Volume Fraction Of Component Research Articles

Physics of hardening of the rolling surface of rail head from hypereutectoid steel after operation

In Russia, with its extensive railway system, for more than 5 years, special-purpose rails of increased wear resistance and contact endu­rance of the DH400RK category were produced from steel with a carbon content >0.8 %. On the head rolling surface of differentially hardened long rails made of hypereutectoid steel after long-term operation, transmission electron microscopy methods revealed the morphological components of the structure: lamellar pearlite, fragmented pearlite, destroyed lamellar pearlite, globular pearlite, completely destroyed pearlite, subgrain structure. The contribution of hardening due to: lattice friction, solid solution hardening, pearlite hardening, incoherent cementite particles, grain boundaries and subboundaries, dislocation substructure and internal stress fields were quantified. A hierarchy of these mechanisms was made and it was noted that for the fillet surface of the rail head, the main hardening mechanism is hardening by incoherent particles, as well as mechanisms caused by internal long-range (local) stresses, internal shear stresses (“forests” of dislocations) and substructural hardening. For the rolling surface along the central axis of the rail head, the main role in hardening belongs to long-range stress fields (especially its elastic component), hardening by incoherent particles and substructural hardening. Taking into account the volume fractions of the morphological components and their yield strength, the additive yield strength on the head rolling surface in the center and on the fillet was determined: 7950 and 2218 MPa, respectively. The paper presents a physical interpretation of the difference in values of the additive yield strength on the rolling surface of the rail head in the center and on the fillet.

Rain Drop Motion in an Atmosphere Containing Aerosols Particles

A mathematical model is constructed for the dynamics of a raindrop moving in a gravity field through an atmosphere containing fine particles, taking into account the processes of relaxation of its velocity and the capture of fine particles. It has been established that the equation of motion of a drop in the problem posed belongs to the class of singularly perturbed equations, for the integration of which it is necessary to involve special algorithms. In the limiting modes of droplet motion, analytical solutions of the problem are obtained that describe the dependence of the droplet velocity and coordinate on time. In the complete formulation, the solutions of the problem are obtained numerically for different values of the defining parameters. The influence of the droplet size on the parameters of its motion in a concentrated aerodispersed mixture has been studied. The dependences of the limiting volume fraction of the solid component in the composition of the drop and the intensity of the precipitation of particles (washed out by the drop) on the earth’s surface on the size of the drop are obtained. Comparison of the calculated, approximate-analytical and experimental dependences of the steady-state rate of fall of a drop on its size was carried out, which showed their good agreement.

Analysis of the Effect of Sampling Probe Geometry on Measurement Accuracy in Supersonic Gas Flow

The accuracy of sampling of gas components has a significant impact on the measurement of various performance parameters in the combustion chamber of an aero-engine. In order to investigate the effect of the probe geometry of a six-point gas sampling probe on sampling accuracy in supersonic gas flow, a three-dimensional probe gas flow characteristic solution model is established through numerical simulation methods of components of transport and fluid–solid coupling. Probes with three angles of 28°, 30°, and 32° and an optimized conical probe are constructed. The sampling accuracy of the probes with different geometries is compared and evaluated by the deviation of the component volume fraction before and after sampling and the resulting combustion efficiency error. This paper presents a set of calculation methods for solving the relative deviation of volume fraction by an iterative method based on the ideal gas law and the Redlich–Kwong equation (R-K equation). The method is designed to solve the exact component volume fraction problem in the simulation calculation. The study results demonstrate that the 28° and optimized conical probes improve sampling accuracy more effectively than the original 30° structure. The deviation of the volume fractions of the two structures is less than 1.7%, and the combustion efficiency error is less than 0.09%. The developed iterative calculation method can significantly reduce the theoretical calculation error to less than 0.06%. The experimental data of the test bench are in good agreement with the simulation results, thereby demonstrating the reliability and accuracy of the sampling probe following structural optimization.

Effects of annealing time on microstructural characteristics and mechanical properties of cryo-rolled CoCrFeMnNi high entropy alloys

High-entropy CoCrFeMnNi alloy was subjected to cryo-rolling with a reduction ratio of 25 % and was then annealed at 1050 °C for 5, 25, and 45 min. The results of the recrystallization textures of the various annealed samples showed the presence of similar texture components, indicating that cryo-rolling had only a limited effect on the formation of the subsequent annealing texture. The volume fractions of the different texture components similarly showed no obvious dependence on the annealing temperature. The uniformity of the recrystallization texture suggests the absence of strong preferential nucleation and growth during annealing. The cryo-rolled samples processed with different holding times exhibited a remarkable ambient temperature strength-ductility combination.

A Balancing Act: Experimental Insights into the Volume Fraction of Conductive Additive in Lithium-Ion Battery Electrodes

Lithium-ion battery electrodes are traditionally comprised of a cathode or anode material, a carbon conductive additive, and a polymeric binder. The conductive additive and binder are traditionally considered electrochemically inactive; however, the organization of the carbon-binder matrix in 3D space significantly alters electrode physical properties such as electrical conductivity and porosity, resulting in changes to electrochemical performance. While many experimental studies have altered the mass fraction and type of conductive additive, this study systematically studies the volume fraction of electrode components. Electrodes composed of lithium titanate (LTO) active material and SuperP conductive additive across six different electrode compositions from 20–70 vol% LTO and three different electrode film thicknesses of approximately 70, 125, and 225 μm were evaluated. Electrode structures were observed via scanning electron microscopy and electronic conductivities were measured with 4-point probe analysis. Notably, electrochemical performance described as different figures of merit are maximized for different electrode compositions. For example, while thin electrodes with maximal volume fractions of LTO achieve superior volumetric energy density, power density is maximized for thicker electrodes with an optimal volume fraction of conductive additive. This study demonstrates the importance of balancing overpotential arising from ohmic drop and concentration polarization.

Phase Fraction Estimation in Multicomponent Alloy from EDS Measurement Data.

To perform quality assessments of both metal alloys and many other engineering materials, measurements of the volume fractions of phases or microstructure components are utilized. For this purpose, quantitative analysis of the evaluated components' distribution on metallographic specimens is often employed. Phases or components of the microstructure are identified based on the variation in signal received in the band of light seen. Problems with the correct identification of measurement results in this spectral band can be caused by the inhomogeneity of the etching when the alloy components are segregated. Additional uncertainty arises when the analyzed image pixel contains a boundary between grains of different phases. This article attempts to use the results of local chemical composition measurements as a source signal for quantitative evaluation of phase composition. For this purpose, quantitative maps of elemental concentration distributions, obtained with a Tescan Mira GMU high-resolution scanning electron microscope in QuantMap mode, were used as input data for the phase composition evaluation of an EN AC 46000 alloy sample. The X-ray microanalysis signal generation area may contain grains of more than one phase. Therefore, evaluation of the phase fractions in areas of individual measurements were calculated by looking for the minimum of the objective function, calculated as the sum of the squares of the deviations of the results of measurements of the concentration of individual elements from the weighted average values of solubilities of these elements in the phases.

Effects of phantom microstructure on their optical properties.

Developing stable, robust, and affordable tissue-mimicking phantoms is a prerequisite for any new clinical application within biomedical optics. To this end, a thorough understanding of the phantom structure and optical properties is paramount. We characterized the structural and optical properties of PlatSil SiliGlass phantoms using experimental and numerical approaches to examine the effects of phantom microstructure on their overall optical properties. We employed scanning electron microscope (SEM), hyperspectral imaging (HSI), and spectroscopy in combination with Mie theory modeling and inverse Monte Carlo to investigate the relationship between phantom constituent and overall phantom optical properties. SEM revealed that microspheres had a broad range of sizes with average and were also aggregated, which may affect overall optical properties and warrants careful preparation to minimize these effects. Spectroscopy was used to measure pigment and SiliGlass absorption coefficient in the VIS-NIR range. Size distribution was used to calculate scattering coefficients and observe the impact of phantom microstructure on scattering properties. The results were surmised in an inverse problem solution that enabled absolute determination of component volume fractions that agree with values obtained during preparation and explained experimentally observed spectral features. HSI microscopy revealed pronounced single-scattering effects that agree with single-scattering events. We show that knowledge of phantom microstructure enables absolute measurements of phantom constitution without prior calibration. Further, we show a connection across different length scales where knowledge of precise phantom component constitution can help understand macroscopically observable optical properties.

Tensile strength of particle reinforced composite with interfacial debonding

Strength prediction of a particle reinforced polymer composite (PRPC) is still challenging. Although a PRPC is overall isotropic, it is more difficult to predict its tensile strength accurately than a continuous fiber reinforced composite (CFRC). One reason for this difficulty is that the calculation of stress fields of the constituents in a PRPC are complicated. The other reason is that the strength of a PRPC is significantly affected by interfacial strength, which is hard to be measured directly. In our research, the discount of the composite strength after debonding is attributed to the intensifying stress concentration. Two stress concentration factors (SCFs) are derived respectively to characterize the stress fluctuations in the matrix caused by the embedded particle before and after debonding. Based on the micromechanics Bridging Model and the matrix true stress theory, these two SCFs can be applied to evaluate the interface strength and the ultimate tensile strength of the composite from the properties of its component materials. Illustrations are presented to verify the efficiency of our theory and analyze the main influencing factors on the strength of the PRPC, including mechanical properties of component materials, particle size and volume fraction.

Broadband low-frequency sound insulation of stiffened sandwich PFGM doubly-curved shells with positive, negative and zero Poisson's ratio cellular cores

Compared to the conventional cellular cores, the cellular cores auxetic metamaterials with negative and zero Poisson's ratios have unique mechanical deformation characteristics, which can be further applied to modeling lightweight sandwich structures. Based on that, the sound transmission characteristics of a novel stiffened sandwich porous functionally graded materials (PFGM) doubly-curved shells with full Poisson's ratio characteristic range cellular cores are investigated in this study. The adjustment of material properties of PFGM face sheets in the thickness direction is achieved through power law based on component volume fraction, and the core layer consists of cellular cores with positive, negative, and zero Poisson's ratios (PPR, NPR, and ZPR). Two common types of stiffened sandwich shell types, namely, the shell with PFGM face sheets and metal-rich cellular cores (type-A), and the ceramic-rich cellular cores (type-B), are discussed, and the Hamilton's principle is used to derive the governing equations. By applying normal velocities continuity conditions at the fluid-structure interface to consider fluid-structure coupling, which is further analytically solved using Navier's technology, and the average sound transmission loss (STL) with broadband low-frequency is described. The effectiveness of the established theoretical model is confirmed by comparing it with previously published results, experimental and simulated results obtained by impedance tube and COMSOL commercial software. A systematic comparison is conducted on the performance of stiffened sandwich PFGM doubly-curved shells with full Poisson's ratio characteristic range cellular cores, and the results show superior performance in the sound insulation for the sandwich shell with ZPR cellular cores, considerably at a broad low-frequency range of 220–2040 Hz, in comparison with the sandwich shell with NPR cellular cores and conventional PPR cellular cores types. This work's findings can serve as a benchmark for future studies and help to design and create engineering sandwich structures with improved sound insulation properties.

Difference in the structure and morphology of CVD diamond films grown on negatively charged and grounded substrate holders: Optical study

Microcrystalline diamond films were grown by plasma-enhanced chemical vapor deposition from a CH4/H2 gas mixture on Si single-crystalline substrates placed on negatively charged and grounded substrate holders. The obtained diamond films had the (100) predominant faceting of microcrystals. The film structure and morphology were analyzed by scanning electron microscopy, photoluminescence, Raman and FTIR spectroscopies. The main physical factor causing the difference in the structure of the diamond films grown on the grounded and charged substrate holders was found to be the flow of low-energy (up to 200 eV) Si+, N2+, H, O ions in the latter holder. These ions predominantly embedded into the structure of the diamond films grown on the charged substrate holder leading to appearance of residual mechanical stress up to 2 GPa. Ion bombardment led to increase in the volume fraction of non-diamond carbon component in the film grain boundaries, decrease in sp3-bonded carbon fraction and reduction of the diamond microcrystals lateral size. Larger amount of grain boundaries in the diamond films grown on the charged substrate holder promoted diffusion of Si atoms from the substrate to the plasma and growing film surface, inducing formation of SiV centers in the diamond microcrystals even in the 150…200 μm thick films. The concentration of Si-related defects was much smaller in the films grown using the grounded substrate holder. These films had substantially smaller volume fraction of graphite-like carbon in the grain boundaries and were more homogeneous.

Prediction of Thermo-Mechanical Properties of 8-Harness Satin-Woven C/C Composites by Asymptotic Homogenization.

The elasticity matrix and the coefficients of thermal expansion (CTEs) of 8-harness satin-woven (8HS) carbon-fiber-reinforced carbon matrix (C/C) composites at high temperatures were obtained by the asymptotic homogenization method (AHM) and finite element method (FEM). By analyzing the microstructure of the 8HS C/C composites, a representative volume element (RVE) model considering a braided structure was established. The effects of the temperature and component volume fraction on the elasticity matrix and CTEs of the composites were investigated. The sensitivity of model parameters, including the size of RVE model and mesh sensitivity, were studied. The optimal calculation model was employed. In addition, the effects of the 4HS methods and 8HS methods on the elastic constants of the composites were compared. The temperature and variation in the carbon fiber volume fraction were found to have a significant impact on the elasticity matrix and CTEs of composite materials. At the same volume fraction of carbon fibers, some elastic coefficients of the 4HS composite material were slightly lower than those of 8HS composite material. This research affords a computational strategy for the accurate prediction of the themo-mechanical properties of satin-woven C/C composites.

Which Lipid Nanoparticle (LNP) Designs Work? A Simple Kinetic Model Linking LNP Chemical Structure to In Vivo Delivery Performance.

Although lipid nanoparticles (LNPs) are the predominant nanocarriers for short-interfering RNA (siRNA) delivery, most therapies use nearly identical formulations that have taken 30 years to design but lack the diverse property ranges necessary for versatile application. This dearth in variety and the extended timeline for implementation are attributed to a limited understanding of how LNP properties facilitate overcoming biological barriers. Herein, a simple kinetic model was developed by using major rate-limiting steps for siRNA delivery, and this model enabled the identification of a critical parameter to predict LNP efficacy without extensive experimental testing. A volume-averaged log D, the "solubility" of charged molecules as a function of pH weighted by component volume fractions, resulted in a good correlation between LNP composition and siRNA delivery. Both the effects of modifying the structures of ionizable lipids and LNP composition on gene silencing were easily captured in the model predictions. Thus, this approach provides a robust LNP structure-activity relationship to dramatically accelerate the realization of effective LNP formulations.

The effect of microfabric heterogeneity on shear wave properties in fine-grained sediments

The water-sediment interface is highly susceptible to physical, biological, and chemical processes, which can create significant levels of heterogeneity in sediment biogeoacoustic properties at various spatial scales that affect transmission and scattering of elastic waves. Using a suite of microscopy, spectroscopy, and medical sonoelastography techniques, relationships between heterogeneity in the sediment microfabric and shear wave speed can be investigated at spatial scales ranging from centimeters to micrometers. Here, we study fine-grained sediments extracted from two unique intertidal mudflats in the Great Bay Estuary, New Hampshire, USA. Shear waves were excited via acoustic radiation force and external vibration in the 50–200 Hz frequency band, and particle velocity was sensed in the top 2 centimeters of sediment at approximately 0.5-micrometer spatial resolution using a research-grade medical imaging array. By directly imaging the propagating shear wave, spatial heterogeneity of shear wave speed was directly measured. Next, subsamples were extracted and prepared for microscopy, where volume fraction and orientation of organic, mineral, and aqueous components were studied at various spatial scales. A comparison of between shear wave speed and microfabric parameters will be presented. [Work sponsored by ONR.]

Influence of pressure on the results of measuring the volume fractions of gas components using Raman spectroscopy

Influence of pressure on the results of measuring the volume fractions of gas components using Raman spectroscopy

New strategies based on liquid phase sintering for manufacturing of diamond impregnated bits

Infiltration is an extensively used technique in the production of Diamond Impregnated Bits (DIBs) commonly used for drilling in both mineral exploration and the Oil&Gas industry. This paper describes research into liquid phase sintering (LPS) as an alternative to commonly used infiltration processes. The great wear resistance and high cutting ability necessary for these tools in turn requires a high diamond concentration and a large volume fraction of wear-resistant components, such as tungsten carbide and/or eutectic tungsten carbide particles. With relatively large particles that do not contribute to densification, the LPS system researched was designed with a relatively large amount of permanent liquid phase sintering, with, rearrangement being selected as the primary densification mechanism owing to the stability of the hard phases. After testing various binder phases and evaluating the influence of the liquid phase volume fraction and presence of some sintering aids, results are promising. Bonds with better sintering behaviour were characterized, while hardness, microstructure, abrasive wear resistance, and interaction with diamonds were studied. The proposed 35NiP25Cu40WC bond processed by LPS attained hardness of 66 HRA and wear coefficient of 20 mm3/MPa, levels similar to those obtained by hot pressed components currently used in the diamond drilling tool industry (19 mm3/MPa).

A Dissolvable Micromechanics Model for Composites

This paper proposes a novel micromechanics model tailored for dissolvable composites, where the inclusion undergoes dissolution and diffusion within the matrix, with the aim of analytically predicting the time-dependent properties of composites. The dissolution of inclusion leads to a reduction of its volume fraction and the formation of a growing interphase layer around the inclusion. This versatile model is applicable to both short-term dissolutions, as observed in the fabrication process of composites and long-term degradation occurring in high-temperature or corrosive environments, common in industrial and biological applications. Dimensionless expressions for time-dependent volume fractions of composite components are related to the dissolution and the diffusion rates, and a micromechanics three-phase model is established to evaluate the properties of the composite as a function of dissolution time. A detailed parametric study is performed to demonstrate the effect of all the parameters on the final properties. The model is successfully applied to the experimental data in the literature to show its capability and flexibility in predicting the practical dissolution examinations. The introduced model provides a pioneering framework for the future evolution of the dissolvable micromechanics concept.

Discovery of asymmetric distribution of fine particles in fluidization using signal deflection reconstruction measurement

Bubbles in fluidization contribute to efficient gas–solid interaction and excellent transfer behavior. The fines addition effectively improves fluidization quality by prioritizing bubble control. Our study delves into the dynamic behavior of these added fines through cold-flow fluidization experiments, employing coarse glass particle (Geldart Group B, 186 μm in diameter) with varying contents of fines (Geldart Group A, 60 μm in diameter). To overcome the challenge of measuring the solid volume fractions of individual components in this bi-disperse system, a novel measurement technology, coupled with an optical fiber probe and signal deflection reconstruction method, is established. This technology could sensitively capture the preferential entry of fines into bubbles, leading to an asymmetric distribution of fines between bubbles and emulsion phase. Furthermore, our proposed flux mode, considering both the capability to maintain mono-disperse phase segregation and the competitive occupation of bi-disperse particles through bubble interface, effectively describes the observed asymmetry.

Constitutive model for hot deformation behaviors of Al/Cu bimetal composites based on their components

The hot deformation behavior of Al/Cu bimetal composites was investigated using isothermal compression tests at temperatures of 400–500 °C and strain rates of 0.001–0.1 s−1 by considering the effects of volume fractions of composite components (30%–51% Al). In this regard, new proper constitutive equations were developed using Arrhenius-type and the rule of mixture (ROM) models. Experimental flow stress (FS) showed that processing parameters and volume fraction affect the flow behavior of composite as the volume fraction of copper has a more substantial impact on the flow behavior of the composite rods at elevated temperatures. The values of correlation coefficient (r) and average relative error of the developed Arrhenius-type constitutive equation and ROM model were 0.9826, 0.9742 and 0.9718, and also 0.18%, 1.69% and –0.84% for volume fractions of 51%, 42% and 30% Al, respectively. The results indicate that the newly developed constitutive model can successfully predict the hot working behavior of the considered bimetal composite. Finally, the microstructure of composites was investigated under different processing conditions. The dominant mechanisms for three considered volume fractions were identified at different temperatures, strains, and strain rates specified for the hot deformation of the Al/Cu composite.

Computational fluid dynamics analysis of a novel continuous cementing slurry mixer

To improve the uniformity of continuous slurry mixing in well cementing, a novel continuous mixing system is proposed in this paper. The CFD model of the mixing system is established by employing the Eulerian multiphase flow model, k-ε model, and Multiple Reference Frames (MRF) method to simulate the flow of the two-phase fluids and the rotation of the agitator, respectively. A segmented control simulation method, which includes a dynamic “monitoring-assignment” approach capable of handling secondary mixing processes in engineering, is proposed to calculate the slurry mixing process in the continuous system. A comparative analysis of the control effectiveness is conducted to demonstrate the feasibility of this method. Using the validated model and method, the mixing process of the slurry in the system is investigated. The obtained data is analyzed based on four indicators: uniformity calculation, power, velocity component, and solid volume fraction, to evaluate the effects of impeller diameter and rotational speed on slurry uniformity. The data shows that both impeller diameter and rotational speed significantly affect the slurry uniformity in the continuous mixing system, while only impeller diameter has a greater impact on the flow field and flow pattern inside the stirred tank. It is observed that increasing the impeller diameter and rotational speed beyond a certain point does not further improve slurry uniformity, and excessive impeller diameter and rotational speed may lead to a decrease in uniformity due to stratification in the tank, along with a significant increase in power consumption. The proposed novel structure and method can provide valuable references for the industry, and the research findings can offer scientific guidance for achieving efficient well cementing operations in engineering.

Graphite-assisted microwave carbon dioxide gasification of wet stalks

In order to realize the low-carbon gasification of the typical wet stalks, the graphite was used as the microwave-absorbing agent and the heat transfer medium in the microwave field, and CO2 was used as the gasification agent to explore the characteristics of microwave CO2 gasification. After mixing the corn stalks, the rice stalks or the wheat stalks with different water contents and the graphite in a mass ratio of 4:1, CO2 was introduced for gasification in a microwave field. Experiments showed that with the increase in the water content, the carbon conversions, the gas yields and the volume fractions of the effective components all increased slowly in the front and rear sections, and increased rapidly in the middle section. When the CO2 flow rate was 0.6 Nm3·kg−1·min−1, the carbon conversions, the gas yields and the volume fractions of the effective components all reached their peaks. It was found that the structure of the three stalks changed from smooth to porous during the intermediate process of the graphite-assisted microwave gasification. The deashed stalks with water content of 60 % was gasified in a microwave field of 700 W for 1.25 min, and the BET specific surface areas of the generated porous carbon reached 2041–2054 m2 g−1, and the volume fractions of the effective components of the gasification gas were more than 95 %. With the prolongation of the gasification time, the carbon conversions increased slowly in the early and late stages, but increased rapidly in the middle stage. The reason was that the large amount of porous carbon generated in the middle stage was the gasifiable strong microwave-absorbing agent, which greatly increased the gasification temperature and accelerated the reaction rates. When the graphite was reused 10 times, the carbon conversions could still reach more than 80 %. The XRD tests were carried out on the graphite used many times to explore its deactivation mechanism. This paper has practical significance for the low-carbon CO2 recycling of stalks biomass, and provides a new way for the preparation of biomass-based porous carbon.