structure characteristics remains unclear, which makes it hard to investigate using natural rocks affected by a single factor. Herein, a newly developed full-pore-scale artificial rock approach was used in this work to provide the ideal samples for experimental research. A bimodal distribution model was adopted to characterize the grain size distribution features quantitatively. Furthermore, the relationship between lithofacies, permeability, and PSDM was analyzed. The results demonstrate that grain size distribution includes coarse grain distribution (CGD) and fine grain distribution (FGD). As the average value of FGD increases, the permeability of conglomerate and sandstone have different decreasing trends. The increases in the grain size difference between CGD and FGD can decrease the most frequent and average pore radius, while the PSDM of conglomerate transforms from a steep peak shape to a hill shape. Furthermore, PSDM relates to permeability and lithofacies in an alluvial fan environment. The maximum permeability of sandstone with PSDM of hill shape is about 40 md while that of conglomerate is about 70 md. The grain and pore size distribution of artificial rocks is highly similar to that of natural rocks compared with natural rocks within the alluvial fan of Karamay conglomerate reservoirs. The findings are significant for robust determination in reservoir evaluation and development.

Corrigendum: Effect of grain size distribution on the shear properties of sand

Corrigendum: Effect of grain size distribution on the shear properties of sand

Dynamics of granular debris flows against slit dams based on the CFD–DEM method: effect of grain size distribution and ambient environments

AbstractEarth surface flows in nature, like debris flows and rock avalanches, have threatened people’s safety and infrastructure during past decades. Though grain size distribution (GSD) has been acknowledged as a crucial characteristic in granular material behaviour, its coupled effects associated with environments on engineering structures such as the slit dam remain unclear. To bridge the gap, this paper reveals the coupled effect of the GSD and ambient environments (i.e. slope angles and saturation conditions) on avalanche/debris flows’ impact on the slit dam using a Computational Fluid Dynamics/Discrete Element Method (CFD–DEM) model. To describe strain-dependent rheological characteristics of debris fluids, the Herschel–Bulkley–Papanastasiou model is implemented in the finite volume method framework. A power grain size distribution law is considered to quantify GSDs, in which a fractal parameter takes charge of GSD types. After model verification with experimental/theoretical results, the impact force against slit dams, granular dynamics and final deposit patterns under a series of ambient circumstances are presented. Taking advantage of the CFD–DEM method, the impact force and kinetic energy induced by fluid and solid phases are discriminated. The contribution of solid and fluid phases to both impact force and dynamics appears to be dependent on GSDs. Accordingly, compared with saturated avalanche flows (i.e. debris flows), slit dams result in higher retaining efficiency when confronted with dry avalanche flows. Regarding a narrow diameter range used in analyses, the grain diameter ratio is then enlarged up to eight to reveal the potential size effect. As for the coupled role of GSDs and slope angles, in contrast to slope angles, the influence of GSD on avalanche flow interaction with slit dams is much smaller. Additionally, provided a narrow diameter range, the effect of GSDs on impact force can be partially attributed to the change in average grain diameter. After presenting the significance of ambience and GSDs to avalanche/debris flows, a series of parametric studies around the effect of fluid grid size, particle shape and the initial porosity of granular samples are discussed, aiming to advance the understanding of their influence in the interactions between debris flows and the slit dam.

Effect of Grain Size Distribution of Soil on Immobilization of Cadmium and Nickel in Contaminated Soil Using Nano Zerovalent Iron: A Factorial Design and Response Surface Methodology Approach

Urban soils get contaminated due to the unscientific disposal of industrial effluents and solid waste, contaminating the soil with heavy metals. Contaminated soils need to be remediated to avoid the ingestion of toxic heavy metals. The immobilization of heavy metals is one of the methods to remediate contaminated soils. The primary purpose of this study was to explore the effect of grain size distribution (GSD) of soil on the efficiency of immobilization of toxic heavy metals in soil when nano zerovalent iron (nZVI) is used to immobilize the metals. Preliminary studies conducted with the 23 factorial design method confirmed that GSD is a significant factor along with the level of contamination and nZVI dosage in the immobilization of heavy metals in soil. Experiments were conducted with cadmium (Cd) and nickel (Ni), the toxic heavy metals, and three soils with different finer particles than 75 µm. Immobilization efficiency was obtained by comparing the leachability of contaminated and treated soil samples using the toxicity characteristic leaching procedure. Reduction in available fraction and variation in the speciation of heavy metals was observed through the sequential extraction procedure. The response surface methodology was adopted for analysis with three levels of GSD, contamination, and nZVI dosage. For Cd, a reduced cubic model was the best fit with a coefficient of determination (R-square) of 0.93, and for Ni, a quadratic model was the best fit with an R-square of 0.92. Both these models were validated experimentally. The efficiency variation followed an optimum curve concerning GSD, contamination level, and the nZVI dosage. For multimetal contamination, the immobilization efficiency gradually decreased from 10% finer to 90% finer soil, both in the case of Cd and Ni. It was observed that for both single metal and multimetal contamination, the interaction between soil and the nZVI plays a vital role in immobilization along with the factors considered.

Effect of grain size distribution of tailings during the formation of technogenic deposit on the fragmentation index

The most important link in the process chain for creating waste-free technology at concentrating plants is to ensure the possibility of using tailings, where the bulk of non-metallic minerals, rare earth minerals or overburden is concentrated. Increasingly, mining enterprises store their waste, forming man-made deposits. Thus at present time, the development of section technogenic deposits containing tailings is becoming a pressing challenge. The characteristic feature of such deposits is the polydispersity of the developed material, which makes it difficult to determine the fragmentation index. Therefore, the objective of this paper is to study the influence of the grain size distribution of tailings on the fragmentation index during the formation of an technogenic deposit, wherein said index affects the performance of mining and transport equipment, as well as the safety of mining operations. This paper is prepared with the application of the method of mathematical analysis, as well as a laboratory method, including determination of the volume of the pore space by displacement of the liquid phase from a container with a polydisperse mixture and measuring of weight indicators. The polydisperse mixture is represented by a fraction of 0–0,2 mm, 0,2–0,8 mm, 0,8–2,0 mm, 2,0–4,0 mm. 4,0–8,0mm, 3,0–12,0mm. An analysis was made of the influence of 5 indicators on the loosening coefficient. As a result of the study, it was found that the main criterion affecting the loosening coefficient is the ratio of coarse to fine class in the mixture, and not the size of the weighted average particle in it, and the smaller this ratio, the lower the loosening coefficient approaches 1. Class 1 reception in subsequent calculations. The results obtained will become the basis for studying the loosening factor in the development of man-made deposits, represented by tailings, and require further improvement of the theoretical foundations and industrial use.

Effect of grain size distribution on the shear properties of sand

In this study, we investigated the effect of particle size distribution on the shear properties of sand. Direct shear tests were conducted using four types of sand samples with different particle size distributions obtained from standard sand produced by Xiamen ISO Co. Ltd. The results show that the influence of particle size distribution on the internal friction angle was significant. Typically, the internal friction angle increases with increasing the coefficient of non-uniformity (Cu) and decreasing the curvature coefficient (Cc). The discrete element results show that the initial particle size distribution significantly affects the porosity, coordination number, and particle slide fraction. In addition, the grey relation analysis revealed that the sliding fraction and coordination number have the greatest correlation with the internal friction angle. The research results of this study help to understand the changes in particle contact, internal stress, and particle sliding during the shear failure process of sand.

Effect of grain size distribution of polycrystalline microstructure on in-plane wave propagation

This paper presents a study on in-plane wave propagation in two-dimensional polycrystalline microstructure with different grain distributions. The numerical simulations are performed using commercial finite element (FE) package and the microstructure is generated using Voronoi tessellation. The different grain distributions are generated using a regularity parameter, α. In-plane wave results in simultaneous P and S waves unlike conventional bulk wave, where only P or S wave is observed. Such in-plane wave propagation resulting from localized excitation is more realistic and has important applications in microstructural flaw detection. Here, an analogy is drawn with seismic wave in heterogeneous geophysical media to understand the in-plane waves in the polycrystalline microstructure. First, the effect of grain distributions on the attenuation and phase velocity behavior of in-plane wave is studied in the low-frequency Rayleigh regime. The numerical simulations are performed for Inconel-600 for grain sizes of 100 and 250 . Then, the numerical model is validated with experimental results using piezoelectric transducers on an Inconel-600 plate. The physical microstructure of Inconel-600 material is observed using a scanning electron microscope. The frequency dependency of attenuation for in-plane waves is close to unity similar to that of seismic wave. The attenuation and phase velocity vary with the change in regularity parameter, α. Additionally, it is observed that the scattering of P wave is higher than that of S wave during in-plane wave propagation, resulting in higher attenuation of P wave. Finally, an exponential expression is established between regularity parameter and attenuation, which will help in characterizing and predicting the grain distribution inversely.

Reply to the discussion by Dallo on “Updated skeleton void ratio for gravelly sand mixtures considering effect of grain-size distribution”

Reply to the discussion by Dallo on “Updated skeleton void ratio for gravelly sand mixtures considering effect of grain-size distribution”

Microstructural evolution at sand–structure interface of suction caisson subjected to lateral cyclic loadings

Suction caissons are being widely employed as a reliable and economic foundation to offshore wind farm. Previous studies are inconclusive in soil microstructural evolution around soil–structure. This article describes a half-caisson subjected lateral cyclic loading with the macro photography device (MPD). The microstructural probability entropy and corresponding quantification criterion are introduced to examine the effects of grain size distribution, grain orientation on monotonic, and post-cyclic moment capacities of suction caissons. The image-based results provide evidence of significant particle rearrangement occurred adjacent to the caisson wall. The variations of the grain size entropy and the orientation entropy with cycles were obviously affected by loading amplitudes, sand gradations, and position of the caisson interface, but less dependent with the loading frequency. Experimental results reveal the dominance of the grain size entropy over the moment capacity of suction caissons under different loading characteristics and sand samples. The half-model tests together with the MPD shed light on soil–structure behaviors with the microstructural evolution at the suction caisson interface.

Effects of dust grain size distribution on the abundances of CO and H2 in galaxy evolution

ABSTRACT We model the effect of grain size distribution in a galaxy on the evolution of CO and H2 abundances. The formation and dissociation of CO and H2 in typical dense clouds are modelled in a manner consistent with the grain size distribution. The evolution of grain size distribution is calculated based on our previous model, which treats the galaxy as a one-zone object but includes various dust processing mechanisms in the interstellar medium (ISM). We find that typical dense clouds become fully molecular (H2) when the dust surface area increases by shattering while an increase of dust abundance by dust growth in the ISM is necessary for a significant rise of the CO abundance. Accordingly, the metallicity dependence of the CO-to-H2 conversion factor, XCO, is predominantly driven by dust growth. We also examine the effect of grain size distribution in the galaxy by changing the dense gas fraction, which controls the balance between coagulation and shattering, clarifying that the difference in the grain size distribution significantly affects XCO even if the dust-to-gas ratio is the same. The star formation time-scale, which controls the speed of metal enrichment also affects the metallicity at which the CO abundance rapidly increases (or XCO drops). We also propose dust-based formulae for XCO, which need further tests for establishing their usefulness.

Deeper insights into dodecahedron distortion and microwave dielectric properties of Y3-xRxAl(Oct)2Al(Tet)3-xSixO12 (x = 0.1–0.5; R = Mg, Ca) garnet-type ceramics

Y3-xRxAl(Oct)2Al(Tet)3-xSixO12 (x = 0.1–0.5; R = Mg, Ca) ceramics were prepared via solid-state reaction method. The effects of Mg2+ (∼0.89 Å) and Ca2+ (∼1.12 Å) substitution at the dodecahedral site for Y3+ (∼1.019 Å) on the microstructure, crystal structure and microwave dielectric properties of Y3-xRxAl(Oct)2Al(Tet)3-xSixO12 garnet ceramics were investigated and discussed using the P–V-L theory, Raman spectrum, bond valence theory, Terahertz time-domain spectroscopy and infrared reflectance spectrum. Different from normal garnet structure of ceramics, the dielectric constant is abnormally increased in Y3-xMgxAl(Oct)2Al(Tet)3-xSixO12 (x = 0.1–0.5) ceramics due to the increase of ion polarizability caused by the rattling effect. There is a dependence of bond energy, bond valence and dodecahedral distortion on τf value, which provides new possibility for tuning the temperature coefficient of garnet ceramics. There are strong effects of grain size distribution, average lattice energy, packing fraction, FWHM of Raman peak on their Q×f values of Y3-xRxAl(Oct)2Al(Tet)3-xSixO12 isostructural ceramics caused by the difference of Mg2+ and Ca2+ ionic radius. Above work provides deeper insights into the understanding of the microstructural characteristics and performance relationship of garnet-type microwave ceramics, and lays a foundation for future applications in the 5G/6G frequency bands.

Effect of grain size distribution of blasted rock on WK-35 shovel performance

Effect of grain size distribution of blasted rock on WK-35 shovel performance

Grain-Size Distribution Effects on the Mechanical Behavior of Granular Soil in Response to EPBS Tunneling

Grain-Size Distribution Effects on the Mechanical Behavior of Granular Soil in Response to EPBS Tunneling